'76 280Z Question on dist/manifold vacuum, dist timing, fuel pressure, brake booster

[FastWoman]

semi-sphere rubber plugs: You mean like a small rubber boot at the end of a wire, where it makes a connection? The rubber dome simply covers a terminal post. You'd simply pull it back to reveal the post. Some of them are going to be crumbly. If they are, they're not doing much anyway. Your car will run fine without them. You can protect terminal posts with a thin layer of grease if you wish.

metric tap and dye set: Available from Autozone -- about $15

I listened to your video, but I can't tell much from it. I suppose I hear random missing. I'm sure it's much different in person! I think I hear some hard puffs in the exhaust. Does the exhaust blow rather hard at idle -- much harder than on an engine that's running right. If so, then you're probably running lean.

the buzz: Probably a body rattle. Honestly, just ignore it. Pay more attention to fuel pressure.

the AFM connector: It's built very much like the injector connectors, with a little wire clip that runs around the outside. Use a small flat-blade screwdriver to catch the tip of the wire and stretch it back off of the connector. Be careful not to let it drop, or you'll have a hard time finding it!

thermostat housing: Really not very labor intensive, as long as your bolts turn freely. You don't even have to take the radiator hose off. It's one of the easier jobs on the engine.

To keep everything in perspective, you really have to be methodical in your approach. Right now you're swinging at a pinata.

Since you have the AFM open already, do this simple test: Warm up your engine as far as it warms up. Idle it. Gently nudge the AFM mechanism with your finger. Can you make the engine run much faster when nudging it in either direction? If so, then you really do have a fuel mixture issue of some sort. My guess is identical to cozye's -- a lean mixture. However, without knowing the outcome of this test, it's only a guess.

If your mix is wrong, the diagnosis will take a more methodical approach. You're really going to have to follow diagnostic steps like cozye and I have laid out. First and foremost, you're going to have to make certain you've got everything other than fuel/air delivery right. Once you've reached that point, we can take a more reasoned approach to getting your engine running right.

[Bonzi Lon]

They have those hand held laser thermometers fairly cheap now. Works great in finding hot or cold spots all across the engine. Got my T&D set for $12 at Harbor Freight, paid for itself 3 times over first time I used it.

Bonzi Lon

[grantf]

In my opinion you should really check the fuel pressure. You can get a gauge pretty cheap, attach it after the fuel filter and use good hose clamps (ones for fuel injected auto's). Be careful when removing the hoses as they could still be under pressure and you do not want a face full of gas, don't ask my how I know this. My car used to run great until it was under load when it would sputter with little or no HP. The culprit was clogged fuel lines from a tank with rust in the bottom. It also made the fuel pump sound strained at times.

[Jennys280Z]

Hey guys, quick update here.

Regarding the buzzing sound I heard from the back of my car, I didn't even think of this until FastWoman nailed it, but that buzzing sound I heard is almost surely some bolts I left loose (hand tight) on the back of the car (the ones that secure the end rubber pieces on the car). Since when I took the bumper off, I thought it was only the shock absorbers that couldn't be removed without dropping the fuel tank. GRRR

I did gently move the AFM device while the engine was running. When I opened the flap (via the metal lever under the black cover) just a little bit for less than a second, the engine dipped and almost stalled. Then I slowly let it return to the position it wanted to stop at. It shakes around somewhat while the motor is running. I didn't want to push it the other way because I didn't want to break it. But if you guys think it's a good idea to lever it up rather than down (to cut off the air flow) I will do that as part of my troubleshooting later this week. Why would moving it the other way increase the engine speed?

I'm really mad that a mechanic put headers on this car without coating/painting the iron. Now I have yucky rusty headers attached to my engine and what's to say that this automotive cancer won't spread to other parts of the engine or car? Also my oil pan is rusty and I'm debating how to de-rust it effectively. I bought some high temperature paint at Autozone, but other than hurting my fingers using sandpaper I don't know of a better way to get the rust off the pan carefully.

Would you guys trust a NAPA brand thermostat for my car or should I get some other type or brand? The guy there tried to sell me one and a gasket. He says the part is good and that he has one on his truck, but what am I supposed to expect a NAPA salesman to say?

