Jennys280Z

Thank you Eurodat we got a new carpet with extra insulation in the hatch for noise reasons last year which doesn't help now that I'm trying to hear noise again, dont think I want to hear it through polyurethane though. A 2nd quick test drive and a vacuum test is showing 19 inches. There's a vault of information on here about every problem. I'll get under the car when the weather cools down a bit (95-100 lately). J's really looking forward to driving the car next month. Don't want to take the thread off-topic too badly so I will let this dead cylinder thread close with a successful result. You guys are the best thanks again Sean

Zed Head, sorry about the confusion. Yep I hijacked her account. At first, I did create a new account name "1976280Z" at first to avoid confusion but never got the verification email. Nothing in spam folder. Then we couldn't remember the username/password until I got back to her place last Sunday and her password was still in the browser cache on her old desktop. She's out of state in grad school atm and gave up on the car before that because she didn't have the time or money to put into it. She was considering selling it for a time but when we couldn't agree on what "fun" car to eventually own, and then the car started to grow on me over time. I think it still has a lot of potential to be a great car but it's not even close yet imo. I used to own a 442 and worked on that myself but the Datsun has been more interesting to work on after all the stories she's had to tell about it. So it's the same car and still hers, I've hijacked the car too in the meantime. She's consulting from afar and referred me here. She mentioned you specifically too Zed Head and a few other ppl I forget and that you guys have saved her hundreds if not thousands in labor cost. Your ID on the slip yoke is probably dead on because it does have the "clunk" when accelerating in gear from a standing start especially. J said this was an issue years before the car went into hibernation. A local Z shop specialist at the time acted like he didn't know what making the noise exactly, remarked about the U-joints but she can't remember what he said exactly. Either she couldn't afford the repair, or the guy didn't want to do it or couldn't do it, or ...

Thanks Chas I'll go with one of those two brands. Just read other classiczcar threads on doing this job...looks like all my questions are answered at this point. But the diff oil prob ought to be changed too. Looks like my labor just doubled

Well I kept the same old battery but I charged it till it hit 12.65V then installed it quickly and started the motor right away. Maybe it wasn't electrical and the injector was physically stuck. It's hard to think that a voltage issue would have affected one injector completely when some of the other connectors looked just as bad or worse. I didn't put any of the metal clips back on and I suppose this is okay? I do want to pull the connectors in about three months and inspect them...maybe when they get this old the corrosion becomes more of an issue faster and have to apply some regular TLC not to have problems. The motor felt so strong now that the clutch feels like it's having more issues...vibration or just noise coming from below the center console. When the car was garaged and not running for nine years or so, all the brake cylinders were toast but the clutch cylinders are still hanging in there. I changed the fluid but it turned black almost immediately so there's a lot of corroded rubber probably coming from the master cylinder. The slave cylinder and hose were replaced in '89 but I think the master is the original from '76. So now that the motor's done (never done really, ready to install a new oil sending switch but I'm reluctant that it might be seized in the block) I'll move to the clutch and I'd like to change the transmission fluid too...planning on jacking up the front to drain it, jack up the back to fill it. Lower the back to drain excess fluid out, then jack up the back again to tighten the fill plug. If all this doesn't make the car happy I'll have to start saving for the transmission fund. It was actually Blue's comments about the current producing a magnet moving a slug allowing the injector to spray gave me the tapping idea. The alternator is original...still hanging in there. Jennie thinks there's a broken bolt in the front of it, we'll need a pro to do that since we don't have any kits to extract bolts (or experience). Happy that the engine runs so smooth now.

For posterity, I actually did have to tighten up the idle adjuster quite a bit. I had an idle of over 1100 warmed up. I settled it down to about 850 and the screw actually feels 'tight' now. The vacuum was already healthy on five cylinders. It must be super healthy now. I must have been enjoying the ride too because I caught myself going 65mph in a 35 zone. Actually an oncoming car was flashing his brights at me so I must have looked like I was going really fast. And only then did I check the Speedo. That slowed me down too, since the bro-code for cops is flashing your brights, after all.

