I ran my gas down to 1/8 tank and went to refill the tank, the car started idiling funny and shutting off at red lights. The low fuel may have nothing to do with the issue, as the tank had been restored before purchase of car. But i changed my fuel filter in case it did happen to pick up some trash in the tank. Fuel filter was not dirty or clogged. Replaced Mass Air Flow but it made no difference. Before i start swapping out everything from my parts car, i thought someone may have had this before. I didnt see anything on search. Here are the symptoms:
1. idles fine one minute, next time you stop, it may drop idle down to 500 or
even shut off the car, but will start right back up.
2. Can feel hesitation or like it is holding back when running down the road,
but not all the time, just random.
3. Blows out haze of gassy smelling smoke when it idles low and starts cutting out, like
it is getting too much gas and gas is not being burned, backfires out of
tailpipe area.
4. DOES NOT DO IT ALL THE TIME, JUST ERRATIC! Will always start back up.
5. Initial startup does not happen on first try like in the past, but WILL start.

It may do all this and then run down the road for 20 minutes like it just left the showroom and nearly make you forget the problem was there.
Does ECU need resetting and how to do that? Any suggestions on what to replace or adjust?
Was planning on taking it on a 4 hour trip next weekend, but not with this problem.

 

This has been discussed before, but... If it comes and goes, it is most likely electrcial VS. mechanical. Most likely a bad connection somwhere. I would start with the usual suspects like the connection to the AFM. Take off all the connectors and clean the contacts really good with some electrical cleaner and check for damage. I would bet that your problem is a bad connection.

Rod.

 

I feel hesitation going down the road too - but not if the tank is within five gallons of being full! I've tried all the usual fixes except pulling the fuel sending unit or tank. In the meantime, I keep the tank totally full and in runs perfectly (1981 280zx NA). Any ideas??

Thanks, Jeff

 

Then you most likely have an issue with the return line or purge line/charcoal cannister...

Rod.

 

I have checked every ground and cleaned every connector that i know exists. I also replaced the fuel filter, spark plugs, plug wires, distributor cap, rotor button. I have swapped out MAF and ignition coil and same result. (MAF and coil I swapped in, could be bad,as they are old parts). Someone locally suggested that since it is random, that it could be the fuel pressure regulator, idle control valve, MAF, coil or the pump going out. This started happening when i let my gas get down low. Once I replaced all plugs etc. it ran like a charm for a few minutes and then went right back to it's old ways. I drove it to work this morning, a 12+- minute ride. It drove like a new one. I have a friend who has a ZX, I'm going to pull off my AFM and see if it will run on his car. That way I can eliminate the AFM if it runs on his car. (of course mine is running fine this AM, so can the AFM come and go before it goes out or is it poof and it is gone? This is getting frustrating, my wife gave me the cup holder and shift **** from MSA for my car for our anniversary today and i want to put it in, but the car is running crappy.

 

got a spare Fuel Regulator you can trow on quick from your part's car? if so try it out real quick.

 

have you checked the operation of the cylinder head temperature sensor while the car is having it's issues?

 

OK, I'm back from my anniversary weekend out of town and I checked the cylinder head temperature sensor, like jfairladyz suggested. The plastic connector will spin around inside the threaded sensor shaft. The one in my parts car is stationary, so I am swapping them out to see what difference that makes. Shouldn't the sensor connector be stationary or does it matter? The tip on the other end spins too, so it wouldn't seem like the connector inside connections are not broken? Will let you know if it makes any difference, hopefully today!

 

had that same problem with my 50AE when i bought it--the ecu needed to be changed out--after all hoses were changed out, all leaks braised or otherwise sealed--properly, to be all stock, still--now works sorta ok--had clutch slave cyl rebuilt--now does it because the clutch master cyl needs addressed. good luck.

 

The temperature sensor did not make any difference. But my son drove the car yesterday and the car acted up on him. He said he jiggled the ignition switch and it cleared it up and it hasn't happened again. So if it happens again and jiggling the switch clears it up, I am going to change out the ignition switch from my parts car. Will let you know how it goes.

 

I think I found the problem. THE BLASTED ECU!!! I have reworked the carbon track on my afm and replaced a lot of crap- plugs, plug wires, dizzy cap, rotor button, fuel filter, cylinder head temp sensor and swapped out a used fuel pressure regulator and ignition coil. But it still ran like crap one minute and great the next. I was ready to give up, tired of the backfiring and shutting off and fouling plugs from running too rich. My cousin from Latham NY was in Georgia this weekend. We started talking about his car business and our love for Z's. He wanted to know why I didnt drive it to the family reunion and I told him what it was doing and what all I had replaced. He told me to pull the ECU from my parts car and just plug it in. I thought it was a major undertaking, but the 35-pin plug just pops out and in to the new ECU. It fired right up and ran pretty good, so i shut her off and pulled all my plugs and cleaned them up from where the car ran rich, and put them back in. It ran fine for about an hour last night, running trips around town. It drove perfect to work this AM and perfect down to the post office and back. So I think (knock on wood) my problem is solved. He also has access to many parts in NY, so I have found me a source other than my parts car. I am excited again, now that my money won't go to paying for a repair, but i can get back to the painting project.l