Thanks again for helping me everyone. FastWoman is like my hero though. Sorry boys

Fuel gauge and fitting shipped yesterday and are on the way yaaaay! I'll get some fuel hose and clamps along with a thermostat and gasket at NAPA if you guys think I can trust NAPA parts. But I *feel* better getting some kind of Japanese part, like a Tokico or whatnot.

[cozye]

If you moved the lever on the AFM in the correct direction to open the flap more and it started to die, you are definitely not running lean. I'm assuming that you tried this with a very small amount of movement, like 2mm maybe ? If so, that means that your car is probably running rich. Even when properly tuned, if you move the AFM flap just a little, it will still idle up some I believe before bogging down. IF it bogged down immediately I would think you are definitely not in a lean condition.

Can you pull a couple of plugs, take a pic, and post ?

If you are running rich, your thermostat or water temp sensor could be the cause of the problem.

Have you been able to verify if the temp gauge in the car is correct ?

[FastWoman]

All of what Cozye said!

Don't be afraid to tweak the AFM mechanism a bit with your finger. You won't break it or blow anything up. Also don't worry that you're altering air delivery to the engine. You're not (or not very much). As Cozye said, you've established that your engine isn't running lean (provided your movement was very small). So now try it in the other direction. By closing down the AFM mechanism just a bit, you'll be leaning your mixture. Does that make the engine run better? Also does it run better if you open up a vacuum leak somewhere (e.g. by pulling a vacuum hose)? All of this would mean you're running rich. Possible causes could be running too cool (i.e. bad thermostat), a bad temp sensor, too high fuel pressure, worn injectors, and/or a stuck (open) cold start valve and/or inoperative thermotime switch. If your engine is running super-rich, the latter two possibilities would seem all the more likely.

You'll be able to tell a lot by the plugs. However, in my experience, a very badly running engine will give you somewhat sooty plugs even if the cause is a lean mixture. It's only when all cylinders are hitting reliably that plugs can get that chalky, white, "lean" appearance.

Other issues:

Rust on headers -- Don't worry about any "cancerous" effects spreading to other engine parts. Also don't worry too much about the life of the headers. Most exhaust parts rust from the inside out, where condensation pools inside. The headers are not prone to moisture accumulation. The only issue will be appearance.

Rusty oil pan: Well, there's rust everywhere on these cars. I've never heard of an oil pan rusting through, though. It's never a bad idea to paint something, but first you have to get it quite clean. That's going to be hard to do with an oil pan attached to the bottom of the engine, mounted in the car. If you ever end up pulling the engine, definitely paint the pan then (as well as other engine parts). Otherwise I wouldn't worry about it if I were you. (For instance, I didn't try painting my rusty engine block when I had the manifolds off of my engine. I thought about it, but I didn't feel I could do a very good job of it without subjecting it to a chemical soup that might be hazardous to other parts of the engine bay. I just scrubbed it a bit, sprayed a bit of fogging oil, and left it.) I do all of my painting/de-rusting opportunistically. Whenever a part comes off, it doesn't go back on without being de-rusted and painted (and that makes it slow going).

FYI, you can do a lot to stop rust by wiping an area down with Ospho (available at your local hardware/paint store), letting it dry, and then following it up with fogging oil. (Obviously don't spray your headers with fogging oil!) You can also do some local rust proofing with a WWII era product called cosmoline (http://www.cosmolinedirect.com/). That stuff is on my "to do" list.

[Jennys280Z]

Awesome advice FastWoman/cozye Thank you!!!

OKay so I'm here for another update. I did a lot of testing today and have a lot of info here so I'll try to list it in a fairly schizo-less manner.