Feels like 30 horsepower! The moment I touched the gas pedal after backing out of the driveway it was immediately obvious. I tapped on the #3 injector about a few hundred times with the plastic end of a screwdriver, and even more uselessly, tapped on the fuel pressure regulator a few dozen times as well. In a really old video from "Big Phil" from HybridZ (turbo280Z on Youtube) he mentioned that a Z mechanic told him he could raise the fuel pressure in the fuel rails temporarily by tapping on the regulator. I'm sure it's a useless idea to make your car faster, but having some extra psi in the fuel rails couldn't hurt when I'm trying to unstick or upvolt an injector. The 2 & 3 wires are still swapped; I suppose I'll swap them back to their proper injectors again. I'll be left having to wonder: Was it physical or electrical or a combination of the two? I question that maybe it was a combination of the two. I brushed the female connectors like a mouth full of cavities in between several soakings with Caigs. Jenn said she cleaned the injectors but they all still looked pretty corroded to me. Looking at the spark plugs again, cylinders 2, 4 and 6 all show lean running conditions so I cleaned #4 and 6 before the test drive. #2 was already cleaned as the test cylinder, and #3 was of course dead which got cleaned first. I've got the battery unplugged for now and I might as well clean #1 and 5 too, which looked like the healthiest of my spark plugs by far. Time for the clutch hydraulics. I might be pining for more help in that forum in the next week or so. I'll know more for sure after the clutch work is done whether the transmission has seen its better days. I'm interested in a remanufactured 5-speed from a '77 or '78 280 that has the same ratios as the one I've got now and is plug and play with my stock motor. Thanks again for the pro advice you guys. I wouldn't have been able to do it without you guys. Special thanks to Blue; your wisdom was golden.

Siteunseen I was reading through an older thread about you going with the FJ707ts and I wondered how you were getting along these days. Good to hear you're alright. Thanks Blue, it was wishful thinking that something was just plugged in wrong. Thanks all, I'll look into the more affordable EFI parts for sure. Got the injectors swapped but haven't had time to run the motor yet. I'd be out there right now driving it around but I don't want to wake up the neighbors. Damn you, Flowmaster! So instead I decided to replace my old battery with a brand new one tonight, until I learned that Autozone has nerfed their Duralast Gold batteries sometime earlier this year. My old equivalent size-24 "DLG" battery has 750 CCA, the new replacement DLG with an "S" added to the part number comes in at only 575. Then he had to switch stickers on the two batteries to make mine look like his, because he already ran the swap through the system before I decided to do it and it was somehow irreversible. So when I go back to Autozone in a few years to replace the battery again it'll look like I swapped it already tonight when I didn't. But at least it'll have that "S" on there so there's no chance of a problem. The last straw was his $2000 battery tester was outputting some crazy numbers on all of the 24's he had left and it was the only tester he had. Leaving with an inferior battery was bad enough already. Leaving with one that wasn't even known to be good was too much to ask for. Interesting how a battery with 11.99V or 12.4V between the posts can be in a highly discharged state. I thought the relationship between battery voltage and its state of charge was pretty basic or linear, but I learned there's no accurate way I can tell what the charge percentage is from a volt/multimeter. I wonder if people just wing it, or keep charging their battery till they see 12.xx V, or if the car still starts with the old battery they don't even stress it? I read some articles online last night about discharged batteries and one said that they can cause phenomena like injectors not opening, hmmm. The same article also said that running voltage will be a few volts higher than battery voltage, implying that the battery voltage still provides a baseline voltage even after the car is running? It seems the more I read online and discuss with a sales clerk, the more conflicting info. I get. It would seem that if the alternator is okay and the motor is running, the battery voltage has nothing to do with it, but it seems even more that the battery still does, and so the alternator functioning correctly is more a matter of charging the battery effectively. It also appears that I lose between 0.5-1.0V from the battery after installing it in the car, even still testing voltage between the posts. Normal or not, neither the sales guy nor me know for sure. On the bright side, my new tool set included a 10mm deep socket that makes taking the battery on and off a cinch now compared to the knuckles and cussing required with an open end wrench. When I know I'm not going to be driving the car for a while, I'm just going to leave the negative cable disconnected most of the time and see if that "solves" the discharge issue. Thanks again for all the help! This site is the best Z clinic on the internet hands down. Yes, we owe it money, I acknowledge that.

