Jeep acting strange, desperate for advice.
Hi everybody, this is my first thread, be gentle!
I'm more or less mechanically inclined, a small engine mechanic actually, not a vehicle mechanic yet, but learning as I go.
I have a '99 WJ, inline six, selec trac, 148 thousand miles.
My oil pressure usually rides around 40 idling, and 55-60 while moving.
Lately, once the engine warms up, the oil pressure drops to around 19-30 when idling and no more than 40-50 when moving. It's accompanied by an barely perceptible erratic "shiver" when idling at the low oil pressure, when moving it seems to have lost a little bit of its power, and noticeable shifting hesitation. there's a very rich almost propane-like, or "chemically" exhaust smell (but not quite like a cat converter rotten egg smell) along with abysmal fuel milage. When coasting along after a complete stop, it idles roughly and has trouble coasting smoothly.
No codes or engine light so far. RPMs seem fine.
Oil looks fine (but high time to change) and at normal level, using wix filter, tranny fluid good, coolant at proper levels. No leaks besides the tiny age-old tranny pan leak which I've kept up on.
I'm wracking my brain on what it could be. Thinking maybe clogged oil filter, bad oil sending unit, or clogged fuel injector, but any one of those wouldn't cause all those symptoms would it? I keep wondering if it's the exhaust valves, but I tested the exhaust pressure and there's no obvious back-suction.
You guys and gals have seen it all when it comes to Jeeps, what's your educated guess?