broxma
Well-known member
It's technical in nature so I am putting it here. First off, I wanted to say there should be more problem resolution posts around here considering the age of these vehicles and the issues we run into. That being said, here is what happened. Hope it helps someone later on.
The setup is somewhat unimportant but my car is running an Evo VIII ECU so OBDII protocol. The first time this happened, I presented with 3 CEL codes, P0340, P0335 and P0122. The car sounded like it was running on two cylinders. The solution the first time was a pinched wire on the COP plate on the head.
Few days ago, I'm strapped to the dyno and I present with the exact same codes, but now, the car is running fine. It does however have full blown knock above 3000 RPM. The only recent change to the car has been the DNP manifold, the new wastegate and a new exhaust. I log knock and see at 3000 RPM is shoots to 9 counts of knock and stays there. All other functions of the car are totally normal. AF ratio's are kind of odd, bouncing a lot more than normal. So what is causing this?
Same thing as before but different. Essentially, either the starter wires or the alternator wires are arcing to the block or a frayed wire at a connector or thin shielding is allowing positive juice to get to the block. What this does is it throws any sensor with a 5 volt reference signal (Cam, Crank, TPS) into a fault. it also sets the O2 sensor into havoc mode. Since the car was still running on all 4 cylinders I could be fairly sure it wasn't part of the ignition causing this. Since I had pulled the same codes this time as before, I worked under the premise that the problem was going to be another positive wire arcing on the engine itself. In fact upon inspection, there were several places it could have come from. The starter solenoid trigger wire was exposed at the connector. The alternator wires had rubbed thin against the alternator due to my wiring route. The secondary igniter, which I subsequently removed, had several wires with cracks in the shielding.
Essentially, at one of those points, I was shorting onto the motor. In addition to throwing the three codes I mentioned, after I fixed it, the idle totally smoothed out, even without any idle control. So, if you are doing a restoration or hunting down electrical gremlins, remember to double check the little things. All the things I moved or repaired today were things I had gone over previously and assumed I had done right the first time. Anyone who knows me or has looked at the work I put into my VR4 knows I'm not one to cut corners, so even the best of us sometimes screw up. Hopefully, if anyone has similar problems in the future they will find this post, using search hopefully, and get in touch with me. That being said, tonight was a win for deductive reasoning and electrical troubleshooting. Nothing irks me more than trying to find the source of an electrical problem. Hopefully, none of you will have to spend the 5 days it actually took me to figure out what was wrong if this happens to you.
/brox
The setup is somewhat unimportant but my car is running an Evo VIII ECU so OBDII protocol. The first time this happened, I presented with 3 CEL codes, P0340, P0335 and P0122. The car sounded like it was running on two cylinders. The solution the first time was a pinched wire on the COP plate on the head.
Few days ago, I'm strapped to the dyno and I present with the exact same codes, but now, the car is running fine. It does however have full blown knock above 3000 RPM. The only recent change to the car has been the DNP manifold, the new wastegate and a new exhaust. I log knock and see at 3000 RPM is shoots to 9 counts of knock and stays there. All other functions of the car are totally normal. AF ratio's are kind of odd, bouncing a lot more than normal. So what is causing this?
Same thing as before but different. Essentially, either the starter wires or the alternator wires are arcing to the block or a frayed wire at a connector or thin shielding is allowing positive juice to get to the block. What this does is it throws any sensor with a 5 volt reference signal (Cam, Crank, TPS) into a fault. it also sets the O2 sensor into havoc mode. Since the car was still running on all 4 cylinders I could be fairly sure it wasn't part of the ignition causing this. Since I had pulled the same codes this time as before, I worked under the premise that the problem was going to be another positive wire arcing on the engine itself. In fact upon inspection, there were several places it could have come from. The starter solenoid trigger wire was exposed at the connector. The alternator wires had rubbed thin against the alternator due to my wiring route. The secondary igniter, which I subsequently removed, had several wires with cracks in the shielding.
Essentially, at one of those points, I was shorting onto the motor. In addition to throwing the three codes I mentioned, after I fixed it, the idle totally smoothed out, even without any idle control. So, if you are doing a restoration or hunting down electrical gremlins, remember to double check the little things. All the things I moved or repaired today were things I had gone over previously and assumed I had done right the first time. Anyone who knows me or has looked at the work I put into my VR4 knows I'm not one to cut corners, so even the best of us sometimes screw up. Hopefully, if anyone has similar problems in the future they will find this post, using search hopefully, and get in touch with me. That being said, tonight was a win for deductive reasoning and electrical troubleshooting. Nothing irks me more than trying to find the source of an electrical problem. Hopefully, none of you will have to spend the 5 days it actually took me to figure out what was wrong if this happens to you.
/brox