I'm going to swap connectors #2 and #3 which look like there's enough play in the wires to swap them. I wired up a 9V battery to test with that real quick but I'm going to run the motor with the swapped connectors first before I do anything else that may put gasoline on the spark plug and possibly muddy/confuse my results. So I assume either there will be a pristine dry spark plug coming out of #3 or #2. And hopefully neither because I just cleaned the connectors thoroughly with some sandpaper and some Caigs D5 on the male side and a wire brush and Caigs on the female and they're looking better now. #3 is pretty hard to reach, and even see with the fuel regulator and plumbing in the way but it's hard to think that just cleaning would make the difference between a completely dead injector and a normal one. So I doubt I'll luck out like that, and I'm not really gung-ho about actually fixing this problem ourselves whichever one it turns out to be. At the very least I'll diagnose it and we'll have a handle on what needs to be done. I'll use the stethoscope too while the motor is running to try to hear who's not clicking between #2 and #3. To answer one of my questions above, the connectors ARE keyed. It might be possible to plug them in backwards, but it'd be obvious because the top side doesn't look anything like the bottom (though the two shorter sides are visually the same) which is hard to tell until you actually take one off. The bottoms have most of the plastic cut off to fit along the curved surface of the injector. I see new injectors are $380 at MSA, and it's recommended that all six get replaced together. New connectors are also similarly priced. Labor would probably make this easily a $1,000 job no matter what parts we need. So many pros here but I doubt you'd have the patience for a hundred bad questions if we attempted a DIY. Another problem is I don't know any pro mechanics I would trust implicitly with this job. There's a Z specialist across town but I told them what year my car was and what problems I was having and they didn't even want to touch it. Fuel injection and no scanners? Eww Yuck!! It seems too many real mechanics are spoiled with OBD2 now. A Toyota specialist nearby didn't even want to look at our third generation Camry with OBD1. He actually implied on the phone that I just get a new(er) car.

Update: Sounds like the consensus is a fuel injection issue. I have to agree with this. No evidence of ignition issues, and after all, if the plug wasn't firing and the injector was functioning, I'd expect at least some gasoline on the plug, not a bone-dry-new one like that. Looking at some old notes, when Jenn was cleaning the injector connectors she broke a small piece of plastic off of the rim of the #3 injector connector. It must have been just barely hanging there with a spot of glue or else it wasn't completely broken off yet. The instant I touched the metal retaining clip with a tiny screwdriver the piece of plastic went flying and landed on the heat shield. At least when things go flying in these old cars we have a reasonable chance of finding them. Plastic or rather the lack of it is another one of the benefits of these older cars, guess I can't escape it all the time unfortunately. But would something as simple as this cause a total malfunction of the injector? And I'm guessing from the replies it's impossible to plug these things in backwards? Seriously doubt something like this really cause a total injector failure? The connector seemed to be plugged in normally and held tight by the clip; I would think this wouldn't make any difference. Just a strange coincidence... The contact surface of the connector itself is probably looking a lot greener than it should. The male connectors on the injector itself don't look too bad. I was rigging up some wire on a 9V battery but maybe I'll swap two nearby harness connectors instead. If the problem moves to another cylinder it's the wiring/connector and if it doesn't it's the injector itself. I've never listened to injectors with a stethoscope before so I don't know exactly what to expect to hear...hope it's easy enough to be foolproof. Pulling a brand new looking spark plug out of cylinder #2 or 4 would be the backup way to tell if I'm stetho-challenged.

