JDLHP

Hello every one!!! I am new to the forum and new to the foriegn cars. I am not new to working on cars I have worked on Mustangs for 30 years I just bought a 1985 300ZX turbo with 690000 miles on it. The body and interior are rough but the engine and trans appear to be good. I towed it home because it wasn't running the gas tank was out of it and the car had sat outside for 6 years. The previous owner told me it needed a fuel pump.
I installed a 255lph pump in it and put the tank back in. I was able to fire the engine but it wouldn't idle or run hardly at all. other parts that were replaced were the plugs, plug wires coil and IAC. I found receipts in the glove box for a Mass air flow sensor head temp sensor I also found a box of old parts in the car that had a fuel pressure regulator and an O2 sensor in it looks like the previous owner was fighting this problem for a while.

I started to trouble shoot and I found a couple of vacuum leaks and the EGR valve was leaking so I put on a new gasket. I cleaned and tested the EGR Valve and the solinod with a vacuum pump and they are fine. I finally got the car to stay running by disconnecting the IAC valve and I can get it to Idle a little over 500-600 rpm but it never goes to a high idle and it still takes 3-4 tries to get it to start.

Before I disconnected the IAC the computer was showing an Idle switch circuit open code with the IAC disconnected It is showing a bunch of other code but I dont think I can trust the codes when one part is disconnected.

when I give the car gas it coughs sputters back fires and wont accelerate if I tap the gas and gain rpm by repeatedly pushing the pedal I sometimes can gain RPM and over 3000 RPM it will rev and it sounds great but you cant hold RPM only rev.
I hope some one out there can help. If I cant get it to run I will end up parting it out

JDLHP

I am pulling my hair out over the problems I am having I bought a 1985 300ZX Turbo. It wasn't running when I got it. I have replaced the plugs plug wires tps fuel pump and filter. it will start after several tries idles around 500rpm and wont adjust wont run with (new) IAC valve pluged in. Back fires, runs rich wont accelerate. I have re timed it. Dont think the timing belt is bad but I dont know where to turn the cat is not open but not completly pluged either. Help Please!!!

Thanks

John

rsfire

I've been having a very similar issue for some time now. I've put a good deal of time and research into this issue. The biggest thing I heard to fix was the CHTS (Cylinder Head Temp Sensor). I replaced that among other things with no luck until I pulled the engine for a rebuild. I just finished it today and it still has the same problem sadly enough. Earlier if i let it idle till warming temp (15 mins) it would run fine. But now after it warmed up it was drivable but would still cut out badly. From 0-15% and 70-100% throttle the car would accelerate fine, but anywhere in-between it would sputter and backfire pretty badly.
So if anyone has any ideas what I can check let me know. And I'm going to be experimenting tomorrow so if I can figure anything out I'll post it on up.

84_300_ZX

This may sound stupid, but try checking your voltage at the battery when running. My car does the same thing (I have a terrible battery) when I first jump start it and remove the cables. If I leave the cables on the other battery until the Z starts charging decent, it runs fine.

86tcoupe

Welcome to very early On Board Diagnostics
fun aren't they ?
have you checked the red & green flashing lights on the ECU (I know old post) ?
These years you really need the break out box and thick manual on the vehicle to diagnose FI problems somewhat quickly

do the injectors all tic /sound the same using a stethascope as posible you have one irratic