LMM Vane Position Sensor

Cornell

LBZ for life
Sep 11, 2006
1,601
0
0
Minnesota
Last weekend and this weekend I put 68mm Cheetahs on my LBZ and my buddies LMM. Mine went off without a hitch but my friends truck was another story. He had a tint shop... yes a tint shop put PPE manifolds a PPE intercooler, dual fueler, and uppipes on his truck and had them delete the EGR. They way overtightened everything because I had an easier time removing my stock charger that hasn't had a bolt turned on it since it left the factory 100k miles ago. Then they didn't take the time to align the aluminum intake properly and punched a hole through the one side with the dipstick mount and mounted the other side too far forward so it rubbed on that coolant line where the stock airbox sits. Soooo now it has two holes in it. They must have pulled the turbo to do the work they did because the Vane position sensor was all frayed and taped up. That and they hacked up both sides of the tube that goes from the intercooler to the intake riser.

Anyways.... got my buddies truck all buttoned up about an hour ago and took up out for a shakedown. Instantly blew the boot off by the intake riser without even trying. Got that tightened down even more. Did a 30mph roll to 70 and it pulled great and made 40psi without issue, really smooth. Did it one more time and it wouldn't make over 9psi. I wanted to start this thread to get some feedback but I'm going to go out and do some logging and check to see if desired vs. actual vane position.
 

LBZ

Super Moderator
Staff member
Jul 2, 2007
9,905
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B.C.
I'd check for other possible leaks and log desired vs actual vane position. Could be a pinched wire or something that rubbed through.
 

bluessmax

Tabasco Injected!
Nov 4, 2010
1,153
30
48
Lake Charles, la
The underboost code comes from the ecm noticing that you are not hitting your desired boost level. If commanded is say 30 baro (15lbs boost) and actual is 20baro...you will get an underboost code. More than likely your vane sensor causing this...let us know what you find in the log
 

Cornell

LBZ for life
Sep 11, 2006
1,601
0
0
Minnesota
Well I did some logging with the laptop earlier this week and just never had time to get on here. The desired vs. Actual was fine so I don't think it is the vane position sensor anymore. Truck doesn't defuel at all. Once it throws the underboost code the engine goes into reduced power.

Any chance it could be the MAF sensor on the intake bridge?
 

Cornell

LBZ for life
Sep 11, 2006
1,601
0
0
Minnesota
Just a little update, it had a damaged thrust bearing. Most likely from being overspun because of the boost leak.