MrBoost
20+ Year Contributor
- 31
- 0
- Jan 3, 2003
-
Colorado Springs,
Colorado
Ok guys, need some major help here.....some of you might remember my problems, but I still have not found the cause. I have been having issues with my car and have not been able to drive it now for almost 2 years!!! I have not been able to consistently work on it, but I really would like to get this problem solved! I recently got so fed up I took it to a local DSM shop nearby. They are stumped. The only thing they could recommend is to replace the engine wiring harness.
Background: I did a 1g head / intake manifold / TB swap into my 2g, along with a pair of HKS cams (264/272 combo). I put everything together, and had a small fire that fried the front o2 sensor wire, along with some of the alternator wiring. (The fire never touched the main engine harness, just the o2 sensor wire leading to the harness plug. Aside from that, the other affected wires were on the front chassis harness, which the alternator wiring is part of). Well, I replaced the affected wiring (which was not much, and I am decent with a soldering iron), but ever since then I have been having the following issues:
Symptoms: Get in the car and start her up (which usually takes a couple times before she stays started) but then the car revs to 3k RPM on its own, then slowly drops down and just idles erratically between 800 - 1800 rpm. Once the water temp is up, she can stay idling there on her own (as long as I dont pull fuel with the AFC or DSMLink). Between 0 - 3k RPM it smells and sounds (some backfiring.....probably unburnt fuel in the exhaust) like the car is running super rich, but when you get above 3k RPM, it smooths out and seems (sounds) fine. Plugs get extremely fuel fouled after a short time. The only problem I have after 3kRPM is that she WILL NOT hold a particular rpm. Even when I just slightly depress the accelerator and hold it perfectly still, the motor just keeps slowly building RPM's! Then when I let off, it doesnt just drop RPM's back down like normal, it drops them S-L-O-W-L-Y.....
car is running super rich, but the o2 voltage is dead between 0-3k RPM.....voltage starts at 0.04V, then slowly drops to 0.00V at idle. (YES, those are correct numbers!!). Above 3k RPM o2 voltage starts to cycle normally!
o2 sensor is brand new (oem sensor)
I have replaced the ECU 4 times now, just to make sure thats not the issue.
ECU is throwing no codes, once in awhile it will throw the REAR o2 sensor code (this strikes me as odd though, because my MAP sensor is not hooked up because of a 1g head swap).
Fuel pressure is rock solid at 43 PSI at the rail.
Spark is fine to all cylinders
Compression is 150-145-145-150 (dry test)
Timing marks are PERFECT
All fuses are fine
No matter the injector size (Ive tried 660s, 550s, stock), symptoms are the same.
TPS is new/tested and is fine
So what do you guys think?? Any other ideas before I pull this stupid harness out and replace it? I really dont think thats the problem, because the fire never touched the main harness. Could a short in the o2 wiring fry something downstream of the sensor? What about some sort of vacuum issue?? Someone mentioned this once, but if it were vacuum, why would the car act normal above 3k RPM?? I also know the resistor on the firewall is directly before the injectors in the wiring path to the injectors.....anyone ever hear of one going bad?? I am totally perplexed ..SOMEBODY PLEASE HELP ME!! Thanks in advance!
Background: I did a 1g head / intake manifold / TB swap into my 2g, along with a pair of HKS cams (264/272 combo). I put everything together, and had a small fire that fried the front o2 sensor wire, along with some of the alternator wiring. (The fire never touched the main engine harness, just the o2 sensor wire leading to the harness plug. Aside from that, the other affected wires were on the front chassis harness, which the alternator wiring is part of). Well, I replaced the affected wiring (which was not much, and I am decent with a soldering iron), but ever since then I have been having the following issues:
Symptoms: Get in the car and start her up (which usually takes a couple times before she stays started) but then the car revs to 3k RPM on its own, then slowly drops down and just idles erratically between 800 - 1800 rpm. Once the water temp is up, she can stay idling there on her own (as long as I dont pull fuel with the AFC or DSMLink). Between 0 - 3k RPM it smells and sounds (some backfiring.....probably unburnt fuel in the exhaust) like the car is running super rich, but when you get above 3k RPM, it smooths out and seems (sounds) fine. Plugs get extremely fuel fouled after a short time. The only problem I have after 3kRPM is that she WILL NOT hold a particular rpm. Even when I just slightly depress the accelerator and hold it perfectly still, the motor just keeps slowly building RPM's! Then when I let off, it doesnt just drop RPM's back down like normal, it drops them S-L-O-W-L-Y.....
car is running super rich, but the o2 voltage is dead between 0-3k RPM.....voltage starts at 0.04V, then slowly drops to 0.00V at idle. (YES, those are correct numbers!!). Above 3k RPM o2 voltage starts to cycle normally!
o2 sensor is brand new (oem sensor)
I have replaced the ECU 4 times now, just to make sure thats not the issue.
ECU is throwing no codes, once in awhile it will throw the REAR o2 sensor code (this strikes me as odd though, because my MAP sensor is not hooked up because of a 1g head swap).
Fuel pressure is rock solid at 43 PSI at the rail.
Spark is fine to all cylinders
Compression is 150-145-145-150 (dry test)
Timing marks are PERFECT
All fuses are fine
No matter the injector size (Ive tried 660s, 550s, stock), symptoms are the same.
TPS is new/tested and is fine
So what do you guys think?? Any other ideas before I pull this stupid harness out and replace it? I really dont think thats the problem, because the fire never touched the main harness. Could a short in the o2 wiring fry something downstream of the sensor? What about some sort of vacuum issue?? Someone mentioned this once, but if it were vacuum, why would the car act normal above 3k RPM?? I also know the resistor on the firewall is directly before the injectors in the wiring path to the injectors.....anyone ever hear of one going bad?? I am totally perplexed ..SOMEBODY PLEASE HELP ME!! Thanks in advance!
