DuoWing

Ok, here's a question for you Z31 owners. Have any of you messed with or had to adjust you idle mixture ratio via the adjustment screw on the MAF? I'm trying to get my idle just right, and when I check my idle mixture as per the FSM states. Warm up the car, make sure diagnostic selector on ECU is fully counterclockwise, turn off car unplug TPS, turn car back on, make sure O2 is functioning and check the two LEDs on the ECU. It says the lights should be blinking simultaneously if your idle mixture is correct. Now does this mean that the red and green lights should be going on and off at exactly the same time, or does it just mean that you're good as long as both lights just happen to be blinking?

there's a good chance that the rear most exhaust stud near the firewall has broken off. This is fairly common on these cars and will cause an exhaust manifold leak. My 83 ZXT had this issue, while cold it was a good bit louder and the turbo sounded like it was screaming until the car would warm up.

If anything it almost sounds like the older pre-O2 EFI that came with L28s is better suited for tuning. Mainly because it's so primitive and doesn't have an O2 sensor that will at some point interfere and try to correct your ratio. You can mess with everything a little more freely.

I forgot about that. On my Z I have random issues were at times the Z because almost undriveable. It would idle poorly and then giving the car throttle it would bog down, start lean popping, and want to stall. My A/F gauge wasn't bouncing around indicating that the ECU wasn't balancing the mixture out. The first time this happened, I left the car alone. The next day it ran fine. It happened again eventually on my way home, eventually it got slightly better, but once I made it home the idle started to get real bad. Finally I just grabbed the ECU wiring and shook it some. Instantly everything smoothed out and went back to normal.

well I don't think the risk of fire is any higher, than if your injectors start leaking, or a fuel line cracks and starts spraying fuel on the manifold.

I would say hold off on the Air Flow Meter, until you're positive that it's the AFM. I was having issues with my Z at one point and I thought it was the Air Flow Meter, I had two of them and it made very little difference. When trying to diagnose the problem that knocking on the AFM's cover would cause differences in the idle. In the end it turned out the ignition module/temp sensor had gone bad. How does the car run while cold vs. warm? Also as people are saying clean up the connections to your water temp sensor, or at the very least unplug and then plug them back in a few times to help remove corrosion or possibly seat the connection better.

Depending on what year your Z is there's different things you can get rid of, but for the most part you can remove just about everything. For example on my Turbo Z I've removed the IACV/AAC, EGR, VCM, and VCV. You can remove the charcoal canister, but if you do that will leave your car smelling very gassy.

Definitely check your timing. On my turbo when I tightened up the dizzy after setting the timing, I had accidentally knocked the timing back a degree or two from 20. This was noticeably slower on take off, under boost, it even felt longer for boost to kick on. I upped my timing from about 18-19 which I accidentally set it at to 24 before TDC and that made a huge difference. Also depending on the year, check your O2 sensor. I remember when my O2 sensor didn't work the car's lower end response was really dull. It seemed really slow to respond until I hit around 2000-closer to 2500 RPM then it would start to go better. Finally when driving wiggle the wiring to the ECU, there's been a lot of cases with this old wiring being corroded, and I've had problems where my car would be slow to respond, sputter, hesitate, pop. Then I shook the wiring coming out of the ECU and the car suddenly jumped alive.

Ok, so recently I've been noticing that my Z's idiot lights, brake, door, fuel, etc are staying on. While driving. My ignition or charging light, or whatever it says doesn't work as the bulb is dead and I haven't pulled the cluster to replace it. Anyway for the most part my lights will stay on, sometimes they'll go off after a moment or so, or they'll stay on for half the drive home. Sometimes all the way until I get home. Today I turned the car off and it wouldn't restart. Battery had about 11.6volts across the terminals. Got a jump and made sure everything was off, headlights, interior lights, etc. Battery was showing about 13.8-ish volts across the terminals. My Uncle was saying that's normal and that means the alternator is working fine, that it may be related to a ground or some kind of electrical problem causing a short. One thing I've noticed for a good while is that my dash blower motor will randomly cut off and start working again while driving. The blower issue has been going on for a while, but just recently did this problem with the idiot lights start. After the drive back home with headlights on, headunit and speakers going, fan motor going, interior lights on, etc. I checked my voltage across my terminals and it was getting just about 13 volts. So this seems like the alternator is good. Turned the blower off and then I was getting about 13.25 volts, and the idle then started to smooth out. Would the fan motor shorting or arcing be enough to cause issues like this?

Lately my car has been having a sort of issue. My idiot lights ie: Fuel, Door, Brake, stay on when I start the car and while I'm driving. This is something that just recently started. I checked my belt and found that it was a little loose, tightened it up and the problem seemed ok, but I guess it wasn't the problem. Tonight on my way back from a friend's place, eventually my dash lights eventually got dim, my radio would no longer work and my fan motor stopped working. My headlights got really dim and everything. After a little while everything just suddenly lit up bright, the idiot lights went off, and my headunit and blower motor were working again. This seems like a symptom of a crappy alternator to me, I'll have to go get it tested. Can auto parts stores test your alternator in the car?

When you try to tighten further the nut slips, right?

