I think this forum is better for technical advice, instead of posting in my performance thread.

I'm having an injector issue on cylinder #3. Sometimes the car misfires, and sometimes it runs smooth as glass. There seems to be no pattern behind the symptoms.

Bill Buttermore helped me diagnose it today. Using a rubber hose as a stethoscope, we determined that when it misfires there is no pulse in the #3 injector. We swapped in a used injector from the junkyard, but there was still no pulse. Resistance was the same on all injectors, including the junkyard piece. We did not have a test light to check power to the injector, but Bill put a voltmeter on a few sets of the injector wires and got a reading of 13 volts :?. Not exactly sure what that meant. So we put the original injector back on, I started to leave with the motor misfiring like crazy, and before I got to the end of the street it was running smooth again.

I don't think it'* fixed, because it has been running so erratically all week. I'm going to get a test light to check for power to the injector the next time it misfires. What could be causing this? The injector has to be decent if it runs smooth from time to time..... so what could be the cause of an intermittent injector failure? Bad wiring? Bad injector driver in the PCM? Whatever it is, when it'* good it stays good for a while, and when it'* bad it stays bad for a while. Very mysterious.

Ideas?

The fuel injectors are supplied by battery voltage as soon as car is turned on, you can measure it at the pink wire on the injector plug. The other wire on the injector goes to the computer. The computer electrically grounds that wire for the duration of the injector pulse required to complete the circuit and energize the injector. Therefore if you have the 12 volts to the injector I would be looking at the wire from the injector to the computer for an intermittent connection or it could be a problem in the computer quad driver module and you would need to replace the computer.

Flatlander

Have you checked the wires going to the injector? My '99 GP GT had a the same problem as yours accept it was on the back 3 cylinders. All three injector wires were stripped of their insulation from rubbing against the engine cover. I taped them up with some high temp elec.tape and I haven't had a problem since.

Check for continuity while having another person wiggle the wires. Sounds like you have a wiring issue.

After doing some testing of the injector wires, I'm pretty sure the problem is with the injector itself. Tomorrow I'm going to swap it over to a different cylinder and see if the misfire follows the injector. Results will be posted. Any other advice while I'm working on it?

I swapped the #3 and #1 injectors today, and the misfire followed the injector over to #1. Guess I just need a new injector. I also got a "P1200 Fuel Injector Circuit Fault" code. Does this indicate a different problem, or just reiterate the fact that the injector is faulty?

Depending on your needed turn around I might be able to find you one on Friday..but no sooner.

Thanks Boosty, but I can find one here if I need it. I posted a request for an injector on the off chance that somebody could send me a cheap one by Wednesday. I have a wrecker here that can get me an injector, I just thought I could find a better price than $20. Thanks anyway!

I don't wanna tell you what the "good:" junkyard charges.. you'd cry. I thought I saw that one..thought it was by this Friday..