MR2ZX

Hello Everyone! I've had my 83 280zx for over two years now, and I've always had a problem with the idle. After doing every easy changeout I can, I was hoping I could get some feedback on what y'all think needs to be fixed or tested more, since I'm stumped and don't want to go around replacing stuff needlessly.

When I first got the car, it would run hot and would stall if at idle for awhile. I replaced the radiator with an Aluminum 3core and changed the thermostat to a 160 and now the car runs cool (Never gets close to halfway). My car would still run rough at idle and stall though. I did a intake leak test and found that smoke was coming out of the EGR diaphragm and PVC hose, and replaced those. D:idn't really notice a change to how the car ran after doing that. After awhile I found out my fuel pressure regulator wasn't working correctly (pulled off the return hose while it was running and fuel wasn't coming out), so I replaced that. Car wouldn't stall at idle anymore, but I have never fully tested that because I don't like sitting at idle long; the car still idles rough.

So to give more detail on how it's running at idle, when I get to a traffic light, the car runs fine at first, at around 600RPMs (Automatic). After about 10 seconds, the idle will fluctuate a tad (~75RPMS max) and there's a very noticable bounce to the car. The temperature will also raise a little bit, but nothing extreme. I do have the 160 thermostat still in and it does not get anywhere close to half.

Also, if Im on a highway for a bit, then take a exit to go to a store or something and let the car sit for a bit, the heatsoak gets extreme. I assume it's pretty normal for that to happen, but what I find odd is that after trying to start it after it sits for around 10 minutes, the car has a very hard time starting. Most of the time I'll have to hold the throttle down a tad while turning it over, then still hold the throttle for about 30 seconds just to get it to not stall out. It runs very rough during that time, then after a minute it's back to normal.

Any suggestions? Thanks for taking the time to read. Here's a picture of her (The previous owner let her sit in the Texas sun way too much unfortunately).

FricFrac

The two main sensors are the CHTS and the AFM that cause issues like these. Get the FSM from XenonS130 and go through the testing for these guys.

The best solution for heat soak is to take the intake plenum off and put a thermal barrier on the bottom of the heat shield. Ceramic coated headers and/or wrapping the manifold or header helps as well.

zedsdeadbaby

Get rid of that thermostat. Your car isn't warming up to operating temp. Surefire way to always run rich and accelerate engine wear.

Have you tried raising your idle? Replaced all vacuum lines even if they look good? Cleaned all connectors under the hood and the ecu plugs? Try jiggling your injector harness. People, including myself have been finding old, weak, broken solders there recently.

MR2ZX

I had the regular 180 (Or 185?) one in two weeks ago. It still wouldn't get halfway, unless it was sitting at idle. Car still ran rough, and heat soak was to the point of taking minutes of getting the throttle position right to get the car started. Ill replace the thermostat back to stock if I can get the idle problem fixed.

I have tried raising the idle, but it will still fluctuate and run rough. I've replaced most vacuum lines. My injector connectors are terrible, and if I tug them a bit the car will run rough. The connectors are at the point where they'd have to be replaced, not repaired, for almost every connector in the bay. There's a very distinct difference though comparing the idle and the idle with an injector unplugged.

As for testing my AFM and CHTS, I've tested both and they seem fine. I would just go ahead and replace the cylinder head sensor, but when trying to remove it a long time ago the nut portion of it broke off and spins freely now. I'm not confident enough to take a drill to it and try to get the rest of it out, since atleast at this point the sensor readings seem close to normal. I've played with the spring tension of the AFM in the past and have it currently to where it sounds the best / highest RPMS.