it has a missing cylinder when the RPMs are low. Idles like a diesel truck, but is smooth on the highway. It started about halfway to Detroit, and got progressively worse. However, I at least made it back into town fine, even if stoplights were terrifying.
I figured the problem was a confluence of a few things - first, the somewhat leaking valve cover gasket is now very much leaking. 1700 miles loaded heavy, pushing hard on the highway through summer heat will do it I suppose. I used (or more likely, lost) about 2.5 quarts of oil on the trip. Much of this is now clinging to the engine all over the place. There was oil grunge all over the spark plug wells, so next I figured it was causing the miss somehow.
That's *after* cleaning - there's still grunge everywhere.
I took the plugs out and cleaned the whole area. I had new NGK plugs and Bosch wires ready to go, so figured it was as good of a time as any to replace all of it (both are original-to-me equipment).
That did not fix the idle miss, but it sure as hell sounds way better otherwise!
The old #3 plug's connector showed far more oxidation:
...so perhaps #3 is running lean due to a clogged injector? Barely anything at idle so it feels like a miss, not enough at higher loads but enough to pretend to get by?
At least now the top and hot side of the engine is much cleaner so I can observe for where the valve cover gasket might be leaking from. Pretty sure it's the chief contributor since the lower rim of it was very wet with oil grunge.
Any other hypotheses for "idles steadily but poorly, but no discernible trouble at street/highway speed"?
