98 4L Explorer idle miss

[billwatr]

Missing on 2 cylinders while idling....Seems ok when under load, lots of power and smooth.
New plugs, wires, crank sensor and motor-vaced(sp?).
Any suggestions??
Thanks, Bill

[shorod]

Welcome to the forum!

How did you verify that it is missing on two cylinders, by the diagnostic codes or by physical checkout? Which two cylinders is it missing on? If the two missing cylinders share a common coil pack, you may have a coil pack issue.

When was the last time the fuel filter was changed? Have you added a bottle of fuel injector cleaner to the tank recently?

-Rod

[billwatr]

The mechanic determined it by codes and physically. I don't know which cylinders. He figured it was not the coil pack, but admits he can't pin it on any thing else.
Have not checked the fuel filter, but would that not effect running with a load on too?
Recently did run cleaner through and also moto vaced the engine.
Thanks, Bill

[shorod]

Well, a restricted fuel filter would probably be more likely to cause an issue under load, but it seems like fuel filters, cooling system flush, brake fluid, and transmission service are a few (of many) often neglected routine maintenance items.

Keep in mind that a "misfire" could be due to fuel, spark, or compression issues. Without knowing which two cylinders are missing, and what was performed to "physically" determine the misfire, it's difficult to offer much guidance.

I'm not very familiar with the moto-vac process to understand if that involves de-carbonization of the valves and pistons. If so, that is a good piece of data.

Did this misfire happen to occur shortly after the new plugs and plug wires? Maybe two of the wires are not fully engaged and making intermittant connection.

-Rod

[billwatr]

Good Morning, Compression is good for all cylinders.
Yes, the moto-vac process is de-carbonizationization.
The "missing" just started one day...that's the reason plugs, wires, moto-vacing, etc. was initiated.
Thanks, Bill

[shorod]

Hmmm, about the next thing I can suggest is to find a scan tool with the datastream mode and monitor the voltage of the sensor 1 oxygen sensors. See if they seem to be switching properly, or if they spend more time in the "lean" or "rich" range. If so, post back and that will guide us in a "fuel" or "spark" direction.

-Rod