Spark plugs have 60 miles The #3 plug came out looking brand new. I've pretty much ruled out some culprits below: Ignition coil: Wouldn't effect only one cylinder 100% and other cylinders not at all. Distributor: All tune-up parts almost new. Distributor cap metal contacts show the same pasty white surface wear indicating it's operating correctly even for cylinder #3 i.e. they all look identical. Spark plug wires: Almost brand new NGK set. Tested resistance on #3 wire as 5,980 Ohms which should be fine especially for a wire 2+ft long. Spark plug: Looks like it never even fired...unless it's been firing in a cylinder with no-combustion (no fuel) in air only. The center electrode does look dark and glossy. I thought it was wet with gas when I first pulled it out, but it was dry. I don't have a new plug to compare it to exactly. No odor or substance on the plug besides a very weak gasoline smell, if that. No oil in the cylinder, no antifreeze or antifreeze smell, no gasoline in the oil, no signs of any strange shorts or arcing inside the distributor, cap, wires, engine or plug. Everything in the ignition circuit looks fine, and I never saw any sign of spark blowing out or grounding improperly (at night, etc). So the inspection of the ignition system suggests that it's not an ignition problem. I've verified spark at the wire with a timing light too. I'm too scared to pull the end cap off the plug with the motor running to know for sure, Ha! Cylinder #3 compression is 140+PSI in a COLD motor which rules out any mechanical problem (rings, valves etc.) A few years ago, I did clean the fuel injector connectors. Since then I've only put about a hundred or so miles on the car. If it's possible for a spark plug to remain looking 99.9% brand new when firing in cool-ish air with no combustion, is it possible to plug the injector in backwards and thus disable the injector completely and still have this phenomenon with a plug that was sparking the whole time? The #3 injector wire is a bit longer than some of the others, there's a bit more "slack" in the wire (a bigger curve) and it's not discernable whether the wire got twisted or that the plug was installed upside down. Is this connector keyed (does it prevent one from connecting it wrong)? A webpage from AtlanticZ says that the +12V end is always closer to the front of the car. It doesn't say how to distinguish one from the other. The new pinch-style connectors look nice too http://atlanticz.ca/zclub/techtips/injectors/connectors/index.html I'm at a loss. The only other possibility I can think of is a defective spark plug (which seems like such a remote possibility it's not feasible) but is there anything else that could be causing this that I'm not thinking of? The car seems to be running good and even smooth at idle although it idles too low until it fully warms up. Starts immediately, fuel pressure is steady in the mid 30s. A hot motor has a 1000 RPM idle. Presuming it's running on five cylinders (which I have to do looking at the plug) (6/5)x = 1000RPM; x = 1200RPM implied idle speed with all six cylinders. And this kinda implies that I've raised the idle speed adjust high enough to compensate for a dead cylinder at idle. I don't want to run the motor again until I have a gameplan. I have a stethoscope and intend to listen to the injectors for the first time in a few days hopefully after some direction here? I understand I'll hear a clear buzzing sound when the injectors are opening. I'm skeptical a spark plug can come out looking this brand new firing for 60 miles without fuel. Or if someone here with more experience can verify that it's indeed possible that the ignition is fine (based on all evidence) and that it's simply a lack of fuel and combustion, I will pull off the injector connector and plug it in opposite of how I did before I start the motor again. I hope I didn't fry the ECU or at least that circuit to the ECU by wiring it backwards by accident. And if the problem is ignition, would all of the unburned gas really be going out my exhaust valve so perfectly like that, and not getting in my oil, without getting on the plug itself for that matter? I don't have the experience to know either way but I want to fix the problem without wasting too much money. Just collecting all my thoughts, I'm thinking this is a fuel problem more and more. My gut is telling me that a spark plug firing in relatively cool air with no fuel will look brand new for more miles than I put on it. Previously to this problem, or to at least to knowing about the problem, I tested the injectors at the ECU pinout and they were all showing very close to battery voltage. My battery is usually under 12V (down in the 11s) even a day after I drive it. I've either abused the battery by not regularly starting the car or I've got a drain somewhere. And not to risk stating the obvious but the injector is not leaking any fuel. I'd need even more help if it was I use Chevron 93 Octane with Techron, have treated the gas with Seafoam and in other tanks other injector cleaners prior to that, if that would make any difference to a physically clogged injector. Plugs are NGK BPR6ES Thanks! Jenn/Sean