I pulled, cleaned and gapped all my plugs. They are NGK V-Power GR5 (projected, resistor, 5 heat range, 1mm gap from factory) plugs and I know everything about NGK plugs now as I've studied their entire product line and codes and know how to read the entire lineup. Anyhoo, my #1 spark plug gap was way too big. It was about 0.39" where the FSM wants gaps at 0.8mm - 0.9mm (0.032" = 0.036"). I made sure every plug is gapped right at .035". Interesting that I had that problem over the spring where my #1 plug wasn't firing and after running it a lot like that, I got a lot of gas in my oil. I wonder if the ignition wasn't strong enough for the plug to spark with a gap that big. I don't have any better-than-stock components in my ignition so I probably shouldn't get too fancy with my plugs either.

I got my fuel pressure gauge on right where cozye has his. I couldn't get the hose on the gauge so a few friends helped me with that part...but ummm...oh and my gauge had a drippy leak until I went back to the parts store to buy some teflon tape and a few winds of it on the male threads and the leak was gone! Fuel pressure right after starting the motor was 38psi. After it idled for a while and the RPM came up, fuel pressure was steady at 36psi. My fingers hurt! That was a bigger job than I thought it was going to be. I had a huge list of all this stuff I wanted to do today on my day off but it'll have to wait till the weekend but the weather is going to be crummy so i dunno. But I'm glad that my fuel pressure is in line with what the FSM says I should have so that's not the problem.

The air temperature today was 38 degrees F.

I started the motor and it fired right up again on accident. (I was just trying to blip the key to increase fuel pressure through the gauge in stages to check for leaks safely). One thing that works great is starting my car. I had the digital tachometer attached to my battery and spark plug wire #1 the whole time for monitoring engine speed.

AFM test:

This was a bit surprising and counter to what I wrote here before and in-line with what I have been told to expect from you guys. I moved the AFM CCW about 2mm or 3mm and the RPM raised slightly, maybe from 800 to 830. I moved the AFM CW about 2-3mm and the RPM dipped down maybe from 800 to 700.

I sniffed for vacuum leaks in all the places I could think of with a can of carb/choke cleaner and couldn't notice anything at all.

I sprayed at the PCV hose, 16mm vac hoses, intake manifold gasket, idle speed screw, throttle body, AFM rubber boots, etc and couldn't notice any discernible effect on the idle at all. It was still warming up and still chuggy sounding, and varying +/-40RPM but I didn't notice any spikes greater than that to give me confidence I found a vacuum leak. To be adventurous and to see if I could hear a difference in the idle, I sprayed a little in my air intake and the RPMs noticeably dropped for a few seconds as the engine received the carb cleaner.

I think it's safe to say my car is getting all the fuel it needs. Maybe too much. It's weird how there's no black smoke. I do smell gasoline though. The smell always gets in the house and kitchen if I leave it idling in the garage(ewwww!) My tailpipe put out little puffs of white smoke as the engine warmed up that mostly went away after awhile. There was water spray on the garage floor behind the tailpipe. I suspected it might be gasoline at first but I smelled it and tasted it and it was pretty much just water.

When i first started the motor in 38 degree outside temp, the idle was terrible. It was idling at 530-550 RPM for the first minute, then over the course of the next 10 minutes, slowly rose. After 10 minutes of idling, RPMs were 700. After 15 minutes of idling, RPMs were 750. Only after about 25 minutes of idling was I seeing 800 RPM where it finally leveled off. (I had set the idle at 800 before shutting the motor off last time I ran the motor). Even after 25 minutes of idling and some brief revving, parts of the engine still felt cool. The radiator cap (and front of valve cover) was barely even warm to the touch.

After 35-40 minutes of idling, my temp gauge in my dash finally moved up to the 120degree line. After 50 minutes of idling, the temp was still on the 120 degree line. I must have let it idle for an hour, some light revving of the engine and during this final 10 minutes the engine seemed to be running better than it was in the video. The temp gauge in the car might have just started to move off the 120 line. But barely. So no more than 125 degrees at the most.

I shut down the motor, carefully opened the radiator cap and stuck a cooking thermometer in the coolant. It rose to 132 and no further. Just like the top speed of my car yaaay!

So based on this result I am going to conclude that the thermostat is bad and the gauge/sender (though reading a bit low) are okay.

