Yukon Misfire At Highway Speeds

[olin6501]

I have a misfire on my 1997 Yukon 5.7L only felt at highway speeds when barely on the throttle. When towing a boat the misfire is not felt.

 

I have replaced the plugs, wires, cap and rotor. Coil is next but is there anything else I should look at.

 

-Josh

[pennzoil29]

It could possibly be the coil. Have you changed the fuel filter? Did you make sure the new plugs were gapped properly, and change the wires? Dirty fuel injectors can cause this also. Just a few things to consider. Hope you figure it out.

[95Sierra2500]

I would lean toward the fuel injectors. I had a similar problem with my wife's Jimmy. The poppet nozzles tend to stick closed, but for some reason it's only noticable at highway speeds with no load. See if your local dealer will run a top engine clean on it. That should take care of it.