04JeepGrandCherokee

Not sure what the problem is but when im at a stop light it will slowly drop from 700 to 550 RPM's. not a huge difference i know but is this normal or could it be that i need to clean my IAC or TPS? Thanks for the help

candymancan

Good question, i have a 98 grand cherokee with the inline 6 and i noticed mine on startup sits around 700-750rpm, and after maybe 5 minutes it goes down around 550-600 Rpm, when i drive it around and stop at a stop light the engine will idle around 650-700RPM and then after maybe 10 seconds will go down to 550RPM and stay there.

I do notice the Jeep seems to have more vibration in it when the RPM's go down. When its around 650-700 its fine but once its down to 550 or so the Jeep starts to vibrate more.

I dont know if this is normal because i just started driving cars recently, and even tho this Jeep has been in the family for 10 years now, now that i am actually driving it im trying to figure out if 30 PSI idle oil pressure is normal and the RPM's are normal or not.

I always thought normal RPPM's were suppose to be around 700 not 550, I did the Jeeps tune up myself, replacing the plugs, cables, distributor cap, rotar, replaced the oil, air filter ect but it doesnt seem any of that changed anything.

Im thinking maybe the Jeep needs cleaning with some seafoam or something, as when i replaced the old spark plugs i noticed the old ones had alot of carbon buildup. I have a friend who seafoamed his Jeep through the throttle body and after he did that the thing Idle'd at higher RPM's and the oil pressure went back up.. So maybe thats what we need to do ? Probably so much crap in the engine after the 160k miles mine has that it needs a good cleaning

04JeepGrandCherokee

i was also thinking about going the seafoam route. another thing that i thought about today is maybe i need a new fuel filter. it might be clogged up a little bit causing a drop in the amount of fuel getting to the engine

TONY-IN-SO.KY

Not being a raincloud or worry-wart, and I don't know how mechanically inclined you fellas are, but maybe drop oil pan and make sure oil pump is not clogged. I've got a 96 laredo w/4.0. I got it for my wife. When I bought it I was completely green about a Jeep. Shortly after we had it, we began experiencing idle issues, shortly after that the motor developed a sort of whine (like the sound of crank bearings getting burned up. Got a rebuilt motor for $900 + $200 for 100,000 mi. warranty. All things considered, i wish someone would have told me to periodically drop the oil pan and clean out the oil pump, not that hard, and can be done for under $150 if you need new pump and gasket...? It is REAL messy though.

04JeepGrandCherokee

hmm couldnt hurt to take a look.. ill give it a try when i get the chance