Hey y'all;
I've got one of those "mystery problems," could use some help. I drive
98 Cherokee Sport, 4.0L inline 6, with manual transmission, around 110K miles. The problem I have is this: at about 2000 RPM, the engine loses power and sometimes misses. During the latter incidents, it acts as though its not getting enough fuel, something like the beginnings of a fuel pump dying but not as severe. The problem is more pronounced if under load (AC on, carrying heavy stuff, going uphill..) or in higher gear ranges, and seems to be worse when the outside air temperature changes rapidly. Gas mileage has dropped by about 5-6 mpg since the problem started.So far, several visits to the dealership have been fruitless. There are no codes being generated, so there's not much to go on. The oxygen sensor was replaced a few months before the current issue started due to a different problem, and the throttle body & connections thoroughly cleaned then, too. The dealership tried to tell me I had "weak valve springs" and needed a complete engine overhaul ($800+) to replace them, which did not sound right to me at all. I've had a lot of trouble finding a good garage nearby, so I'm ready to start tinkering myself in what little spare time I have. :-(
I've seen a lot of stuff on here about bad TPS sensors and/or bad connections, could this be the cause of my problem, too? I don't have a big toolkit nor am I terribly knowledgeable about fuel systems or testing voltages and such, so I'm not sure how best for me to start working with this. I bought a Haynes Manual a long time ago, but it doesn't have much info in it about sensors & such for the 1998 model (& newer).
Also, just recently, it has started with a new problem: when I turn on the left turn signal, both lights blink as though I'd turned on the hazards. Doesn't happen with the right blinker, doesn't happen if the ignition is off and the car parked, only when running & in motion. Almost simultaneously, the rear passenger electric door lock mechanism began malfunctioning, and refusing to lock or unlock while making a nasty grinding noise. I have no idea if these problems could be related in any way (grounds gone bad? shorts? lightning? ) but I just wanted to mention them in case they are clues.
Thanks for whatever help you can offer.