Jennys280Z

He seems to have a good connection to engine rebuilder(s). Unless someone has info. that they're not good work? Anyhoo, the pictures of the L motors for sale on Ebay look good to me. I've read a horror story or two about this guy in past threads here and I wasn't sure how to interpret it. I see someone with a successful Ebay business. He might not be perfect but has many good customer reviews. "Life is too short for fussing and fighting my friend." We all like Z cars; where's the love? Let's all just get drunk and share the love with each other! Or else...who is the proven reputable (and affordable) L-block engine builder out there? And before you say "myself" or "I know a guy" how about someone/someplace that I can actually Google.

I'm too scared to do that, FastWoman. I barely trust myself just to install the thing and cross my fingers it works (or even that my car runs better than it does now and not worse). If you were here I would let you do it. But for posterity sake, I will consider taking it off and testing it properly (12V should probably be used for a benchmark) AFTER using it for over a year. But no, I don't want to install my CTS first which I could have done tonight. I got the CTS in my hand but I won't dare install it without the AFM at the same time.

Next to the valves, I almost forgot that I also want to tighten my cylinder head bolts once I get the rocker cover off. I suppose I should do that cold before my first cold valve adjust/check.

When you expose the mounting bolts after taking off the interior panel, you might run into quite a bit of epoxy used by the factory. Spray the bolts well with WD40 and save yourself some time. I also used a rubber mallet to "tap" the taillight assembly off without breaking anything. It slides straight off and straight back on. Don't fight the glue with a wrench or your arm strength, break the glue with WD40, don't break the part in your hands. Once the entire assembly is removed from the car, the taillights can be disassembled from the plastic plate, which you'll learn is a brown colored plastic that was painted black on the outside by the factory. The "chrome" trim can further be removed from the black facing as well. It's a good opportunity to clean what is normally one of the crappier looking areas of our cars. I had several hornet nests and near-handfuls of dirt back there so it's not just about the aesthetics.

I was out of the resistance range at 50degrees, yes. Until yesterday I was going to test the CTS at the ECU at 176degrees which would show me that it's botching the mix when the engine is hot too, but perhaps being out of spec at a single temperature is good enough, good enough to replace a $13 part. x Well to do the mechanical tests with the spring tension like I did with my AFMs here, I'll need inside that cover. Of course I'll do the electrical tests with the ohmmeter. If I don't get a 180/100 combo plan obviously I'm going to be distraught and will need morale support here from y'all Another thing that's been bothering me too is the thought of replacing the CTS without the AFM and leaving my AFM wheel where it is. I'm tempting a frontfire I just know it...women's intuition...something tells me to wait on the CTS until the AFM is here and install them both at the same time. All just a newbie going on nothing but theory and a hunch, as always. :classic:

Okay I just splurged on a new AFM and CTS. What kind of wrench is best to take off the CTS? I sprayed some Kroil on it a week ago anticipating taking it off to test it. It's been replaced once on my car in 35 years. I figure since it's only $16 including shipping I might as well slap it on at the same time as my new AFM.

Interesting idea! Is there an easier way to run parallel than with a 2nd CTS? Yes I don't know what my car's problem is yet with running rich. I'm considering walking the AFM wheel another half-tooth to full tooth richer than where I am now because I don't want to wind up too lean from fixing something and then risk backfiring out my intake, and I have a feeling that would make a better mixture compared to where I am now. Did you mean in your first paragraph that I should replace my CTS even if it's not out of spec? If that's what you meant then I'll just buy one and replace it. I looked at it and noticed how hard it is to get a wrench in there. Rut ro! It's all green too like an old copper statue in E.Europe.

Hehe I will send the blueprints to the machine shop tomorrow morning. That'd be the big daddy of all AFM tests if you could do that with a shop vac. Yup I definitely have two 1976 AFMs that are physically identical and have the exact same readings. GRRR

I'm skeered. I do have old boards of all kinds so that wouldn't be a problem. For adding resistance to my coolant temp sensing circuit, that is enriching the mixture I would think. My resistance at 50degF air temperature was a bit high (4500 ohms vs. 3250-4150). I hope that my reading at 180degF will be in line but it might be too high as well. Will such high results mean that I should replace my CTS and that is the likely culprit in funking up my mixture?

