Intermitent power loss/turbo fluctuation

[Ray Sharpe]

Hey guys. Just signed up a few days ago. Awsome site, been reading for a couple of days straight.
I've got a '99 k2500 ex.cab sh.box Auto. A couple of weeks ago, I hauled my buddy's 4x4 pull truck down to Utica New York (Approx. 6hrs) for a truck pull. On the way down, we encountered some decent hills. About 10 mins. driv :mad: ing in the hills my truck lost power large.
I noticed my turbo was not putting out any boost hardly at all, and there was excesive smoke. I wired the wastegate shut, and just fiddled around with things and eventually I was able to regain some of the boost pressure, although not all of it. Now that I am not towing anything, the truck seems to have most of its power back, but the turbo seems to spool up rather slowly when you tromp on it. One time you go and the boost goes up to 10-12 psi and stays until you let off, the next time you step on it, you have a hard time getting 6psi out of it. I have replaced the MAP sensor, and it has a new air filter. I have owned the truck since 43000mi and it now has 117000mi on it. The IP hasn't been changed since I've had it.

Also, the boost pressure fluctuates 2-5psi while maintaining constant throttle under load, and every time the boost drops a small amount of smoke appears.

Any insight on this problem would be appreciated.
Thankyou

[SHEIDEN9]

I recently had the same problem it turned out to be the wastegate selonoid.Also check the hard plastic vacuum lines that run to the wastegate they like to break under the intake. i hope this helps.

[Ray Sharpe]

That is one of the things I checked for, but there is lots of vacuum at the wastegate, and I still have the wastegate wired shut. The computer sent out code p0236 (Manifold pressure out of range) Which is why I replaced the MAP sensor. This got rid of the code problem, and helped with power some, but it still seems a bit doggish. Could the manifold temp. sensor cause this problem? I'm going to try disconnecting the battery and reseting the PCM. :confused: I haven't hooked on to anything heavy since that long trip either, so maybe the code will come back with some extra weight on the back.
I was thinking at one point that my Turbo might be pooched but it doesn't blow out any oil, and there is no more play in the shaft now than when I bought it.

Anyway, still chugging along. Thanks for the input.

[DennisG01]

Had the same thing about 2 weeks ago - loss of power, lot's of black smoke. Definitely noticed loss of power while pulling, not so much when unloaded. Turned out to be a sticky wastegate solenoid and some small holes in the crossover pipe. I think the holes where the main culprit.

[Ray Sharpe]

I don't think it is the crossover pipe. It looks like brand new.

[DA BIG ONE]

I had the same issues, turned out to be failure to the boost control circuit in the ecm. Manual boost controller fixed it, and it has never run better than now!

[Ray Sharpe]

That sounds interesting. But I've had the wastegate wired shut for a while now, so I don't see this being the problem. Is there a major danger in tieing off the wastegate? My boost doesn't act much different, it just stays a little higher for longer duration. But it never goes over 12 psi anytime.

[rjwest]

Sounds like a " defuel " condition was set in PCM,

If boost or temps to high, sets defuel condition,
will not set code,,,,,
will fix it self with Ign off cycle.

Install mech boost controller, get above 9 psi
and 180 degrees ( approxmate ) and defuel occurs,

Read codes with laptop, no codes set, do clear codes
and power restored.....