I just rebuilt the turbo for my LBZ in my Hummer. During the rebuild I added a KC Turbos 10 blade exhaust wheel and billet compressor wheel. I also replaced the vane position sensor and solenoid with authentic Garret parts. The truck seems to run, drive and build boost fine. However at idle the turbo seems to be cycling. When this happens the RPMs go up and down by about 60-80, not much. I do have a P003A code. All the threads I've read about that code don't seem to mention this particular problem though. Here is a link to a video:
Turbo cycling at idle
- Thread starter NickInMN
- Start date
The truck was up to temp in that video. I am going to try putting the old vane position sensor back in and see if that helps. If that doesn't change anything I'll have to find someone locally that has a Tech2. I'd rather not bring it to a dealer, but I suppose that is a last resort.
I had this happen. That stupid p003a ended up being my FPR. The FPR was causing the idle to to go up and back down a bit like you are describing. In doing so often enough it won't allow the vanes to sweep thus setting a P003A. I changed out the FPR and It was fixed. These trucks relearn the vane sol/sensor on their own, atleast lmms do.
Interesting. I did replace the fuel filter and the feed line. I noticed the truck has a hard start and the truck seemed to be losing prime. I rebuilt the filter head today and now the prime seems to hold (after a few hours the primer is still stiff). I guess I may as well give it a shot before I screw around with the sensor.
I finally got this resolved. It wasn't an issue with fueling. I think when I reassembled the turbo I didn't quite have the hot side aligned correctly. After taking the turbo out and pulling it apart again I re-indexed the vane plunger and put everything back together. Everything is working as it should now. A little frustrating because I can't pinpoint exactly what was wrong, but I'm just happy it is fixed.