Surging '89 K1500

[Kyle C]

My truck surges slightly at highway speeds. It's been doing it for a couple of years but after several $ spent with no luck I decided to live with it. The dollars were spent on fuel filter, plugs, cap, rotor and wires that I installed with no effect on the problem. The dealership then replaced the fuel filter, egr valve and cleaned the injectors and again no joy. Anyone have any ideas on what else I might try replacing. It has a 5.7 motor.

[Shawn T]

My truck surges slightly at highway speeds.  It's been doing it for a couple of years but after several $ spent with no luck I decided to live with it.  The dollars were spent on fuel filter, plugs, cap, rotor and wires that I installed with no effect on the problem.  The dealership then replaced the fuel filter, egr valve and cleaned the injectors and again no joy.  Anyone have any ideas on what else I might try replacing.  It has a 5.7 motor.

 

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My father had the same problem with his 89 5.7 and we(including mechanics) could never remedy the problem(no codes). After about 10,000 miles of this he decided to just start adding fuel addatives and injector cleaners to every fill up. It took about five tanks of gas and it has ran like a charm ever since. I guess it was a choked fuel line or a slightly clogged injecter nozzle. Who knows? The throttle bodies are easy to visually check. Just make sure the injectors are spraying a fine mist. I am no expert but sometimes it seems like it is the stupidest, simplest things. Good luck.

[Peter_C]

You could try plugging off the EGR valve and driving it to see if it makes a difference. Sometimes a lazy 02 can cause this type of problem, as can a vacuum leak. Never hurts to replace the throttle body base gasket if it has not been done in the last 5 years.