I'm running into a issue that has me scratching my head. I'm hoping someone has run into something similar and can lend some insight.

Car is a 2003 3.8l with xona 73mm turbos with green/7PSI springs installed, 1300cc injectors, walbro 450, and a mafless cobb tune.

The issue is that while on track the car will occasionally go into limp mode with code P1508 (bad dme). After a restart the car is back to normal. It seems to happen more often than not at high load/boost (above 6k in 3rd and 5k in 4th). I've attached two logs of it occurring, highlighted in red is when the cut occurs.

The car has been pressure tested multiple times with a couple of small leaks addressed.

I have no reason to think the DME is bad and apart from when this issue occurs the car runs great. There are a million parts I could try swapping but to save my wallet and sanity I'm hoping someone else has run into this issue.

 

Who is your tuner?

 

Been working with Sam who has been more than helpful but we’re running out of ideas.

 

I'm reading that the engine monitors the acceleration of the flywheel after each cylinder performs a power stroke. One cylinder could be lacking. It could be a missfire: check plugs, plug gap, coils. Could be a crank position sensor. You could have a blown head gasket. You could have some knock, check fuel quality. That is what I would test first.

 

I have less than 3k miles on a new engine and plugs. It’s funny you mention crank position sensor, that’s what I was thinking as a possible cause as well since it seems to be an issue more often at higher rpms.

 

What are your plugs gapped at? It is possible that you are blowing out your spark. I'd start with the easy cheap stuff first. I think when a crank sensor fails it is usually a total failure, but maybe not in your case. It is possible too.

 

Have no idea if this relates at all but when my 2008 Cayenne S started intermittently going into limp mode it ended up being the crankshaft position sensor. It threw a code for that as well as air mass ahead of throttle value implausible. When it was happening a restart of the engine would reset it to normal.

 

Interesting, how did you end up determine it was the CPS?

 

Indy shop in OC CA, Cape Auto, diagnosed it then replaced it. Now runs great.