Help-GTR Behaving Strangely!

[R33]

I had just read Ismail82's post on his idling problem a day before yesterday. And guess what happen? Last night, on my way out, my car suddenly jerked at about 24OOrpm. Anything below that and the engine was okay. So, I had to drive below 24OOrpm. Otherwise, the engine jerked badly - like there was no fuel supply or the ignition was being retarded - although the engine did not stop entirely. After about 1O mins or so, it was okay again. But while cruising, the car would suddenly lose power with a little bit of jerking and after several seconds it wud go back to normal! After stopping, the idle would go crazy...it wud jump to 12OOrpm and go down to 4OOrpm and threaten to stop altogether and then go up again to normal or 12OOrpm. The engine would sound coarser than normal and is sluggish.
Today is the same. What could it be? The AFM? Oxy sensor? Bad fuel? Anyone could help?

[RazorGTR]

Ok could be an air flow meter or a few other things.

check the vaccume hose that goes to the fuel pressure regulator. It could have come off. Another possibility is you blew an I/C Hose, and I would closely check the one entering the front mount they are noted for blowing there.


It sounds like your car is in limp mode which is a safety built in to protect the motor if something is going on it can detect.

[R33]

Thanks Razor. Checked the vacuum hose and i/c piping...all are in good order.
I suspect it is bad fuel as it started to happen after I filled up my tank on Tuesday. Yesterday the tank was quarter full and I filled it up at my usual kiosk. The car was ok both on the way to and back from the office. It jerked a bit in the afternoon on the way to a meeting. Today, the idling was crazy in the morning but nothing happened on the way to work although I hit dead spot around 4OOOrpm for a second or two on 2 ocassions. I will drive around to finish the current fuel and see what happen after that.

[R33]

Ok...a bit of an update on my car. It was not bad fuel for sure. Diagnosis showed it is one of the AFM...as I suspected all along. Replaced one today and will see how the car is doing tonite and tomorrow.

[RazorGTR]

Ok cool let us know. If it was an AFM then your computer would put the car into limp mode which is a safety built into by Nissan.

[R33]

You were right all along Razor. The car was in limp mode all these while due to the AFM malfunctioning. After I had replaced it yesterday, the car is okay so far. The engine revs smoothly and boost builds up nicely like before. Will monitor it for the next day or two.
Razor, cud you tell me whether replacing the stock AFM with aftermarket or bigger AFM from other cars and retuning the mix after that makes any difference?

[phatdex]

When wanting more airflow ppl tend to replace the stock AFM's with Z32 300ZX TT ones as they flow a lot more air.

[RazorGTR]

phatdex while that is a worth while upgrade for higher volumes of air flow, it will not work properly or at all with the factory ecu left the way it is. The signals are a bit different. With an aftermarket ECU such as a power FC, they have a built in feature that you select the air flow metering device. I would suspect how ever that in someone in my position is it possible with the ECU being chipped that you can lie to the ecu to achieve it.