I also managed to pry apart the bullet connector coming from the coolant temp sensor (it's where the green wire connects to the red wire) and some manuals say you should disconnect this and ground the red wire to set your dist timing. I had cleaned all the other bullet connectors earlier this year but this one from the coolant sensor was a real bugger and it was the only one that I couldn't pull apart because I wasn't strong enough. But this time I lifted and loosened the connector with a tiny screwdriver and then used some needle nosed pliers with my left hand and got it apart. It didn't look too dirty but it got a big dose of Deoxit anyway.

One of the bolts on my thermostat is rusty and I put a 12mm socket to both the bolts to see how tight they were. I could move the other one but this rusty one I dunno. I sprayed it good with some WD40 and I'll have to wait till the weekend to see that hopefully it's not seized up. NAPA is ordering an OE 180 deg thermostat for me that they'll have tomorrow morning I can pick up anytime.

I've noticed over the months that the colder it gets outside, my temp gauge in my dash keeps reading lower and lower. At 38 degrees outside it couldn't even manage to move off the leftmost line. I'm not that experienced so I'm not 100% sure that this is abnormal but I think that it is and this is showing a bad thermostat. It's like I can't warm my car up. And maybe running my motor for very brief periods and just at idle could have caused some other kinds of problems. I read a lot of Z owners who say stuff like the car doesn't run good until it warms up, or to take it out for a good drive on the highway to "blow it out" whatever "it" is.

Anyhoo luvvers you guys! Hope to hear back from you!

xx

PS the AFM works counterintuitively btw. When you close it, it runs leaner? I figured if you opened it, it would run leaner! It's all still very mysterious to me. That AFM. I've read a lot about it...including your "purs" thread Fastwoman, and a big article on adjusting it on AtlanticZ but I admit I didn't understand half of what I was reading

Edited December 2, 2010 by Jennys280Z

[FastWoman]

Jenny, your AFM test establishes that your engine is running too lean. (I think your shot of carb cleaner into the intake might have been too much.) When you open up the AFM flap, it signals the computer to deliver more fuel, which causes your engine to run faster. You can go ahead and move the flap further than 2-3 mm with your finger. Go ahead and move it as far as you need to, in order to achieve the fastest idle. When you keep moving it farther and farther open, you'll go past that peak point, and then the engine will start bogging (as the mixture gets too rich). That will give you a preview of how your engine will run with the proper adjustments and repairs.

(1) First thing is to replace the thermostat. Sometimes you can loosen a bolt by hitting it with a blow torch and then letting it cool back down. Be careful, though. You can also try tapping on it lightly with a hammer. Obviously be very careful not to ring off the frozen bolt. If that happens, though, your next step would be to use a blow torch and a pair of vice grips.

(2) Next is to establish that you don't have any remaining vacuum leaks. The very best way to do that, IMO, is to do a whole-intake test such as I've described. Remove the AFM, plug the rubber boot with a yogurt cup, and "inflate" the intake manifold by mouth through an intake fitting. If you find you have a leak that way, your next steps can be to track down where it is.

(3) After you've gotten your engine solid, then make sure all your sensors are within spec, per the EFI bible.

(4) Then after all that is done, you can richen your fuel/air mix as much as needed by inserting the potentiometer in series with the temp sender. This will compensate for drift in the calibration of the ECU that has probably occurred over the decades.

That's your four-step plan, to be taken in that order. Have courage with #1!

Peace,

Sarah

[Zed Head]

Hope I'm not butting in but I had a couple of suggestions.

Using a torch on the aluminum thermostat housing will help a lot in removing the stuck bolt. Aluminum expands quite a bit with heat. I just took a bunch of spare parts off a spare engine and several bolts would not budge until I hit them with a torch. Of course, you'll have to avoid burning wires, but even a short time heating will make a difference.

The other thing I see is that, even though early indications with the AFM flap are that you might be running lean, your fuel pressure reading is too high. If the regulator is working correctly it should never go over 36.3, and on a running engine,with the vacuum hose connected to the regulator, pressure should be at 30 psi or lower, depending on manifold vacuum. Maybe your vacuum hose to the regulator is split or disconnected? The 36.3 psi number in the FSM is for a non-running engine, fuel pressure with no vacuum in the manifold, or with the vacuum hose disconnected. You can test the pump and regulator alone, engine not running, by removing the small wire from your starter and turning the key to Start. This will run the pump without cranking the engine.