Haynes specifies a "full flow" oil filter that should not be tightened more than hand-tight, printed in italics for emphasis. I used to tighten it more than that. Not sure how over-tightening the filter might affect pressure but I'm wondering if this is yet another reason why I was reading too low. Just based on experience the regular FRAM filters seem to be crap when (if?) my pressure was so low and the oil got dirty way too quickly. I have an XG filter from FRAM I was going to install at next oil change which are allegedly very good quality (not available in auto-parts stores around here I've been to though), but I'll take a look at NAPA Golds (or K&N) which people seem to like. Thanks for the warning FastWoman I'm really curious now how a different brand oil filter might affect what my gauge reads. x

I drove my car for years with an oil pressure gauge that barely moved. I was letting the pros fix my car at the time and if they didn't care neither did I. After resurrecting it out of the garage after 10 years in hibernation and cleaning all the electrical connectors I could find, cleaning the sender's brought the gauge back to life somewhat (at least it moved ). Upgrading my oil filter from the crappy orange FRAM filter to the Tough Guard FRAM filter increased the oil pressure substantially. It moved well off the zero after this. Now I'm getting the highest oil pressure I've ever seen since owning the car after doing a valve adjustment, but even still I've never seen pressure anywhere near half way up the gauge yet. Not sure if this is an issue to be concerned about or just a gauge that's reading low (that I've been led to believe is pretty common in the old Zs). I'm going to stretch the Z's legs with a highway drive this weekend. When I'm motoring along at a steady 3000 RPM instead of just going through the gears on slower roads, I'm curious what the gauge will read now.

My door was ajar (beeping) on some of the video, sorries! rcb280 was right again. My fan belt tightened on the adjuster arm about 3/8" of an inch when I pulled it back hard. I thought it was pretty tight already, but the torque-ier motor demanded a tighter belt. Playing the sound over and over again, I noticed it coincided with the throttle but slightly lagged the throttle so it was related but not directly related. Never heard a belt make noise like that before (it was like nails on a chalkboard to me when I heard it ) but I could visually see it slipping thanks to the white markings on the belt when I was looking at the timing again. Sorry for making so much drama over not much of anything. I was really worried though so give me a break. Thanks Fastwoman! I'm going to use the same product on my AFM cover too. I'm glad there's that nice metal base the AFM sits on or that cover would be lost on the side of the road somewhere by now. Good luck on your dock. Is this for at the end of your backyard? Looks like the two main options I can see for a distributor replacement are A1-Cardone and Autozone and they're around the same price either place. I'll check the vacuum advance again since I did it all of a couple of years ago and see if I get a similar (believed bad) result. Eurodat, thanks for taking it out of the box. I looked closely at everything I could find that was loose under the hood, and found the throttle linkage boot at the firewall as dry as toast. Just hanging on there in tatters, so I pulled it off. Not sure how I didn't see that before but it's amazing what you can see if you look hard enough lolz. Now I have a gaping hole at the firewall. I'm guessing it's to keep dust and dirt out but I'm not sure how important this is to replace (much less how the heck I can even replace it without taking the linkage apart). Thanks for helping resolve all my issues guys; you're the best! xo

