brendanj85

Changed my oil and plugs yesterday on my newly rebuilt f20c with 500 miles. Ran great up to this point, changed plugs to Bosch platinum +4s, went to give quick test drive to ensure all is good, and the car after about 5 miles or so just falls on it's face pulling onto the highway. Now I have a flashing CEL and my number 2 cylinders not firing at all. It's clearly getting fuel onto the plug, just no ignition. I switched coil packs around and came to the conclusion all coil packs are good, just for some odd reason the #2 won't work period. I guess the next move would be to trace wires all around, just wondering if anyone has had a similar problem. Thanks in advance

Brendan

brendanj85

Mods are comp clutch stg 5, AEM intake. Ran fine for the first 5 minutes like everthing was good then wack. I put the old plugs (acdelco, but they were working fine) back in, and same problem from the get go. Took out the 7.5 back up and started again still no fire to plug and CEL comes back on.

I was thinking personally that it could be a computer problem but am not sure of a way to solely check the computer. I am also going to be going turbo and am almost ready to go for my ems and am wondering if this would be a smart time to go ahead and do that which obviously if it is the computer, it would be. Thanks.

Billman250

If the coil is not firing, and you know its not the coil, you may have a bad ecu.

look over the wiring very carefully. since the engine was out, the harness may have been damaged.

I would do a continuity test for the wires for that coil going back to the ECU. You will likely find an open.

brendanj85

Okay I checked the cop's. Continuity read 12v dc hot wires across all 4 connectors, the middle (neutral?) reads .02 on all 4 connectors, and the grounds are all good EXCEPT the number 2 connector that is reading +5(+/-.5) volts. Not good. Guess my next course of action is to tear apart this pita harness and back track? Or is their a middle point that anyone knows I can check the ground again? Thanks.

Billman250

That wire you found bad, hook up the voltmeter with a clip. Have the meter clipped to it so your hands are free, and watch it...

Now go around and lightly wiggle parts of the harness, you will pinpoint your break You'll see the volt fluctuate as you make-and-break the connection. Known as a "wiggle test" by old school techs.

brendanj85

I'm doing a little ghetto fob on the ground to over ride the factory one for now.. See if it fixes it then I'll go through the harness another time. I'll keep up to date, thanks a lot billman.

Billman250

Be sure thats a solid ground and not a controlled ground, or you'll fry something.

Billman250

From what I can see there is a common coil grounding at G101 so you should be good with your fix. Wire color is black.

brendanj85

My grounding wire color is white? Or what is the white wire?

brendanj85

I don't know where any wiring diagrams or schematics or anything or even a manual lol so I am unsure of what all these wires purposes are, I'm guessing the white wire is a wire that becomes activated when the ground is disconnected and tells the computer to throw the codes?