Idle and running issues...

[TheRex]

Greetings to all.

I recently acquired a well maintained and slightly modified Z32 and unfortunately have a problem - 1989 swb manual Jap import.

It started to play up on cold start and would not idle unless you feathered the throttle, but once at running temp was fine. I tried another cold start valve which made no difference and now the problem has got worse - it is misfiring all the time unless heavily under load. Get it above 4000rpm however and it pulls as it should. It smells extremely rich.

Other than the cold start valve I've changed the obvious - plugs, fuel filter etc. The MIL is not lit and despite having the cable my Delphi diagnostics will not talk to it.

Any of you out there got any ideas? Thanks in advance...

[z.Leinbach]

Have you tried the cleaning the MAF and adjusting the IACV?? Might be a PTU issue?

[nissanfreak12]

Which PTU do you have older or newer version? Newer will be all black and older will be silver fins on the face.

[TheRex]

Hi thanks for the replies can you explain the jargon please for Europeans??

PTU is what? IACV??

Airflow meter is clean.

[90z32na.plumber]

Idle Air Control Valve is located on the rear driver side of the engine.

Power Transistor Unit is mounted on the front passenger side of the engine. The original PTU (metal with fins) was recalled. The new unit is black plastic, and has sometimes been relocated next to the air box after replacement.

If not the IACV or PTU, check your fuel injector harnesses and coil pack harnesses to make sure they are clean, tight, and not corroded.

[TheRex]

Thanks.

Cold start valve already changed and the PTU changed by previous owner. Ditto for injector loom etc.

Still running like a turd.

[nissanfreak12]

Maybe because its in europe? Lol, I kid.

On a serious note, check for boost leaks/Vac leaks. That will make it run like crap

Test your injectors, they should be between 10-14 ohms. 9.8 is bad and so is 14.2, get the idea?

Check the ECU for codes, dont rely on just the check engine light is on, actually go through the ecu to se if there is any codes.

[TheRex]

Hey I wish it was in Colorado. I wish I was to be fair, anywhere away from the evil and ever greedy French tax man

I've checked all the vac pipes under pressure there's no leaks. I'm going to test the injectors as you say and figure out how to get the ECU to speak to me. It's definitely over-fuelling but runs as it should past 4000 rpm. Are CO2 sensors a regular issue on these?

I'll update thanks for replying.

[nissanfreak12]

The O2 sensors only work after 2k rpms. You can test the sensor in mode 2, that will tell if they are turning on and off. Its an easy test, all is described in "everything you need to know...."

The coolant temp sensor also tells the ECU how much fuel. The CTS tells the ecu how cold or hot it is, when it thinks its cold, it will dump more fuel, hot is less fuel. But if it gets too hot, it will idle up in an attempt to cool the engine down.

Have you checked the ECU for codes? Physically go in and test, don't rely on the check engine light.

[nissanfreak12]

You know I read, your post but it didnt register.

Reading the ecu is simple, pull back the passenger carpet and the board(held on by 10mm bolts). Under that will be the ECU. On the side of it you will see a flat head screw piece in it. Turn the car to on, but dont start, go to the ecu turn that knob all the way over(I think clockwise), then all the way back. The check engine light will start flashing. It will do long/slow flashes then short/fast flashes.

Example; 2 long then 3 short flashes is 23. Long flashes is the first number and short flashes are the second number. Write down all numbers. if it repeats the same code, that means it is all done or that is all the codes it has.

HOw to reset, turn it back clockwise then counter clockwise.

[TheRex]

Thanks you explained that better than my Delphi although I had to purchase the adapter to OBD II before it decided to tell me there would be no dialogue!

The temperature sensor was one of the first things I changed. The battery is on charge I'll report back, thanks again for your replies.

[dzap]

Thanks you explained that better than my Delphi although I had to purchase the adapter to OBD II before it decided to tell me there would be no dialogue!

The temperature sensor was one of the first things I changed. The battery is on charge I'll report back, thanks again for your replies.

Was this ever resolved?

[TheRex]

Hi all,

Issue still NOT resolved - their are no codes other than 55 in the memory which I believe means all clear?

I just spent a few hours checking all the vac pipes one was split and now the turbo gauge works again but she is still missing, running extra rich and refusing to idle.

I'd appreciate any help does anyone have any thoughts? Many thanks

[TheRex]

Also Nissanfreak if you're out there - will I be able to test the o2 sensors ? I can no longer get her to running temperature so will the test work? Ditto for the cold start.

Also, how can I test the PTU?

Thanks and sorry for all the questions

[rgregoryb]

Google " premierz 300zx hesitation"