'98 K2500 surging at idle, can't figure it out

[JLeather]

Here's the sonnax kit for the leaking boost valve:

https://www.sonnax.com/parts/1985-boost-valve-kit

and attached is the service bulletin I found with the additional info about drilling the passage.

 

[east302]

Thanks for updating, hope this is the fix for it.


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[JLeather]

So I didn't feel like laying on my back pulling a trans again. I bought a used 2 post lift a couple years ago and kept putting off installing it because I thought it was going to be a pain, but this was good motivation. Lift is up, truck is up. I spent 4 hours the first day getting the stupid exhaust pipe off. Broke all 3 bolts at the cat, but didn't break any of the manifold bolts! More to follow...

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[JLeather]

Just this past Friday I finally got the truck buttoned back up. I took care of a number of things while the trans was out including the rear main, oil pan gasket, trans input/output seals, t-case output seal, new exhaust gaskets at the CAT and the manifold, new trans cooler fittings, etc. The trans internals got the Sonnax boost valve and line/lube kits in the pump, plus a new EPC solenoid and I drilled the case for the leak pressure to vent. That also meant new valve body and accumulator gaskets. But I can say that the reverse issue is gone (so far anyway). I've put about 100 miles on the truck and it hasn't had any issues with surging. It was a lot more work than I expected, but I would do it again. I only have about $250 in the repair. The pump wasn't the best inside, but makes spec-pressure and as little as I'll probably drive this thing I expect it to last a good many more years now. I did not to any clutches, and I only saw 4th (which looked great BTW) because it came out with the pump shaft.

 

[Panner99]

Just this past Friday I finally got the truck buttoned back up. I took care of a number of things while the trans was out including the rear main, oil pan gasket, trans input/output seals, t-case output seal, new exhaust gaskets at the CAT and the manifold, new trans cooler fittings, etc. The trans internals got the Sonnax boost valve and line/lube kits in the pump, plus a new EPC solenoid and I drilled the case for the leak pressure to vent. That also meant new valve body and accumulator gaskets. But I can say that the reverse issue is gone (so far anyway). I've put about 100 miles on the truck and it hasn't had any issues with surging. It was a lot more work than I expected, but I would do it again. I only have about $250 in the repair. The pump wasn't the best inside, but makes spec-pressure and as little as I'll probably drive this thing I expect it to last a good many more years now. I did not to any clutches, and I only saw 4th (which looked great BTW) because it came out with the pump shaft.

I'm having the same problem in my 1999 Escalade. When its hot or warm out it surges at idle, but when in park. Difference is my escalade has the 4L60E not the 80 or 85. I replaced EGR, IAC, PVC, wires, cap, rotor, plugs. Cleaned the MAF and the throttle body. It has the upgraded injectors.

I'm running out of ideas.

 

[big_mike]

I'm having the same problem in my 1999 Escalade. When its hot or warm out it surges at idle, but when in park. Difference is my escalade has the 4L60E not the 80 or 85. I replaced EGR, IAC, PVC, wires, cap, rotor, plugs. Cleaned the MAF and the throttle body. It has the upgraded injectors.

I'm running out of ideas.

Have you checked the fuel pressure?

 

[JLeather]

I'm having the same problem in my 1999 Escalade. When its hot or warm out it surges at idle, but when in park. Difference is my escalade has the 4L60E not the 80 or 85. I replaced EGR, IAC, PVC, wires, cap, rotor, plugs. Cleaned the MAF and the throttle body. It has the upgraded injectors.

I'm running out of ideas.

From what I read the 4L60E can have the same problem I did. If you want to confirm it's a transmission issue you need to do a line pressure test when the issue is occurring (so warmed up, in reverse). When I revved mine up in reverse the line pressure became excessive and erratic. I bought an OTC gauge on Amazon for like $50 and did it myself, but I will say that you pretty much need a lift to get to the port. It's behind the neutral switch and you need to temporarily unplug the switch and install a 1/8" NPT elbow.

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[Panner99]

I did check fuel pressure. It is good. No issues.

Reverse doesnt affect my idle. Its usually after I drove for a bit and it does it in park. Also has to be hot out. All winter it doesnt rev at idle.

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