I was missing two of these washers, so I made sure to use the ones I had remaining to be shared with the intake/exhaust manifold studs, then I had a bunch of thick washers that were very similar that came off of my 300ZX. I just doubled these up for the two outside studs.

Here's a few things you need to check. Check the Air Regulator to make sure it's closed all the way when warmed up and not leaking air. I've purchased newer air regulators, 2 now that have both been faulty and leak when closed. Also I don't know if it's a Turbo or N/A, but I've read many people having problems with the N/A BCDD going bad and causing idle issues. As far as a Turbo goes I used to have bizarre idle problems until I found out that I didn't even have the VCM vacuum lines routed correctly. Later I found out that my AAC valve although worked, it was going bad that when shut it would still allow air through putting the idle up higher than it should be.

I could be wrong on the 240sx throttle body, although I believe the Z31 might work, but you'd still need the spacer. The turbos never had an idle adjustment screw on the throttle body. I guess Nissan figured the newer ECCS, VCM, and AAC would be good enough to not need to adjust the idle? When they got to the Z31 they must have realized that sometimes it doesn't always work as it's supposed to and gave the idle adjustment screw back.

I'd like to do a throttle body upgrade simply so I can adjust the idle with an idle bypass screw rather than having to mess with the stock 280ZXT throttle stop. I've removed the AAC, VCV, EGR, etc so now I need to actually adjust my idle and that would make it a little easier.

Well being a turbo car it doesn't have the cold start valve or thermotime switches, and if the idle air bypass you're referring to is the air regulator I've put my ball valve in place of it so I can completely close it off as it was leaking when closed. One thing I may need to do is unplug the O2 sensor once the car is completely warmed up and see if the car still runs ok or goes back to bad hesitation. Oddly enough with the Cylinder Head Temp Sensor, the thing has been replaced a couple times. The previous owner had replaced it with a new one which turned out to be bad, I then swapped a CHTS from a Z that ran well and that CHTS soon turned out to be bad, it wasn't until I bought another one straight from Nissan that I got one that worked correctly. Although I'll have to test it as per the FSM.

Well I've been trying to solve this problem for a while now with no luck. I have a 1983 280ZXT Auto that's running an 84' 300ZXT ECU and MAF setup. Anyway here's my issue. When going from a cold start my car will start right up, idle decently, run well and everything. After a short period of time maybe a minute or two of driving, when I come to a stop my idle tends to get kinda rough, and I have hesitation/stumbling on acceleration. The car will start to go but not without stumbling. Then as I'm cruising along the O2 sensor will kick on and I'll pretty much have no issues, except for a little bit of a rough idle, but the car will run fairly well, accelerate fine and so forth. At full throttle or higher throttle my A/F gauge displays about 2-3 bars rich which I hear is normal for the turbo Zs and runs fine. The other problem that I have is generally after I get to a destination and stop the car, when I come back usually after 15+ minutes or so. The car won't be completely cooled down and I'll go back to having a whole lot of hesitation until the O2 sensor comes back on then the car goes back to normal. I've checked for vacuum leaks many many times by spraying brakleen everywhere under the hood with the car running. Ignition timing is just about spot on at 20 before TDC, etc. I just recently blocked off the AAC valve, removed the VCV, found my air regulator to not be sealing when closed and replaced it with a home depot ball valve to allow for testing. My idle now sits alot lower at about 500 RPM and the car starts to get a bit goofy so I need to adjust my idle via the throttle stop to bring it up a bit. This has been a problem that has been plaguing me for a while now, with no luck in solving it. So I'm hoping you guys could point me in some sort of direction.

Thanks for the info. I'll have to give that a try. I was also thinking when I do an oil change, I'll have to try running some ATF or Seafoam in the oil as I hear that works well for cleaning out the lifters and what not.

Alright on my 83 280ZXT with P90a head, I've noticed that sometimes when the weather is really cold, on startup my car will have a ticking for a second or two, then go away. The engine has a little over 93k miles on it. When it's warmer out I don't even notice this, and sometimes the car will tick for like a split second before going away. I mean this probably isn't a good thing, but I don't know if this indicates possibly a bad oil pump, or if it just has to do with an older engine and extra cold weather? I noticed that while driving my car's oil pressure gauge was not even registering, so I went and pulled off the oil filler cap from the valve cover, and oil was spitting up and out. So that told me I had pressure. I've ordered a new sending unit.

This is a great write up, oddly enough I've been pondering the thoughts of a BMW engine in a Z. As my friend recently got a 97 328is, I got to thinking, 2.8l inline-6 newer engine management, similar power, it just might be a good swap for the Zs.

As far as I know, the transmission doesn't matter when it comes to the ECU. I don't really know why it would anyway.

I wonder if your fuel pump is on it's way out. You said that the car ran fine at first? Just because the fuel pump is coming on doesn't mean it's good. I've heard that usually the fuel pump has more problems when warm, so it could be that after sitting for a couple of minutes or so it cools down a little. I'd say get a vacuum gauge, and a fuel pressure gauge. Check your vacuum to see if you have leaks that'll tell you something as far as if your pulling air in or not. Then keep the car idling with the fuel pressure gauge hooked up. Watch and see if pressure starts to drop after the car has warmed up.

