2G Voltage Dropping to ECU

[ileagleracing]

I’ve got a 95 TSI AWD that is currently in the shop for a head swap (when they swapped in the rebuilt motor from my 98 they didn’t install the 98 head & the head off the original motor must have been machined slightly and I got tired of telling fellow competitors that it wasn’t cammed). The 98 head is in, but they’ve run into an electrical issue.

Apparently the voltage to the ECU will frequently drop down to 8-9 volts and the car will run like crap. It doesn’t seem to be a broken or crossed wire as the car will exhibit this behavior during idle while parked. I had the DSMLink upgraded to V3, but I think this problem existed to some extent before this stint in the shop, as the car would idle very rough after first starting it, but would be fine by the time I’d start to pull up to the start line. Swapping in a stock ECU (or a V2.0 or V2.5 DSMlink ECU) has no affect. The shop the car is at is somewhat well-known for working on DSM/Mitsubishi’s and the mechanic says he hasn’t run into this problem before. Not sure how often they’re actually “looking” at my car at this point but it’s been close to 6 months and I’m hoping someone on ‘tuners might be able to suggest a solution.

Thanks,
Samuel

 

[steve]

Have them check the alternator output and see if the whole system voltage is dropping or just something in the branch to the ECU. If it's everywhere then sounds like time for a new alternator.

 

[ileagleracing]

That's a good idea, I don't think the alternator has been checked yet. I know I haven't touched the alternator since I bought the car, so it could be the original.

 

[jakelandry]

If the shop can't diagnose something as simple as a voltage drop you need a new shop.