03-14-2014, 05:52 PM
Join Date: May 2007
Location: Tulsa, OK
Total Cats: 4
Troublingshoot ECU/Car after VVT swap
The MSM engine ate it's bearings, so I grabbed a junkyard VVT engine and dropped it in it's place. The car won't rev past 2.5-3K due to a horrible mis-fire.
2004 MSM chassis/wiring harness
VVT is not currently hooked up.
Plugs are gapped at 25 I think. NGK 6's.
The car fires and idles like a champ. I found a base 2001 timing map that someone from FM uploaded to m.net and loaded it into the car. Also pulled fuel (~20%) from the previous turbo map. I am getting reasonable AFRs during the increasing revs and including the mis-fire event (11-13). The plugs look fine. The interesting deal is during the mis-fire the RPM reading gets kicked around (typically down). During the increase of revs, the RPM is correct, but during the mis-fire event, it will briefly show 900 or 1500 or similar . This does not obviously match the tach or the actual engine. I also tried various timing values (11-25) and this did not seem to affect the problem.
I suspect it might be a ground issue. The IAT (DIY gm element) seems to be pretty far off all of a sudden. I checked the ground by the exhaust, and looked at the grounds on the Adaptronic adapter board. Both of those seem to be in order.
Did I forgot to hook up one of the grounds?
Are the trigger settings the same for VVT and non-VVT?
Could this be a base timing problem where the Engine and the ECU are not in sync?
If the timing belt is off a tooth (or 2) would these symptoms match?
EDIT: Log uploaded. The VVT columns are default and I never used them with the BP4W. I honestly have no idea what value they are reported.
Thanks for your help!
Last edited by ILoveOffRamps; 03-14-2014 at 06:50 PM.