Warmed it up completely tonight driving to the mall. Idle speed warmed up is still 900+ RPM even with the ignition still retarded to 9 dbtdc. A few observations on my 2nd drive after the valve adjustment... my oil pressure gauge read higher than ever today reaching close to 30 on some acceleration up hills and a still-cool motor. It stays above zero at idle now too, comforting to know I actually have some oil pressure there. To exonerate MSA, there is silicone on my AFM. I can't believe I never noticed it. It's clear and hard to spot. It's also hard. They maybe had this AFM on the shelf for awhile. I peeled the dry silicone off and the cover fits more snug now. It drove beautifully! A little bit of gas pedal goes a long way now! Docile and smooth down low but very responsive, the car actually feels easier and more forgiving to drive now post valve-adjust. On the way to the mall I heard no strange noises. Then suddenly in the parking lot on the way home from the mall, the noise returned. So I pulled it into the garage, got a sound recorder, stuck my head down to the motor and started trying to reproduce the noise and here's what happened. It sounds fantastic until I go back to the gas pedal at 1:00, I'm sticking the recorder out the window at 1:10-1:20 and the sound is clearly audible. Then once again after the 1:20 mark I'm back under the hood, revving and hearing nothing, so at 2:22 I captured the exhaust note. I never heard any weird noise for any of those revs either. <embed width="600" height="361" type="application/x-shockwave-flash" allowfullscreen="true" allowscriptaccess="always" wmode="transparent" src="http://static.photobucket.com/player.swf?file=http://vid81.photobucket.com/albums/j219/amiamelodramatist/isis_garden/photos/audio2_zpsd69ed6a1.mp4"> When I'm under the hood on the driver's side the noise sounded like it was coming from the left, towards the front of the engine compartment. Could this be a bearing in the fan/clutch? I spun the fan by hand and it felt fine. Water pump going bad, maybe? Could it be one of the pulleys up front? Oil pump? It sounds like tires losing traction on pavement when in the car driving. It makes a tinny whooshing sound at 1:15-1:20. I don't think it's pre-ignition anymore and I don't really think it's the motor based on the way the car is running. I don't see how this sound can be a valve when the whole way to the mall and 80% of the time afterwards I can't even hear it. *sigh*

I didn't have time to warm it all the way up tonight since going to 9 degrees so I'm not sure what it is, rcb. I'll go back to 10.0 degrees and no further just to be on the safe side. Thank you, it's really good to know I'm not alone. Thank you for the compliment. x

I thought 100 RPM for one degree was excessive but what do I know ....I'll advance my timing back to 10 deg and hopefully be able to blame the Sea Foam when there's no pre-ignition. fwiw the mechanical advance returned back to 9 quickly when I let off the throttle tonight so the plate isn't stuck. I think I've had a successful outcome on this issue and would like to thank everyone again, classiczcars' guys and gal.

Update: Before starting the motor I retarded the dizzy's timing a little and filled up with pure 93 octane gasoline, and the noise is gone! Revved it up 30 or 40 times and never heard it once. I have to conclude that the awful noise was pre-ignition (shaking BBs in a coffee can) vs detonation ("tump tump tump"). And what I thought was a great job on the valves is looking likely again I think it's interesting that after my AFM cover fell off and as I was putting it back on with the motor running, I noticed the hollowness of the potentiometer chamber which seems to resonate when the AFM cover is loose (e.g. not sitting flush on all edges) with the motor vibrations. The AFM from MSA is great, (it measured right what it should on the ohmmeter before I installed it) but the front cover has always been loose. That was nice at first while I was continuously going in there. But now that my mix is nearly ideal I need to think of a long-term solution to keep it from making noise or even falling off. What do you 280 folks do to secure your AFM covers? According to the timing light, timing was retarded about one degree to ~ 9.0 advance. Not sure if I should stay here or return to 10 now that the Sea Foam is gone. Bad news, cold idle isn't as high as it was. I used to warm up at 800-900 RPM and now I'm warming up at 700-800. Timing? The lack of Sea Foam? Or is this typical of S30s? No matter what, the motor sounded silky smooth and that's what matters most. Special thank you to Zed Head for responding to my noise and stopping the damage before it happened. Now for some homework on leak-down tests.

