1996 K2500 runs rough

[Will L.]

99% sucky
1% good is you are sure what the problem is.

 

[Husker6.5]

My IP on the 98 Burb was/is doing the same thing, uneven idle, 200+ rpm surges at a steady throttle, and runaway incursions to the red zone on the tach when you "blip" the throttle pedal. The 200 rpm surging is what took out the transmission, lost the TCC, OD and 3rd gear all at the same time on the Interstate when it dropped out of OD to 2nd at 75mph! Limped it home at 45mph in 2nd gear.

 

[chevyCowboy]

My IP on the 98 Burb was/is doing the same thing, uneven idle, 200+ rpm surges at a steady throttle, and runaway incursions to the red zone on the tach when you "blip" the throttle pedal. The 200 rpm surging is what took out the transmission, lost the TCC, OD and 3rd gear all at the same time on the Interstate when it dropped out of OD to 2nd at 75mph! Limped it home at 45mph in 2nd gear.

This truck has had 3 nv4500 from the pump surging

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[79jasper]

Well he decided to go the pump swap route.
Runs better than when he bought it.

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[chevyCowboy]

Glad you figured it out

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[79jasper]

Yup.
Already had a boost gauge.
We added oil psi, coolant temp, and a voltmeter.

Next will be looking into some wiring under the dash. When you use anything electrical, the dash lights dim way down and the stock voltmeter drops.
I'm thinking a bad ground.

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[Husker6.5]

There are no bad grounds, only misguided ones.

 

[79jasper]

Lol good point.
Crappie weather, so might be awhile.
It's odd, with the lights on bright, the drivers light will dim with window use. On dim, both will flicker.

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[jrsavoie]

"I also noticed the FSS is leaking."
This can be the source of air. As mentioned eliminate air by the clear return line check as step #1 and then and only then step #2 is trons: grounds, filter harness removal etc. Grounds are always good advice, but, air free fuel is step one.

Not really a step 1 and 2 there. Kind of a both step one type of deal.

Also check for vacuum. It's easy and fast of you start the truck and the actuator on the turbo is stiff, that is good to go.

It only takes a minute to pull the vacuum line off the wastegate solenoid to check the actual vacuum before and after the solenoid.

 

[WarWagon]

Not really a step 1 and 2 there. Kind of a both step one type of deal.

Also check for vacuum. It's easy and fast of you start the truck and the actuator on the turbo is stiff, that is good to go.

It only takes a minute to pull the vacuum line off the wastegate solenoid to check the actual vacuum before and after the solenoid.

Depends on how one goes about things. Both are very important on these trucks, but, IMO one has to stay focused on one thing at a time and if you have to choose GM says start with air and fuel flow first. Cleaning grounds is simple enough, but, further into trons, electronics, is very difficult for most. So my second suggestion is screw up one thing at a time: don't break off a ground wire as you put it back together while fixing a fuel system problem and then spend the next two days overlooking an area you keep ignoring thinking you fixed it. Air leaks in a system is bad enough to fix as it is. Even with multiple problems: one thing at a time.

 

[79jasper]

He's been driving it for about a week now, pretty happy with it.


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