low power surging throttle

[Fossilfreefuel]

Hi posting for my friend/customer.

Vehicle in question is a 98 Suburban 6.5L

When highway driving could not bring the vehicle past 55 (towing a couple hundred pounds in a 4x6 trailer). Drove 3 hours then after 8 hours drove 3 hours back with the same load. Same low power scenario and then, while driving, the throttle would surge out of control intermittently.


I started the vehicle the next day and drove around town. Went up some very steep hills and had full power, no surges or power loss.

One note, the 4x6 trailer had some funky wiring that blew the turn signal and hazard fuses. Probably unrelated but since this whole problem seems electrical I might as well mention it. Also, has a remote mounted PMD on the bumper with heat sink.

PMD?
Crank Position Sensor?
ECU?
IP?

Advice appreciated.

Thanks

[Fossilfreefuel]

and for codes I have P0236- turbo out of range
and P0251- IP metering control

[Fossilfreefuel]

I think the low power was a vacuum issue. The wastegate solenoid is being intermittent. It will work, and if I unplug the line onto the wastegate and put it back on, it will not work. Then if I disconnect the vac source from the solenoid and plug it back in it will work again sometimes. I took the piece off and tried to clean it but it didn't seem to be too serviceable. The wiring harness to the solenoid seems fine and works consistently.

Should I just replace that piece? Is that a dealer only part?

[JohnC]

Wastegate solenoid failure is not uncommon. they should be available from other than the dealer, but you won't save much.

Verify the vacuum to the solenoid is steady and at least 20". Verify the vacuum pump is connected to the solenoid port with the restrictor. Verify the wastegate actuator and associated plumbing does not leak. check the vacuum at idle to the actuator. It should be about 14" and steady. If everything else checks out, replace the solenoid.

[fire846.2L]

wow, this sounds like the issue I am having with my 6.2 non turbo.
Any ideas on this one? I am searching this thread as this is my first diesel and really want to get it working correctly.
84 3/4 4x4 6.2L
Thanks

[JohnC]

wow, this sounds like the issue I am having with my 6.2 non turbo.
Any ideas on this one?

Basic rule of Diesel ownership: Verify the fuel is clean, the fuel filter is clean, the air filter is clean, and the injection pump has a good supply of fuel.

If a Diesel has air, compression, (heat) and fuel at the right time, it'll run fine.

[Fossilfreefuel]

That last statement is true..... if there are no electronics involved

[JohnC]

Even if there are. Fuel, at the right time...