High idle, Fouled plugs..what could it be

[jonzzer]

Okay so my problem is most likely a few things that are all having an effect. I swapped a 82zxt into my 77 280z. It has an idle of 1300-1500 cold and warmed up. It also is fouling plugs after only 10 miles, they're all black not wet with gas. tested the primary resistance in the coil and got 1.1ohms which is out of FSM specs, secondary was fine. Ive pinched the AAR and it didn't effect the idle any(quick blue tech tip). i applied vacuum to the AAC and i can see the flap moving so its good. I did remove the EGR since the msa downpipe doesn't have a hole, i made a block off plate. I want to remove the VCM since I've unplugged both plugs to it and no change. I thought a vacuum leak but i don't hear any hissing. Im at my wits end on this thing. i haven't tested the FPR yet but plan on it.did screwdriver test on injectors and heard them all clicking, also thought it was the 02 but no way to test it, the green led comes on in the "on" position when cranking then no light when running.?? heard it means bad 02? Ive looked all over the FSM but most of the test you need a special Analyzer to perform the tests. Sorry for the length, just really need some input

Thanks Jon

[DuoWing]

If the car is warmed up and running the ECU light should be blinking. If it's not or the light is staying solid on while running than the O2 is bad. When I was running the 280ZXT electronics I remember a bad O2 would make at least to me really sluggish low end. You can remove the VCM with no problem, also try pinching off the hose to the AAC and see if that makes any difference. I remember I got rid of that as well. Before I finally converted to the Z31 ECU/MAF I had gotten rid of everything but the air regulator. There's also another valve that could have potentially gone bad. It's the VCV that branches off of that little 4-way split coming off the J-pipe and goes into the manifold. This can be removed and plugged, I believe for that I used a drain plug that was the same size as the L28 oil drain plug. Also try spraying starting fluid all around the manifold to see if there are vacuum leaks, or even remove the oil cap from the valve cover and see if it makes much difference. If there's little to no change it would indicate a vacuum leak, if there's a big change or almost dies then you're good. Or relatively good, try hooking up a vacuum gauge to the manifold and see what's going on.

[jonzzer]

guess ill be buying an O2 sensor. know of any drawbacks to taking off the vcm, things like rough idle, hard cold starting? ill keep the VCV for now, i dont have a blow off yet and im still trying to dial in the boost settings( just swapped stock controller for nxs one). when i take off the oil cap the engine revs maybe 100rpms down for a second then jumps back up so i must have a a good sized vacuum leak. but would that account for the fouled plugs? Wouldn't that extra air lean out the mixture?? The boost gauge is showing 19-20 mmHg at idle...no idea what that means,but i know it should be around 15-17. oh and pinching the AAC dint effect it to greatly maybe a 100 rpm drop, but pinching the line to the from the intake to the vcm dropped it significantly.probably the computer readjusting the idle...

Thank you Duowing for the insight, Did you see a big difference in running the Z31 with Nistune? im temped to try megasquirt but the Z31 is a lot cheaper.

[DuoWing]

Personally I never saw the big difference in running the Z31 ECU that everyone claimed, but I'm actually not convinced my car was ever running as good as it could have been. I really liked the Z31 swap mainly because the MAF was alot smaller, when you run Nistune or a later turbo ECU you can get better fuel maps that helps fuel economy a bit, plus you have the added bonus of the ECU at least able to give you some codes on when some of the sensors go bad. I don't remember exactly, but I think you can run the car with having the VCM all unplugged anyway. I remember though when I did end up removing everything from the car, the VCV, AAC, and VCM I had issues with getting the car to idle as my idle would sit way too low about 500rpm. At least this is what mine sat at on an auto. I had to actually adjust the throttle stop plate on the side of the throttle body to raise the idle. After that it seemed to be smooth. With running just the air regulator I never had a problem with cold/warm starts. I had also just unhooked the A/C and never used it. I'm not sure how the 280ZXT electronics would treat it, but my car was at least running to the point where it would fire right up even on nearly 0 degree days.