I live in the south which is one of the reasons why I'm not going to replace my AR. If I lived in New York or Ohio I would have swapped it out for a new one I'm just not going to drive my car in the cold anymore! That ought to take care of more than half of my AR problems right there. Yes it's winter right now, but it's going to be over 60degF here tomorrow and sunny. Perfect drivin' weather! xx

Can you come over and help me solder the resistors? I can scribble on a schematic. I would need your help to actually DO anything! R10 looks easy enough to do (in theory) but what about the desired resistance value of R0? I just wonder about the point that Zed made, if this shift of 25% (which Zed noted a range is also increased about 25%) reshaped my mixture curve at all? If it didn't and my curve is parallel to the original curve, then the adjustment at the wheel should move me over to the point I should be and result in a 100% fix. Good advice on the CSV! Thank you so much! Despite the promising look to the pictures...I have a feeling this isn't going to be much of a fix. It seems like my valve closes too quickly/easily. Just from the heat of my hand holding the part while cleaning it? I knew I was hot but not that hot Just based on tinkering with the AR, it seems like I can get it to open like that after manipulating it with a screwdriver, but when it starts to close from handling/cleaning it didn't seem to reopen all the way till the screwdriver...anyway it was worth a shot. I did shake particles of grime out of it, FWIW. I wonder if I'll see above 1000RPM at least the first time I start the car...will know hopefully tomorrow. LY guys

Doubtful Zed. I never had a high idle problem that I had to dial down with idle adjustment. My car idles @800RPM for 30 seconds then drops to 550-600. It does this every time, so the symptoms are that it opens and closes consistently it just doesn't open enough. It will heat up and close eventually with the heat of the engine, and it does close as i tested with heat rather than voltage. As for the voltage heating the heater and closing it, I'm considering the possibility my car will behave better with the thing unplugged, as it would heat up slower and give me at least the 800RPM i start with for a little bit longer. I'm thinking now that I can get it to "stay" open more by moving it with a screwdriver, but just handling it and warming it up with my body heat it seems to close it up again like the first photo, and then it doesn't open up any more than that until I prod it with the screwdriver again. So I suspect that I'll install this same AR and it'll work better than before but only the first time I start the motor and heat the thing. That is, when it cools again it won't open up that much on its own. So I guess in that, it isn't opening consistently, but it closes just fine. I'll have it installed again this weekend...see if there's any improvement which I doubt. Then I'll flip a coin whether I want to buy another one. Will test the CTS (hot) and CSV from the ECU too and see if there's anything untoward going on there. The local mechanic here who's worked on Zs for over 30 years said he's never replaced a single AFM in his career and told me I'd be wasting my money on a new one. I admitted that my car might run a lot worse with a rebuilt AFM installed and he's almost talked me out of replacing it....sigh so i dunno. Once I get the rear end reassembled and legal again I'll make the 30 mile drive out to see him if I can't diagnose the problem myself and that 60 miles will be the first real drive in a long time. I just hope I don't get stranded or something.

Cleaning the air regulator, I've sloshed, soaked and spanked this AR with WD40 for 24 hours and am trying to determine if I got it to open any more. Maybe it appears that I have but I might be kidding myself. A local Z mechanic suggested I try the soaking bit because as he said these things get gummed up with residue over the years. I shook the AR in an arc a few hundred times till most of the WD40 came out, and little pieces of dirt or whatever were coming out in the liquid the first time. Another soaking overnight got me to this point.... xx

I'm not going to be mean to anyone because that would be mean. But on his site he says his car runs on Microsoft. Interpreting that, I think his car is virtual. A PC game for imaginative young mechanics perhaps?

Wow you're like an electrical engineer AND a chemist!

Looking at the circuit design, it looks to me like my R0 is toast, and that is fixed, and independent of the potentiometer wipe, as verified by my unchanging values I tested. My 8-6 reads too high as well, but I suspect R10 is the culprit there. I don't see there needing to be anything wrong with the variable resistance from 7, other than the ends are wrong. I don't think there's anything wrong with added resistance in the pot, I think that it's possible that R0 and R10 have knocked themselves up ~+25% for whatever reason. I did see a smooth increase in resistance as I moved the wiper across the trace (on either side of 7). I supposed that was validation enough that the potentiometer is fine in that regard. Both AFMs I tested (actually this almost doubles the number of test results in that I fully tested two AFMs after pulling mine out). From the design, yes they're obviously in series, and I'm sure my total between 6 and 9 would be higher than Anthony's and Zed's. I'll be 352 Ohms while, I should be expecting 280-290 Ohms.

