I had a few posts last year about my son's '96 na running like crap. Bogging, erratic idle, etc, etc. Changed the pump, got a used pump controller from Z1, chased vacuum leaks, clean IAC valve, ,electrical check on coils, injector connectors, cam sensor, and PTU. All checked out. Eventually changed injectors and fixed the issue. Ran the hell out of the car over several weeks locally with no issue. Car sat this whole semester while son had my truck at school. He took the car back to school after Easter and NOW it acts up. He drove 300 miles back to school with no issues until he got back to his town. Gas was on empty so this morning he filled up. We thought maybe it wasnt picking up gas being on empty. He drove it this morning and it ran fine. Then he shut it off while at the gym. When he came out to drive home it started acting up again.

Anyone have any thoughts on what it could be. Ill be getting the car back this weekend to start diagnosing, AGAIN.

Could the ecu cause erratic running issues?

Reading that I was going to ask if you had tried swapping to a good known ECU. Also maybe try bypassing the FPCU and see if the issue comes back. Throwing parts at it will get very expensive especially if the issue is compounding across components. You've got to isolate the issue which takes a lot of time, so its the choice you have to make. Spend lots of time but less money or vice versa.

I had an issue a long time ago when I first hooked up my SAFC with a bad connection on the MAF wires creating similar condition because the car was going and and out of limp mode. What condition is the EFI harness in? How are the connections at the sensors. Lots of heat and age wreaks havoc on the harnesses in these cars.

I remember making a bypass harness for the pump controller. Thought it was fine. Will have to recheck. All the injector connectors were in good shape as well as all sensor connectors. Car only has 80k on it. It had been driven many times locally and pushed a lil hard trying to get it to act up but all was fine. It didn't start until after a long drive, 5 hrs. Don't have another ecu to try. Will have to look into it. I still have the original pump controller so I'll try the original one and see if it changes

I'd drive it with the FPCU bypass for a bit to see how it reacts so you can start identifying things that arent problems.

What does the control unit actually do? How does it run if bypassed?

It modulates the voltage via switching on the ground circuit between two voltages, I forget what they are. Search for "Z32 fpcu bypass". I think CZP has the wiki hosted. When bypassed it just runs at full voltage basically the higher setting.

Thanks. I knew what it did just didn't understand how it worked if bypassed. Basically 12v is default if bypassed. I remember reading about the bypass and evenade the wires for it
Just gotta find em, or make new ones. I also still have the original module for the car so I'll be trying that too.

On a different note. Met my son half way between home and school to swap cars. He drove 100 miles toeet me and car ran flawlessly. We are breakfast so it sat for about 30 minutes then I drove it 200 miles home and again flawless. Will keep posted.

Car sat a couple weeks til Jake came home for the summer. He drove it around town and acted up again. He said it will run fine the he'll hit the clutch and the revs will stay up. After a couple seconds the revs will drop but then once he re-engages the clutch the car will start bucking and surging like in the past. I'm really stumped on what would cause this. This weekend I'll be reinstalling the factory fuel pump control module. Currently running a known good used one we got from Z1

In a completely isolated environment what you describe there sounds like a failing TPS.

He has driven it a few times since my last post and car ran fine. he is paranoid though.

I will look into the TPS.
I did swap the original fuel pump controller back into the car and seems to run fine so no change, for now.

So Son is back at school. Hasn't had issues since going back, a week now. While he was home during summer he was out with a friend and stopped at the drive through. He shut the car off to place order then fired it right back up. While leaving the lot he said it stumbled a lil bit and of course his reaction was to hammer down on it and run it out to 7000...lol. I told him that was an Italian tune-up...lol. That was the only hick up in the last 2 months or so. We never got a chance to look at the TPS.

Not sure if I've mention it in the past or not but we live in the deep south, half hour from New Orleans. Needless to say hot as hell. When he drives in city traffic during the day in the summer I'm guessing the engine bay gets heat soaked pretty bad.

Last weekend we installed a new TPS and so far so good. Crossing fingers this was the fix.

I don't think there's an issue with heat soak on an N/A. I live in Central Florida and I've had no problems.

It isn't normal heat soak like with turbos. When electronics start to fail they become more sensitive to heat.