What engine?

 

4.0 engine

 

Any CEL trouble codes yet?

Rough idle on these 4.0s can be caused by a lot of things.
First off the basics; new air filter, PCV valve, spark plug wires if applicable and check for vacuum leaks.
On some 4.0 intake manifolds there's an unused vacuum nipple sealed with a rubber cap.
It must of deteriorated and fell off my 4.0 causing erratic idling and other problems.

The Idle Air Control valve (IAC) is notorious for causing a rough idle when dirty or defective.
The IAC can be disassembled and cleaned carefully in addition to the throttle body.
There's some Utube videos on how.
I clean mine about every 50K miles.
Some others; dirty or defective MAP sensor or O2 sensor.

Clogged or leaky fuel injectors. Might try injector cleaner additives and see if that makes a difference over time.
I'd also start using top tier gas if not already.

Far as the oil gauge pegging, if all the other gauges are working my bet is a bad oil psi sensor, easy to change.
Or its connector got loose, corroded or has spread pins.

 

I dont' have a code reader and it wouldn't stay running long enough to drive to town (12 miles). Seems odd that the oil gage would go bonkers at the exact same time the engine starting acting up.

The wife called yesterday morning to say the car was acting up about a mile from the house (more so than just the ruff idle which had been going on for about a week). When I got home, I started it and drove it up & down the street & besides the oil pressure gage, it wasn't all that bad, so we decided to take it to town to have the codes checked. When we re-started it, it would die within a few seconds and not re-start. If I let it set a few minutes, it would re-start, but run for long.

 

Thanks for all the advice. Two things made it run better...1), cleaned the throttle body and the AIC....and 2) put the plug boot onto cylinder 6....I somehow managed to not get it onto the plug when I changed them the other day (I heard the loud snapping as the clue when I started it after cleaning the AIC).

 

Thanks for the followup.