Engine Low Idle?

I have a 1987 Jeep Cherokee 4.0L with 130k miles.

It has an odd idle issue that I will do my best to describe. Note that I have checked the distributor cap, cleaned the throttle body and I think I have checked the vacuum system pretty thoroughly, but I am not an expert in cars by any means.

First of all, for the first 5 minutes or so of driving, the idle drops really low when put into N, to under 200 RPM. It instantly recovers and then runs at about 700 or 800 RPM. After 5 minutes of driving, it stops doing this. This happens every time I drive it.

Secondly, When accelerating, once in a while the RPMs instantly drop for a split second. This creates a strong****** motion in the jeep. It seems to be most likely to happen when the road is bumpy but that could just be a coincidence.

After that happens, the Jeep runs fine except if I put it into N, sometimes it will die instantly for a minute. Sometimes it is also hard to start the jeep back up if it dies this way too. It seems like I have to wait a minute or two before it will start.

Sometimes, after this type of issue, the RPMs will run very high for a few minutes when in N, somewhere around 1500 RPMs. After a few minutes, the RPMs return to normal

The problem is very occasional. Sometimes I can drive all day without it happening once and other times it happens every 5 minutes.

Thanks for reading, any thoughts?

Thanks alot, I'll give those ideas a try.

I have a 1997 jeep grand cherokee 5.2 v8. It idles low about 500rpms and sometimes it will stall when you come to a stop but will always start back. Also if I fill up completely with gas it will smell of gas and leak out some on the ground. The smell and leaking is not present from 3/4 tank to empty. Any ideas would help me alot thanks.

I have a really crazy problem with my 96 cherokee automatic idling low. I have changed the air idle control, TPS, Both oxy sensors, new battery, Plugs, wires, cap rotor, new battery/gnd cables, new cat & exhaust, cleaned and checked throttle body, no vaccum leaks ican detect, charging good. I do have a crack inthe exhaust manifold dealer tells me but not bad. Checked map sensor ok I think but did not change. Jeep will start up and idle fine (750)when cold but after driving for 10-20 minutes the idle drops to 250-200 at stoplights. Or under and sometimes stalls at stoplights. When stalls Starts right back up. Weird thing to me and very telling is if I disconnect neg cable for a few minutes. Jeep will idle fine for a day but next day low idle problem will return. Jeep runs great and good power & oil pressure. I am at my wits end and this is my wifes daily driver and shes gonna get rearended I gotta get this fixed. I am pretty good backyard mechanic but this one is tough. Anybody got any ideas or experiences? Any help much appreciated

I have an occasional problem where my Cherokee sometimes dies at idle or almost dies. Every now and then it bogs going down the road. I am almost lost here and I am not a car idiot. I have replaced a distributor, fuel pump, fuel filter and coil very recently. Within the last couple years I have replaced the map, Iac, Tbs, brain box, crank sensor, ignition switch, and just about everything else electrical as well. The problem happens at no specific time. At idle long enough it starts to miss and sometimes dies. But usually seems to start back up easily. Just yesturday my wife took it out to get gas and 2 minutes later dead. I eventually got it started by purging the fuel line a couple times and it fired up. I am thinking the fuel regulator which I cant find anywhere. No lights ever come up when it happens. There were old codes saying coil, o2 sensor which were replaced. This is my third coil and second fuel pump. PLEASE HELP I am starting to lose my mind.

Actually my 96 doesnt have the fuel regulator on the fuel rail, mine unfortunately is in the tank. I am pretty sure there isnt a return line as well. Last night before I asked for help I removed the rail to blow out the fuel line all the way back and tried cleaning the injectors on the outside. Speaking of relays about a year ago it stalled and woundnt start and found out the fuel relay blew out. I replaced it for my wife and a mile down the street it blew again and replaced it with one out of my 99 and drove it home. Since then no more blown relays for the fuel. At that time I replaced the fuel pump the first time. I dont really think the problem is relay related. Just the other day iI purged the fuel line and it fired up to get it home as quick as possible. Is it it possible that the fuel relay is wired to the fuel regulator. If the regulator sometimes hickups I could see how that could heat up the relay. Does the ignition coil and o2 sensor share a common wire with the regulator? Those Chiltons and Haynes only tell basic stuff and never tell you really how to test things. Thank you for your help it is very appreciated.

The 8th digit is an S and it is a sport. Thanks for the quick reply.

My email is kimmielz1@hotmail. Com
Thank you for the info and I'll get back to you tonight.

Looking forward to youe E-mail. As of now I cant even get the fuel pump to prime.

Well I have spark.

Hi there, lately I have been having problems with my 1994 Jeep Grand Cherokee, 4 liter. Sometimes when I come to a light the rpms drop really low like I am going to stall. It doesn’t stall but it feels like its coming.

I can reproduce the symptoms by holding my foot on the brake and slightly tapping the accelerator, when the Rpms jump up they immediately fall really low like around 200. I have done some things to try and help, first I have:

1. Ran good gas through, with fuel injector cleaner
2. Changed the oil
3. Cleaned the throttle body.
4. Tested the battery Passed
5. Tested the alternator which failed with my little tester, is shows that there is something wrong with my alternator, it shows in the red, but barely. Everything still works the lights aren’t dim or anything.....

So could the alternator be causing my problems? Or something else? Any ideas. I am thinking of changing the fuel filter.

Thanks for your ideas.

I would suggest looking for a vacuum leak. If your exhaust isn't too loud, you can hear it as a hissing noise when the motor is running.