Thanks so much Leon!

Nice to hear that about your pretty car siteunseen! Now that you've shaved your crow's foot you've created a much better tool than mine. I ran into a problem with #5's exhaust valve where the position the wrench needed was so far to the side the wrench head was making contact with the head bolt. That was the only one I had to break loose with a regular 17mm. So I want to shave mine now too. I will still use it for this job but hopefully not to break anything loose anymore but to torque it to spec. Hmm...I wonder how fast these valves tighten over time on average? I am also wondering about proper tuning. Is it better to improve cylinder #2's compression via fine-tuning its lash, or is it the better convention to keep the valves as close to specs as possible no matter what?

For the record, the formerly white plugs in #2 and #6 turned beige from one good drive after the valve adjustment! I retarded the timing to what should be ~8 deg-btdc. I hope this stops the detonation and gets vacuum to a steady 18mm. I'm going to do a forum search now to find what timings people are typically running on their cars!

Okay, I bet if I took a poll, the consensus on this noise would probably be "Oh you just adjusted valves? It's the valves." I would think that too if I was reading someone else's post. I'm really confident in my work though and I'd/I'll be shocked if one of the valves came loose. After meditating under the waterfall all morning my gut tells me that this is detonation. I will elaborate... Maybe a few of you guys remember back in the day when I was starting to deal with the car, I removed those hot 5-heat-rating plugs out for some 7s and advanced the timing from 10 to 12 degrees thinking that if I was running lean, these wouldn't be bad ideas in the interim. The first time out driving I came back and said I heard "crackling" under the hood. The noise in the video above is reminiscent of that sound. After adding Sea Foam, I reported that I was hearing whooshing or crackling under the hood. I highly suspect this is the same noise. My first impulse was to think this was carbon deposits burning off and causing its own detonation. If I had that big a result going from 10 to 12, my instincts are telling me to retard the timing from 10 to 8 as long as this Sea Foam is in the tank. When I burn through this gas and fill up again on pure Chevron 93 I can return to 10 perhaps. FSM recommends 8 anyway if I remember right. I suspect my car is sensitive to octane right now and has a tendency to curve advance, for whatever reason. The theory that Sea Foam lowers octane is something I would have never thought of....very interesting! I remember another day on my adventure when I hadn't run the car in months and started it up for the first time and heard popping. I drained the old gas, put new 93 in the tank and the sounds were gone. It's moments like these that made diagnosing my car so difficult. It was like a different car every time I got in and started it up. A box of chocolates...I never knew which one I was gonna get lolz FWIW before driving the car last night and hearing this noise, I poured the rest of the can of Sea Foam into the half-full tank. At the same time I also adjusted the AFM one tooth richer before driving, and it seems intuitive that having a bit more gasoline in the mix would make a tendency to detonate even more likely if the gasoline is the culprit. EuroDat, I don't see anything in the FSM. I don't want to map the curve right now while I'm not certain what's wrong with my car. If someone else has a great-running 280Z it'd be great to get some benchmarks and I'd be happy to trace my results to their curves and see how close it looks. I've been suspect of this distributor from the very beginning. The vacuum advance seems to be non-existent (clogged) for one thing. There's got to be good/rebuilt distributors for these cars floating around out there somewhere. Why can't I find any online? I know Autozone does a swap but no you'll have to pry my distributor from my cold dead hands. I don't want just anyone rebuilding/restoring it so they mess up the curve and I install it and my car runs like poopie, and my distributor is gone forever because I gave it up as a core....ummm not gonna happen Thanks you guys are the best! :)

The noise is intermittent in the video too. FWIW, I was revving the motor a lot higher than that off-video and I didn't hear any weird noises most of the time. I'm worried now because I did start hearing noises whooshing noises under the hood right after using Sea Foam in the gas. :paranoid: I'll take the cam cover off again and investigate if there's no other easier ideas that might save me from doing so. I'd like to start with #2 if it got the lowest compression and then I put a couple good squirts of oil into the cylinder about an hour before starting it.

