Having an issue I just can not figure out. Have posted on another group and I got some great answers from some people, while I thought this was fixed I guess I am wrong lol. Build is a built ly6 with a 230/235 cam and twin turbos in a 15' Camaro E38. While cruising and "sometimes" WOT I will have this very quick abrupt "shake" which feels like a severe misfire/ car turning off for a 10th of a second. Hptuners shows the rpm dropping to almost 0 when this happens but the tach does not move (assuming delayed and too quick for it to show). No timing drops, fuel pressure, air-fuel, nothing lol. Really stumped if this is some mechanical issue or tune related. brand new crank sensor with the new motor and I did do a crank relearn, not getting a single code. Car drives great when it does not happen, you wouldn't know any different. This seems to happen after a new flash but I don't have enough evidence to confirm that yet. Wot is generally smooth but sometimes this issue will carry into it every blue moon. At this point I will pay someone if they can figure this out or point me into the problem, Feel like I've tried everything and winter is approaching lol. I have attached a tune and log, issue generally does not happen this close together but did today. I should also mention this happens on full speed density and maf only, I am on the 2 bar enhanced OS as-well.
Hmm, I cant remember if E38 uses crank or cam sensor for RPM calculation, but maybe try logging cam sensor counts and medium res counts to see if you can pick up a skip in the signal?
A while back I diagnosed an issue for a customer with a whipple lsx376 that for some unknown reason had a camshaft start walking backwards out of the block! As the cam gear got further away from the sensor it started off doing odd things like very minor mystery shakes and misses and gradually got worse. Not saying yours is internal mechanical like that, but maybe still an intermittent cam or crank signal quality issue.
Check for a loose ground wire somewhere. The GM harness has grounds to both cylinder heads as well as chassis, a loose ground wire can play havoc with the ECU.
Figured I would update everyone as I hate when people don't. I put it back on speed density and it drives a-lot smoother, moved around my power wires (maybe something was loose) logged the PID's Caudle stated, could not find any abnormalities. Been giving it some good driving time. Cleaned and sanded every ground wire (again). Issue has not presented itself at all since making this post and putting it back on SD. Crossing my fingers it will stay this way but it's running really good. Personally I feel like it was something electrical, possibly the maf being bad or a combination idk (rather run SD on 20lbs anyways). Really appreciate everyone throwing out ideas and helping as there isn't much of that anymore, I will update this thread if anything presents itself but I hope this update can help someone in the future.
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Originally Posted by nty1234