Hmmm based on that, our driveability symptoms are quite different despite our identical readings at the AFM. Here I am adjusting my AFM 5-teeth lean for a noticeable improvement and not getting any backfires at all. I noticed no gassy smell, no smoke out the tailpipe either. With the way yours was running with your AFM though, it sounds like the last thing you would have wanted to do is adjust yours leaner when you're backfiring out your intake. And my car is definitely running a lot better than the way you're describing yours. It just adds to the mystery here. The more information we share the more questions I have. I still have to believe I have a rich running condition that I'm compensating for by leaning out the mix through the AFM, either because of the AFM itself, or something else. Like the coolant temp sensor, leaky cold start injector. The FSM says the CSV should kick in for 8 seconds and then it's done with its business, unless there's a problem with it, and it's failing/leaking. If it's failing I would presume it wouldn't add fuel for as long as it should, if it's leaking maybe it adds fuel incessantly? My car starts well enough. Fuel injection...gotta love it. Even when I'm having air/fuel issues, I still love it. It's been said my fuel pressure is a bit high, the car starts fast every time but I'm not holding pressure in my rails for much more than an hour. Dunno...maybe my FPR could also be contributing to a rich problem. Some guy on youtube said that a Nissan mechanic told him that if he tapped on his FPR enough the pressure would build up to like 40-something psi. Sounds like a terrible idea to me, but he was running a 280ZX turbo so maybe the rules change in that case.

So you were probably running lean and you started doing good stuff in good order to tune the car, and wound up running rich...until you replaced your AFM? Is that correct? AFR? You mean the air regulator? Your AFM is in line with the Bible. When the Bible says "approximately" it means within 5 or 6 ohms, so it would seem from the numbers...

I'm not going to challenge that you know your Ohms and I know what you're talking about. I'm not going to challenge your theory here or your superior knowledge. As for my limited background, we studied circuits in our 2nd semester Physics and I've had an undergrad electrical engineering class. What I'm questioning is, whether you're summing the numbers up right. I know you looked at the circuits...what I'm wondering here is if some of these values are only point resistances and so a few of the values are summed differently, or if we simply don't have enough numbers to do a proper circuit analysis. I know you've looked at the schematic so you have me at a huge disadvantage here But I see relationships here that add up very readily, like 126 + 73 = 199, exactamundo there, so says the ohmmeter. But presuming I measured 126 wrong would throw that value off. But I've really tested every value of this thing at least six times, not three. Because I tested my AFM from the ECU three times last year, and at least three more times with the AFM removed. I know how to apply the probes, and apply #2 pencil pressure, and see the ohmage decrease at increasingly slower rates until it arrives at the correct value et al Anyhoo, I still have to trust my bare hands and eyeballs more than your circuit analysis. Perhaps that it doesn't add up is indicative of it's failure? I sauced the carbon sweep with contact cleaner at least three times. I didn't rub it or put any friction on it. The potentiometer looked immaculate when I saw it the first time and still does.

Looking at the lower value and the upper value as two static points the shift does seem to be the same. I punched that through a calculator myself when I tested at the ECU (old thread) and saw that equivalency. I think the question is whether the entire curve is skewed exactly the same (25% increase across all points on the curve). I think this is unlikely because you noticed a difference at part-throttle but not at idle or WOT, and I would probably describe this to be the case with my car right now as well. Though leaning out the mixture even more than I already was has certainly made a difference for the better, I still notice something amiss at part throttle. Of course my idle is a disaster too but like cozye said, I think that's a separate issue however I won't rule out the AFM as possibly causing it. I wanted to ask you if you remember anything that might have told you that you were running too rich before you replaced your AFM. I know about the part-throttle symptoms, but did you have any rich symptoms that you can remember?

AnthonyG's numbers don't add up either (see post #201) and I'll just say I'm positive I didn't measure it wrong. In fact I measured all of these values three times at three different times and got the same results every time. Using the probes works the same for every test so it would seem unlikely that I messed up the same one three times in a row. Resistance across the probes was zero or very nearly so. My multimeter was almost brand new at the time. The 200 and the 75 figures change with the adjustment of the wheel. The 126 and 226 figures do not. I moved my wheel two teeth (~2.5) richer after cleaning and testing the AFM, and that 199 jumped to 206. The 73 increased 7 ohms to 80.

Yup I thought they could order one in 4 days but when I tried to order it, it was a dead link. Yup I know the AR won't help my car's running issues. If it was warm all year here I would put the old one back on and forget it. The way it is I dunno if I want to buy a new one or not. I took a picture of the valve fully open though. I hope this looks familiar. It looks like less than 1/3 to me but I will post a pic to see what you think. On 2nd look, it is definitely open more than 25% of the way...probably 29-30% if I had to guesstimate.