Hi Zed Head! Uggh I tightened them all well, even went back with the wrench on all 12 nuts one final time to make sure. But if you're right, are you saying that the lash itself has gotten too loose and the valves may be slapping around and not opening very much?

I'm glad you caught yours early before any damage was done. Just like me now too I suppose! Yep I was the one you told and it turned out just like you said. I was amazed that I didn't even drop a wrench, even when I was holding two in my left hand at the same time while using the feelers with my right. :) I won't drop any names in public here but I do have a repair invoice done by a Z-shop who wrote that they adjusted my valves and that was over 15 years but less than 2000 miles ago. So if this shop DID adjust my valves, first of all they tightened them up extraordinarily tight. They also installed NGK GR5 V-power spark plugs which are too hot. They have huge projected tips on them that would risk plug-to-piston contact. Plus when valves are so tight like that I would fear the risk could be piston-valve contact! It seems like if they did the work they said they did, they turned my motor into a time bomb. They also adjusted the AFM and scolded me ("don't mess with THAT!" while pointing at the AFM, and they put some red sealer stuff around the front cover to further make the point). Well I've had my share of messing with it since this journey began to be sure, and this one is a new/rebuilt one from MSA. I sold the old one on Ebay for $90. Remember how I once thought there was a circular dent cut on the wheel that I figured was some kind of pre-marking? You guys (you and maybe either cozye or Zed) were right about that too. On closer inspection of that wheel, it had apparently been messed with multiples of times and the indentations were just from the adjuster screw pressing into the plastic! There were little "dents" all over it, I guess from mechanics trying different positions. If this is any indication of how the professionals "fixed" my car, I'm figuring out that I'm much better off doing things myself! Really like 50-75% of the reason I'm doing all this is for education and experience. I want to know my car better. If I get great results in the process, the other 25% is a bonus!

Update! Did a 2nd compression test today (cold motor again) after the valve adjustment and here are the results: Compression (psi) Cyl 1: 146 Cyl 2: 134 (144 with a few squirts of oil) Cyl 3: 153 Cyl 4: 146 Cyl 5: 145 Cyl 6: 141 What to do about #2? Is a gain of 10psi expected/normal after a few squirts of oil on a motor with 140k? Is it likely its compression rises with the others on a warm motor and gets closer to the others? Should I just keep driving it and letting the Sea Foam in the gas keep cleaning things up? Should I try loosening lash on #2 another .0005"? After the compression test, I adjusted the AFM one tooth richer. Good news is, the occasional hesitation I experienced on last night's drive was gone. Vacuum is now tested at 17-18 mm Hg warmed up. Bad news is, I have some horrible noise coming from the front driver's side (near the AFM or ignition coil). I heard it very loud climbing a hill in 2nd gear on the way out and so I turned around right away and nursed the car back. I thought it might be the motor...maybe cylinder #2 was complaining because of the oil I squirted in...maybe I forgot to do something or pick a tool up off the car....I stopped the car and just revved the engine and I heard the noise but intermittently, it was hit and miss. When I got back, opened the hood and looked in, the AFM front cover had fallen off completely and was just sitting there. I thought it might be vibration and that front cover causing the noise (is there vacuum present around the potentiometer where this cover should be sealed?). Do ignition coils make noises when they start to go bad? Do AFMs rattle if maybe the wheel isn't straight after an adjustment or something? I'll include a vid clip of the awful noise, I really hope someone can offer wisdom on what it might be! Thanks a million you guys!!! <embed width="600" height="361" type="application/x-shockwave-flash" allowfullscreen="true" allowscriptaccess="always" wmode="transparent" src="http://static.photobucket.com/player.swf?file=http://vid81.photobucket.com/albums/j219/amiamelodramatist/isis_garden/photos/2013-05-03_zps5eafb148.mp4">