This is a really weird method I came up with. One time when I needed a lot of torque on something and I just couldn't manage to do it, assuming the wrench and breaker bar is in the right position, get the wrench or breaker bar and if you can get it to push in the right position set it on top of a floor jack. I figure this thing can lift a car with no problem, so obviously it should be able to put more than enough torque on a wrench, and sure enough it was able to break the bolt free.

From what I know, is all you need to do is grab the analog gauge cluster from a 280ZX that has it, and grab that section of the wiring harness. I've never done the swap myself, but I hear it's pretty easy.

Hi, I'm still new around here, but I've owned a few Zs by now. I also have this thread over on Zdriver, but I figured I'd see if any of you guys could provide some assistance as well. Anyway I have this really odd issue that I can't seem to get rid of on my 83' ZXT. Anyway when the car starts up cold it doesn't drive well at all, I get alot of sputtering, popping, etc. Once the car warms up it pretty much runs fine. I've been changing, replacing, and testing things for a while now and still have come to no fix. Anyway I got done replacing my Intake/Exhaust manifold gasket last nigh and first off, when trying to get the intake to seat correctly I think I scraped up or took a little off the intake side of the gasket, not to the point where it was through but looked like it got scraped up, will this be enough to cause an issue? Anyway I got the car back together and threw my battery back in, checked everything, and fired her up. She fired up super fast. Was idling pretty high at first, but the car hadn't been run in a few months. Anyway I get into the street and try to go, popping, sputtering, etc. Just like it always does. If I hold the throttle steady eventually it seems like it picks up and starts to go eventually, then I'll let go and try again and then I'll get the popping/sputtering. Eventually when the car gets to about that first line on the temp gauge it all of a sudden starts running fine. Anyway I took the car for a drive, and next thing I know I see smoke coming from the hood. I pull over turn the car off. I had hooked up my temp gauge incorrectly so it wasn't working. Anyway you could feel alot of heat coming out of the engine bay and the level in the overflow resevoir hadn't changed. We let it cool for about 10 minutes or so, then I just decided I had to drive it back because I had no way to get back. Only a few minute drive anyway. So I'm getting back on the freeway and for a few moments there it starts doing the popping/sputtering that it only ever seems to do while cold. It goes away pretty quickly, I get back home, shut the car off ASAP, and pop the hood. Engine bay still feels hot, but there's no more smoke. I think it was just burning off the coolant I had spilled while filling the radiator. The overflow bottle's level had gone down, which to me meant it was pulling coolant through. My guess is maybe the thermostat got stuck? I also got my temp gauge hooked up real fast and it was showing just after about 3 minutes of the car being off, about normal operating temp. Anyway I'm kind of at a standstill as what to do now. I really want to get this car running correctly. I figure today I'm going to re-check/set the timing, do a compression test to see if anything happened from the heat, and try and test my CHTS. My thoughts are maybe it's the CHTS, the first time I swapped it from my 2+2 the car started up the next morning and ran fine, maybe just a slight pop or two, but no real hesitation. Then later after the car had cooled down it ran like crap. The car sat for about a week. I put in my remanned AFM and then the car ran really good. I was at a friend's for about an hour, came out and the car ran fine. Next morning car ran like crap again. I really don't know now what to do. Any suggestions from any of you guys would be greatly appreciated. So far I've done: New/Remanned Parts ---------------------------- - Battery - Battery Clips - AFM - Air Regulator - O2 Sensor - Injectors - Fuel Pressure Regulator - Ignition Control Unit - Ignition Coil - Distributor - Distributor Cap - Distributor Rotor - Spark Plug/Coil Wires - Spark Plugs - Intake/Exhaust Gasket - Turbo Downpipe Gasket - Turbo Inlet/Outlet Gasket - Thermostat Housing Gasket - Various Vacuum Lines - Hatchback Lift Supports Swapped From 83' 280ZX 2+2 ---------------------------- - TPS - CHTS Other ---------------------------- - Reset Ignition Timing with TPS connected - Re-calibrated TPS with feeler gauge - Plugged off EGR System - Flushed Cooling System Edit: Also what's a good method for checking for vacuum leaks? I've heard about the taking off the oil filler cap, but will spraying brake parts cleaner also help to find a leak? When I started the car up last night I was spraying brake parts cleaner along where the intake meets the head, near the afm, and stuff and didn't notice any idle changes. Although I don't know if the fact that it's high idling because of a cold start would make it harder to find leaks or not? Update: Ok I was outside messing with it, I was spraying carb cleaner everywhere under the hood pretty much and I wasn't finding the car's idle jumping or anything. I took the oil filler cap off and then the idle dropped, the car wasn't sputtering, and the idle didn't drop alot, but it was enough to notice a difference, and then I put the cap back on and then you'd hear the engine speed raise, so I don't know if I could still have a vacuum leak, or if maybe it's just related to a sensor? After a few moments when the car kind of slowed down and stopped fast idling a little, I pulled off the oil filler cap and then the car did start idling pretty awful, and jumped right back up as soon as the cap went back on.