Well I have my air regulator off at the moment and have been cleaning it and testing it, and you're telling MY story...everything I just noticed is how you said it. The plate isn't opening up enough when cold. It's not 1/3 of the way open like the FSM shows. More like 1/5 of the way open, if that. I've tried to clean it with carb cleaner and WD40. Mine closes fully when hot, which I tested just by running hot water over the case outside the heater. It sounds like based on your results, replacing mine doesn't sound like a bad idea. I guess I could clean it, heat it and let it cool one more time to see if I see anything opening up any better, but if not, then maybe I should replace it. Having a good AR could make warmup problems a thing of the past. I took a look at the curves for the AR in the FSM. It's no longer functioning at all after 8 minutes or 180deg whichever comes first and it's a linear curve all the way down either way. But then I wonder what your car was idling at cold before you replaced yours. Probably not the 550RPM that mine drops to. I get about 800RPM for about 25 seconds and then a big drop to 550RPM. If the AR is not responsible for this sudden drop, then presuming I'll get 1300RPM from a new AR, I'd only drop to about 1050RPM due to whatever is causing my idle bog, which is still very healthy compared to what I've had. But since it's not opening up all the way, I supppose this is the actual reason why I'm only getting 800. Why it only lasts for 30 seconds or less, I don't know. Maybe this would also be a symptom of the same weak spring. It looks like I can take this thing apart btw. A glue blob keeping me away from a screw that keeps both halves of the casing together from the looks of it. Of course it's probably pressed or sealed with a lip or whatever but still, I've been tempted As for the AFM if you test a 126/226 that's the only way at this point I won't send it in for replacement. So if you can still test yours this weekend let me know! I want to replace it since this is almost surely a case of Garbage-In Garbage-Out (ohmage to the ECU). I'll be driving a car with what I have to assume is a less-than ideal-shaped mixture curve and while I've "compensated for it", maybe I'll never be running 100% better until I do this. I'm trying to reconcile how my car runs with Zed's who said he had part-throttle issues when his AFM read like this. I suppose that could now be the case with my car as well, thinking back at how it drove on the road. I wondered theoretically if it's possible my car could run better at WOT now than with a new AFM...but I have to trust the folks at Nissan would have known how to set this thing ideally already.

Hey guys! Cozye: On the ECU it's pin 6 to pin 8, 8 to 9, 7 to 8, and 6 to 7. But especially 6-8 and 8-9. I noticed that as I adjusted the wheel CCW, the numbers of the last two readouts increased ~2.5 ohms per "tooth" of adjustment while the first two stayed exactly the same (226 and 126). I'll hold off on everything till the weekend and yup, I was thinking of checking the temp sensor after my car is fully warmed up since it's really a range reading and I can't tell as much with only one shoddy data point. Zed: I was thinking the same thing earlier. I really don't want to pay $100 for this dumb thing and I was thinking earlier of just pulling it off and trying to clean it. I think there might be a decent chance I can fix it doing this, or at least get its performance better than what it is. I didn't know what the valve would look like or how much access to clean it I'd really have (I even thought of submerging it in WD40 for a few days if anything else). I suspect my idle issue is separate from the way the car runs on the road however with this AFM the way it is, I don't know. I start the motor cold and it idles at around 800 for about 20-25 seconds and then it bogs down to 550RPM. Not slowly in stages but all at once. And warming up takes a lot longer at 550 than at 1300...although I can remember the bad thermostat days *shudders* Yes it's closing when the engine warms up but it's only opening for 20-25 seconds and probably not as much as it should, if I can lay blame on this thing for at least my idle issues.

If nobody can post a 126/226 I'm going to buy a replacement AFM. Looking back on an old thread, I already tested the Air Regulator and the coolant temp sensor twice from the ECU. On the Air Regulator, I should have gotten "Continuity" where I got 68.7 Ohms. (EFI Bible, Test 1-8, p. 56, Pin 34 to Ground). I asked on the old thread and never got answered so I'll ask again here. Is 68.7 Ohms "Continuity" or am I looking for something like 0 or 1 or 2 Ohms here? I tested the water temp sensor at 50degF air temperature, and got 4290 Ohms where I should have expected 3250 - 4150 Ohms (at 50degF coolant temp). Maybe it was a little less than 50F outside, and so this result is inconclusive. (EFI Bible, Test 1-6, p. 54, Pin 13 to ground). If I'm going to blow $700 with the test results I have already, I might as well slap on a $20 coolant temp sensor and make it $720. Looking at my repair records, my temp sensor has gone out once, and my air regulator is original.