I have a 1988 Chevy C3500 1 ton PU. Engine runs great at idle and acceleration but when cruising it runs rough or surges.

Surges under load but only while going uphill Page1 - Chevy High ...

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Mar 6, 2011 - 14 posts - ‎8 authors
Trying to help out a friend. ... The truck starts, runs, and drives fine until you get to a hill. When going up hill it begins to surge, almost stalling but not quite. ... rubber fuel lines suck shut under a heavy load and act like that. .... tranny fluid level o.k.? ya got me stumped. runs great when it's on a flat surface?

Ford 460 engine - RV mechanic

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Will not take gas going up a hill but will maintain speed at 55 mph. ... Want to do a diagnostic test on my 1997 F250 with 460 engine. ... only get to about 40 miles an hour if i push it the engine acts like its running out of gas,thank you .... The truck hesitates on acceleration, while driving on flat surface is fine, however climbing ...

rough idle, stalling, loss of power. - CarGurus

Could be a vac leak, a dirty throttle body plate, or a faulty idle air control valve.

Could be a dirty throttle body or faulty idle air control valve.
Is the check engine light on ?

I Have a couple of questions. First question does engine surge when idleing cold? 2. Does engine start quickly without a lot of cranking, Cold or warm? 3. Do you have funny smell at highway speed, or after you stop? With out this info and your imput, I would only be guessing. I am retired mechanic of 25 years. and would like to help if u need me.

You can remove the egr and see if it has been sealing,and if it still moves.

Sounds like you could have gotten some water in your fuel tank from that fill up. Go to a autoparts store and get a product to put in the tank that takes care of water in fuel. Use it when you fill the tank up a few times after and hopefully it goes away. Whenever you can't sustain power in the engine or it runs rough then your cruise control will constantly be shut off because the engine doesn't have the power to keep the speed up and should go away once your engine is running clean again.

Good Luck

Make sure all the glow plugs are working.

Check your EGR valve make sure that is working properly, if it is then go to the fuel pump, just a cheaper fix to go after the EGR then the fuel pump

Sounds like a possible vaccume hose leak?