Just one more perspective...

[cozye]

I agree with Zed. My first though when I started reading your report is that you may have a faulty fuel pressure regulator. Try running the motor hot, then disconnecting the vacuum line like Zed said and see if fuel pressure rises. If it doesn't, the FPR is faulty which will cause your car to run a little rich. The only caveat here is that the cheap fuel pressure gauges are not always super accurate, so what you want to see is there is a difference between having vacuum on the FPR, and no vacuum. We know your vacuum is a bit low, so you might not end up at 30psi on the fuel pressure at idle, but it shouldn't be 36 regardless. When mine had low vacuum I was around 32. If you have a mighty vac, you can also connect the mighty vac to your FPR for test. Put 17hg of vacuum on it and observe change in fuel pressure. Also watch and make sure than the FPR holds that vacuum and doesn't leak down. The FPR is a common failure part.

Second, I think Sarah might be jumping the gun a little on thinking the car is running too lean. She might be right, and we both have had the problem she is refering too, but you need to get the other issues fixed first. Also, with the AFM flap movement, even when the motor is running right, it will idle up just a hair when you move the flap a tiny bit to make it richer. As far as understanding the direction of the flap, just know that the AFM tells the ECU to add more fuel based on the air flow into the intake, so the more the flap opens, the richer it will run.

Here is good info on the AFM

http://atlanticz.ca/zclub/techtips/afm/index.html

I would not attempt any adjustment of the AFM until you get the themostat fixed, and confirm 100% operation of your FPR.

[FastWoman]

Oh yes... Zed Head and Cozye are correct about the fuel pressure! I had misread and thought your reading was without the engine running (in which case it would be roughly normal). The fact remains, though, that richening the mix raises the idle. Fixing the fuel pressure problem will lean the mixture a little. It certainly needs to be done, though.

I think it's important, BTW, to go ahead and tweak the AFM with your finger to attempt to find the best/highest idle, preferably with a vacuum gauge attached. If it feels/sounds pretty good, and if you can pull a pretty good vacuum (ideally 18 or 19), I think you can rule out ignition problems and gross mechanical problems (e.g. valves).

Also I want to be clear: I don't think you should ordinarily adjust the AFM, either now or later. Quite the contrary, I think the best final solution is to fine-tune the coolant temp sensor circuit. But again, that's for later, not now.

One final note: I'm remembering how horrible one of my thermostat housing bolts was. The bolt was deteriorated and rung off. I also removed the thermostat housing from the side of the head, and the shorter bolt (towards the rear) rung off too. Fortunately the latter bolt could easily be removed with vice grips, as the jam was mostly in the unthreaded hole running through the thermostat housing. (I had to pry the thermostat housing off of the broken bolt.) The first rung-off bolt was the worst I had encountered anywhere on the car. I ultimately had to drill it and chip out the remains of the bolt, and even that was pretty hard. Sooooo... If yours is like mine was, there's no shame in taking it to a mechanic who has the tools to replace the thermostat.

Another note: After you get the thermostat housing apart, clean up the threads with a tap, and install a couple of threaded stainless steel studs (which you make by hack-sawing the heads off of a couple of SS bolts). Use nickel antisieze. Then secure the thermostat housing cover with a couple of stainless nuts, regular washers, and lock washers. You'll never have a difficult removal again. (That was Ztrain's excellent suggestion.)

Edited December 2, 2010 by FastWoman

[cozye]

oh yeah, I almost forgot to comment on the seized bolt too. Get some PB blaster and start soaking it daily. When you attempt to remove the bolt, use an box end wrench and keep working it back and forth gently, don't muscle it. Be patient. I think you can get it loose without breaking anything. I got all my exhaust manifold bolts off with this method without breaking any of them, and they were very rusty and deteriorated. Do not use WD-40, it's more of a cleaner and not a penetrating oil.