85 300zx N/A rough idle, running rich

[DarkSect]

So one morning I woke up, and my 1985 300zx N/A 2 Seater automatic started with the following problems : Rough idle, running very rich, and low power (no balls). The car will occasionally die as well if you don't keep the rpm's up. I've already gone through the works with this thing replacing the ecu, maf sensor, fuel filter, o2 sensor, Catalytic converter,fuel injector had the alternator tested and I'm going to replace the spark plugs tonight. Fuel pressure is normal at the gauge. This thing is going to drive me insane if i don't get it fixed. So any help/tips or suggestion will be greatly appreciated...thanks!!

[DarkSect]

Also on a side note, the ecu is giving back a code for the Air conditioning, which doesn't work. And the coolant temp. sensor, which i believe was a code given prior to the recent issues, and am unsure if this could cause a problem that big?

[evildky]

CTS code makes the car run extremely rich all the time, I would start by fixing that known problem. When was the timing belt last changed? ignition timing checked?

[DarkSect]

I replaced the CTS no change, but the car got substantially worse overnight, its no longer driveable and it now takes about a 20 mile runway to get up to speed. there's no way timing could be that far off, and it couldn't be the MAF. I'm running out of options here..

[evildky]

You said fuel pressure is normal at the gauge? This means you T'd into the pressure line and installed a gauge and read 40 ish psi at idle right? Did you check the ignition timing?

[jfleenor]

I have a similar problem with my 84 Z31 Turbo. See below (copied from another forum who doesn't have answers or suggestions.

My 84 50th turbo, 5 spd will not run at idle, and runs rough when I keep the rpms at 2500 or over, at operating temp. runs great when cold. I am not throwing any codes, it has a new cat, o2 sensor, chts/cts, the egr is working and has new tubes, and I have swapped the ecu. Idol/air, tps seem to be ok too. It has 139K on it and has good compression, doesn't use oil, doesn't over heat, and doesn't leak. What am I missing? Could it be the MAF? I'm in CA, so I have to live with the smog Nazis.

This car reminds me of an old Yamaha Virago motorcycle I had. Seemed that people loved them, but at the same time, everyone had major issues with them and had to invest a bunch of time just to keep them running.

[evildky]

These cars aren't so well loved but should be, they tend to be quite reliable.

Your 84, starts and idles fine when cold? Only has idle problems when warm or warmed up? This is the typical CTS issue, you said yours was replaced was the pigtail also replaced? Could be an issue with the pigtail or the contacts at either end. Yes the maf can cause similar issues.

[jfleenor]

Thanks for the suggestions. I appreciate the help. I have not replaced the pigtail yet. I am swapping the MAF today, and I have ordered a new pigtail. Hopefully, it will fix the problem.

[DarkSect]

Yes, the gauge is reading around 40 psi where it is T'd in, I'm thinking there could be fouled plugs...but what are the odds there? I have no idea where to go from here.

[evildky]

I replaced the CTS no change, but the car got substantially worse overnight, its no longer driveable and it now takes about a 20 mile runway to get up to speed. there's no way timing could be that far off, and it couldn't be the MAF. I'm running out of options here..

you said you replaced the cts but did the code go away? cts, O2 and fuel temp all cause the car to run rich, the cts and it's pigtail are common issues that can cause mass overfueling causing the car to flood out.The overfueling problems always present worse when warm as a cold engine require more fuel. The TPS or maf can also cause the car to not want to accelerate or rev.

[Desert Rat]

dredging up an old thread here....

Similar issue with mine, but once warm, the car runs a lot better. I do have a new CHTS and pigtail that I haven't installed yet.

When warm the idle still jumps around a little, but it pulls hard. The rough idle and the rich smelling exhuast are more prevelent when the engine is cold.

Still the CHTS and pigtail?

[evildky]

Bad CHTS generally makes the car hard to start when warm. When cold it will run rich possibly to the point of stalling. If yours runs better warm than cold the CHTS is not likely your issue, I'd have a look at the FICV and IACV.

[Desert Rat]

Acronym hell....IACV is the Idle air control valve...whats the FICV?

For the IACV, I found Standard products IACVs on Amazon....two different models - AC341 and AC342. Both say they're compatible, but there's a $50 price differential betwen the two, and I have my doubts on that. OEM ones are close to $200.

Hate to throw expensive parts at it just hoping they work.

Something else the car does on warm idle...it idles up to 1100 and runs real smooth, then falls off to 800-900 and idles rough, and repeats this about every 5 seconds. I had originally suspected a vacuum leak causing this, but given the miles of vacuum lines on this thing, that's also a lot of trouble shooting to do.

Any thoughts are appreciated.

[evildky]

FICV also known as FICD, fast idle control valve/device. I wouldn't just replace them, I'd take them off and clean them up and adjust them.

[Desert Rat]

is there a tutorial on that someplace? as I look at these parts I'm not sure what 'adjustment' is there.....

Thanks for the replies.

[evildky]

FSM details how to check and adjust, it's just a screw on the end.

[Desert Rat]

cool...thanks.