| Ok, so I've been troubleshooting an idling issue with my '91 NA-TT swap for a few months now. The motor works fine cold, and once it warms up it will drop down to 700 RPM like it should.
The problem is that I noticed if I turn on the headlights the idle will modulate between ~550 and ~1000 RPM. It eventually levels off back to 700 but soon after starts modulating again, finds its normal spot and so on and so on. Next is that, while driving, if I shift to neutral (MT) the RPM's should drop back to the 700 RPM idle spot but instead it drops completely and the the motor stalls. Sometimes it will catch itself just before it stalls, meaning the RPM's get so low that the lights come on on the instrument cluster because the ECU thinks the motor is off. When it catches itself, it will modulate just like when I turn on the headlights. When I do drive the Z like this, I will tap the gas when I put it in neutral once it goes under 700 RPM to keep it from stalling. I have been researching for months here and there when I have the time to try and figure out this issue. So far I have:
-checked/cleaned all connections for clean contacts
-cleaned/oiled air filter
-replaced fuel filter
-cleaned throttle bodies
-replaced AAC valve
-adjusted idle screw on AAC valve
-Checked ECU (code 55)
-Battery has 12.45 volts when car is off
-installed grounding net
-checked for vacuum and fuel leaks. With the car on:
all accessories off, idle sits at ~750 RPM= 13.98V
all accessories on, idle sits at ~850 RPM= 12.19V
hold the rev at 2000 RPM= 13.88V If I turn just the headlights on, idle modulates between 550-1000
-lowest reading during this was 13.36V Here is the info on my headlights (HID):
XENTEC
8k
DC 9V~16V
35W +/-3W I have also noticed that I am running fairly rich. The car will backfire here and there and those who have seen the exhaust when it backfires say that it will shoot some flames out. My gas mileage is not that bad but I know it could be better. Usually about 250 miles to a tank. My next thought would be my tune...I got my ECU chipped when I did the swap and it was done by AAA-Hiperformance Auto in Texas. I'm not accusing him or anything bad but I did hear some issues about him and where he got his tunes from. Other thoughts would be TPS, CAS, PTU adjustments, but I'm not real sure where to go from here. Any thoughts or suggestions on what to look into next would really help, Thanks!
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