98 yukon, Oil on cylinder #1 Spark plug..?

[Eman85]

Right below the oil fill tube, buy a matching plug and clean the area good.

 

[OilBurner2003]

Just remember that you can have good compression and still get an oil fouled plug.

I have a symptom I've never seen before. Very rough idle with some misfires, as soon as you get over 40 MPH all misfires go away...? I swear, this truck throws everything under the sun at me. May be making a call to previous Mechanic.

 

[OilBurner2003]

Right below the oil fill tube, buy a matching plug and clean the area good.

Pulled the plug today, that's actually exactly what I did. Had oil on it. Didn't have time for a compression test, but I'm sure there's something along the lines of either a valve or something else. Will see if I can do it in the morning.

 

[OR VietVet]

I have a symptom I've never seen before. Very rough idle with some misfires, as soon as you get over 40 MPH all misfires go away...? I swear, this truck throws everything under the sun at me. May be making a call to previous Mechanic.

Sometimes, when you have misfires that seem to go away at higher rpm's, there is a vacuum leak or a fuel feed problem.

 

[OilBurner2003]

Sometimes, when you have misfires that seem to go away at higher rpm's, there is a vacuum leak or a fuel feed problem.

Even though the Injectors and DELPHI Pump are brand new, I've always wondered at this point if I should put a FP gauge while driving. It's supposed to be above 55 PSI or close to it, correct?

 

[OR VietVet]

Yes, but what is the readings at idle and slight throttle, that I assume is where your misfires are happening, correct?

 

[OilBurner2003]

Yes, but what is the readings at idle and slight throttle, that I assume is where your misfires are happening, correct?

Last I checked, FP was 55 at idle, I believe slight throttle was maybe 54/55. I should hook up the gauge again and see what it give's me now.