Erratic idle & rough start
 

First off, I'd like to say that I know almost nothing about the 6.5's.

A guy I know is looking to sell his truck and I'm thinking about getting it. Truck is a 96 Tahoe with the 6.5. I went to take a look at it today knowing it had some engine issues. The truck is very hard to start and when it's running, the idle speed jumps between 500 and 1000 rpm. It also took off on me once, shutting it down right before redline. Also the speedometer seems to move with the tach, not sure if that's related.

He told me it has a new turbo. I spoke to the owner of the shop it's at and he said they tried a new injection pump, it made no difference. He put a new PMD on and it helped clear up some other problems he was having but this problem still exists. While I was there, I checked out the lift pump by opening the t-handle valve and fuel came out. After doing some reading on here and some other sites, I think it might be injector related? How big of a job is replacing the injectors? What else should I look at?

He is asking $2500 for the truck, which is in rough shape. I'm thinking of offering him $1500. Thoughts on that?

Thanks.

Injectors would'nt make the idle jump like that so I would'nt replace them just yet could be a bad new PMD where is the new PMD mounted at anywhere in the engine compartment will lead to premature PMD failure and even with the issues the truck is having $2500 is not a bad price

Thanks for the reply. The PMD is back in the stock location. If I do get the truck, one of the first things will be the remote mount. Thanks for the tip on the injectors too, I'll see if someone nearby has a known good PMD I could borrow for a little bit.

Be sure to get a heatsync for the PMD in my opinion the bigger the better

maybe the ecu needs a relearn? if the shop changed the IP, did they perform a relearn? is the timing set correctly?

All good questions.

I also forgot to mention the shop said they noticed a bolt holding the IP gear on was loose and they tightened it up. So this all very well could be timing related?

very well timing related. the IP gear is held on with three bolts. so if only one was loose, it shouldnt have caused it to skip teeth, jumping time.

Ok, that's good to know. I'll look into the timing thing. Thanks again. :c:

So I ended up getting the truck for $1k. Took a look at it at work today with our Snap-On Verus. It had no active or pending DTCs, but did have several in history:

P0263 - Cylinder 1 Balance Fault
P0266 - Cylinder 2 Balance Fault
P0269 - Cylinder 3 Balance Fault
etc....for all Cylinders except #7
Also a P0406 - EGR Sensor A Circuit High

Also, got a chance to look at some timing numbers:
TDCO: -0.25
ACT Timing: 6.4
TDCO(2): 8159 (not sure if this is an actual value or what)
DES Timing: 14

Also I noticed the IAT sensor was reading high (about 150*F), not sure if that's normal or not.

Thoughts?

Anyone? I know we have to have some 6.5 experts on here.