- Joined
- Jun 18, 2001
- Messages
- 2,214
Posting for posterity. I hope this helps somebody in the future. I just got done troubleshooting and fixing a really frustrating electrical issue.
The car has an ECUGN and I'm using the coil near plug option.
The car has been running great this year until July 13, 2025, at an Indianapolis Region SCCA event. It failed to complete a single autocross run, with the engine sputtering and backfiring and stalling. We limped it onto the trailer and headed home.
Once we got it back home, it started and ran just fine backing it off the trailer. I parked it and came back a few days later to dig in.
Symptoms:
First start when cold, runs good.
After it warms up, it dies. Restarting at that point results in a car that runs like crap. Misfires everywhere.
Diagnosis steps:
Datalogged it in Tunerstudio with the tooth logger and seeing sync loss. Assumed (incorrectly, keep reading) that the crank sensor was failing.
Repair:
Replaced crank sensor. No change. Suspecting crank sensors from parts stores were not reliable anymore, acquired a hall effect sensor that's used in motorsports and installed that with a custom bracket.
Changes to the tune? this sensor is inverted from the stock one, so It required some tweaks to the wheel config in Tunerstudio, but now I have a modern high quality hall effect sensor instead of having to gamble on Chinese repop OE style sensors.
Result: No change in engine behavior, but the tooth logger looked weird:
The blue is the crank trigger, and it's just blips. We should be seeing a square wave like the cam trigger showing the tooth duration.
Now we're getting confused. More digging. And I found it. the grounds on the back of the intake manifold had come loose. This has happened to me before and it fried my stock ECM and sent me in the ECUGN direction. Loctite applied to the nut. I'll start checking it as part of my pre-event inspections.
The ECUGN has a test mode, so we used that to individually fire each injector and each coil. #6 (SparkA) didn't work at all once it was warmed up.
I shipped the unit back to Turbotweak fearing damage. They found some. The spark drivers and the IAC circuits had taken a hit. They repaired it and had it back to me in less than a week. Because Turbotweak is awesome.
But no change.
Same issue. Same weird tooth traces. Bob Baily suggested the adapter board that replaces the CCCI may have taken damage. There's a tach filter on the board that works on the crank sensor signal. Eric at TurboTweak shipped me another adapter board, and...
.....
Drum rollll.....
Boom! We have it! We see teeth!
The car idled for over 30 minutes with the A/C on in 96 degree heat and didn't even stumble.
So, the root cause was loose grounds. The damage was ignition drivers in the ECU and the crank sensor filter on the CCCI adapter board. If you see blips instead of a nice square wave in your tooth logger, check that adapter board. The crank buffer might have taken a hit.
The fancy hall effect sensor? Completely unnecessary, but I'm keeping it.
Big props to Eric Marshall and Bob Bailey for all the support. This was a tough one. But we got it.
The car has an ECUGN and I'm using the coil near plug option.
The car has been running great this year until July 13, 2025, at an Indianapolis Region SCCA event. It failed to complete a single autocross run, with the engine sputtering and backfiring and stalling. We limped it onto the trailer and headed home.
Once we got it back home, it started and ran just fine backing it off the trailer. I parked it and came back a few days later to dig in.
Symptoms:
First start when cold, runs good.
After it warms up, it dies. Restarting at that point results in a car that runs like crap. Misfires everywhere.
Diagnosis steps:
Datalogged it in Tunerstudio with the tooth logger and seeing sync loss. Assumed (incorrectly, keep reading) that the crank sensor was failing.
Repair:
Replaced crank sensor. No change. Suspecting crank sensors from parts stores were not reliable anymore, acquired a hall effect sensor that's used in motorsports and installed that with a custom bracket.
Changes to the tune? this sensor is inverted from the stock one, so It required some tweaks to the wheel config in Tunerstudio, but now I have a modern high quality hall effect sensor instead of having to gamble on Chinese repop OE style sensors.
Result: No change in engine behavior, but the tooth logger looked weird:
The blue is the crank trigger, and it's just blips. We should be seeing a square wave like the cam trigger showing the tooth duration.
Now we're getting confused. More digging. And I found it. the grounds on the back of the intake manifold had come loose. This has happened to me before and it fried my stock ECM and sent me in the ECUGN direction. Loctite applied to the nut. I'll start checking it as part of my pre-event inspections.
The ECUGN has a test mode, so we used that to individually fire each injector and each coil. #6 (SparkA) didn't work at all once it was warmed up.
I shipped the unit back to Turbotweak fearing damage. They found some. The spark drivers and the IAC circuits had taken a hit. They repaired it and had it back to me in less than a week. Because Turbotweak is awesome.
But no change.
Same issue. Same weird tooth traces. Bob Baily suggested the adapter board that replaces the CCCI may have taken damage. There's a tach filter on the board that works on the crank sensor signal. Eric at TurboTweak shipped me another adapter board, and...
.....
Drum rollll.....
Boom! We have it! We see teeth!
The car idled for over 30 minutes with the A/C on in 96 degree heat and didn't even stumble.
So, the root cause was loose grounds. The damage was ignition drivers in the ECU and the crank sensor filter on the CCCI adapter board. If you see blips instead of a nice square wave in your tooth logger, check that adapter board. The crank buffer might have taken a hit.
The fancy hall effect sensor? Completely unnecessary, but I'm keeping it.
Big props to Eric Marshall and Bob Bailey for all the support. This was a tough one. But we got it.
