Jeep Grand Cherokee stalling - HELP!

[FlyingJ 0]

Hi everyone,

Having an issue with my 96 Jeep Grand Cherokee (5.2L V8). I'm on a 24 hour shift at work and spending any down time trouble shooting with plans to take it to the dealer in the morning if I haven't gotten it running by then.

Here's the deal...

It's been idling funny. Not sure how to describe it other than to say it is a "bounding" or "bouncing" idle, going from 2-300 up to 800-1000rpm and bouncing up and down. This doesn't always happen and I have had it happen first thing in the morning as well as after I've been driving all day. Most often it "bounces" but does not stall. Sometimes it goes so low it barely hangs on or eventually stalls.

It's also been stalling, hot or cold, always as I am coming to a stop. It happens 3 or 4 times in my 4 mile ride to work first thing in the morning at 40 degrees and happens at the end of a 35 mile drive at 70 degrees outside. Sometimes it happens consistently, other times it doesn't happen for days.

I've changed the plugs/wires/cap, PCV valve, fuel filter and IAC motor and ensured the throttle body is clean (PCM was replaced two years ago). No change with the first two. I did the fuel filter and IAC motor this evening. It seemed to be idling much more steady than normal for a while. Started it back up and let it idle while I was trying to listen for an obvious vacuum leak. I can't find any obvious (it would have to be SUPER obvious as I really am pretty clueless) leaks. While looking for leaks the idle began "bouncing" again, did it for about a minute and then stalled. Now the car starts and will run for about 5 seconds before stalling. The throttle body gasket appears good and again no SUPER obvious vacuum hose leaks, but I do not have the ability to pressure test. I do have a code reader but no codes have been thrown.

Just working through all of the suggestions in my Hayne's manual, everything keeps pointing to a vacuum leak somewhere. I really do miss the "Bently Bible" manual I had for my old Volvo 240. With that book in hand I used to feel like I could do anything.

Any suggestions are appreciated. Like I said, I'm at work here until 9am and have two hours off before I'm supposed to be at my part time job. Hopefully the good citizens of my county will forget the number for 911 this evening and I'll just keep plugging away until it will run or it's hooked up to a tow truck and on the way to the shop.

Much appreciated!
Jason

EDIT TO ADD: http://www.youtube.com/watch?v=RqL8hn0SRFs

Here's a video of the idle "bouncing" I mention. This is about normal, but the range of the bounce is anywhere from 1,000rpm down to just barely staying running.

Killing threads since 2004.

[theonlyski 8]

I would think it might be a vacuum leak, or an intake leak. You didn't say you changed your air filter, that might have an effect on it if its all clogged up.

I do highly recommend a seafoam treatment... I did it on my 03 silverado (5.3l v-8) with about 103k miles and it blew alot of that crap out, ran a little peppier after that. Its been known to help idling issues. Also, check your mass air flow sensor.

Good luck man!

"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

[FlyingJ 0]

Thanks for the input. Forgot to mention the air filter and sea foam, but those are both part of my regular maintenance. I spend a significant amount of time driving on the beach as well as very dirty ranch roads and change the air filter at least every other month, if not monthly. I use Sea foam regularly as well.

Started right up this morning and ran just fine for several laps around my work parking lot but ended up stalling as I came to park and then started doing the "bouncing" idle again.

At this point I'm just happy it stayed running enough to drive it to the dealer instead of having it towed 45 miles.

Killing threads since 2004.

[KJM 0]

Hi, it definatly sounds like a vacuum leak. Have you recently serviced your transmission? Sometimes when you change the tranny filter you can get a tiny leak that is really hard to detect but will make your car run just the way yours does. I used to have an old wagoneer and had the same problem a couple of times.

[tkhayes 348]

hey its Saturday morning, you should be calling 1-888-CARTALK

[freethefly 6]

Doesn't sound like a vacuum leak problem as a vacuum leak usually just cause an engine to idle rough, unless the leak is so great that it interrupts the pull of the charge through the intake. I would take a look at the fuel pump.

"...And once you're gone, you can't come back
When you're out of the blue and into the black."
Neil Young

[warpedskydiver 0]

It is the sensor for mixture O2/fuel, it controls idle mixture.

You should get some very good injector cleaner and put that through the tank.

You can get an online step by step instruction manual to help you do this.

As a last resort the sensor will need replacing, but it does not help to do that first, because everything in there is covered in varnish by now.

I have a 1995 Grand Cherokee.

The other thing it could be is that your injectors are getting very dirty or malfunctioning.

If they need replacing GB makes an entire set for what you would pay for just two.

I already had to do that.

Take it to autozone and put the scanner on it

The injectors are so easy to replace even a skydiver can do it. j/k

Takeoff on the caveman commercial

[warpedskydiver 0]

My jeep did the same thing, the O2 was only dirty but I had one bad and one intermittent injector.

Because the O2 sensor is dirty it thinks the mixture is too rich, so it leans out the mixture at an idle you would really notice as it would surge and wane.

[warpedskydiver 0]

If you ever wreck the front bumper cover they make a really nice all aluminum version for off-roading, no more tearing it or cracks, small saplings will be like weeds.

[freethefly 6]

Before throwing parts at it, hoping for a cure, I would get out my digital multimeter and get value readings on the components in question. Following the trouble shoot flow chart will lead you to the cause of the problem and save you from frustration and wasting money.

"...And once you're gone, you can't come back
When you're out of the blue and into the black."
Neil Young

[sundevil777 102]

Quote

If they need replacing GB makes an entire set for what you would pay for just two.

What is "GB"?

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[airdvr 210]

Surging is caused by a lean condition. Look for what controls the fuel mixture. MAF sensor is a good start but there are many sensors. Is the check engine light on?

Please don't dent the planet.

Destinations by Roxanne

[warpedskydiver 0]

Quote

Quote

If they need replacing GB makes an entire set for what you would pay for just two.

What is "GB"?

A brand of injectors

[FlyingJ 0]

Thank you all for the suggestions. At this point the Jeep is at the dealer. I really am a somewhat adequate parts changer at best, though I'm trying to learn what I can here and there. I am hoping within the confines of the initial diagnostic fee they can pin point the problem and from there I can decide whether it is something I can do on my own, take to my local mechanic (who is a much more capable parts changer but not the best diagnostician) or just have the dealer do the work.

I have a shark fishing trip about 50 miles down the beach on Padre Island National Seashore coming up and without a reliable vehicle that I know will get me back and forth it will probably get canceled. That is major no bueno, so throwing a little more cash at it than I care to has become the best option.

I did have the transmission and transfer case fluid flushed just before this started, so an extra thanks to the person that mentioned that. I'm going to call and make sure they know that.

Much appreciated!

Killing threads since 2004.

[skydiver30960 0]

For future issues, PLEASE check out www.jeepforum.com.

I got a Jeep TJ a few months ago (my second since '97) and I've been doing more tinkering on this one than I ever did on the first. That website is AWESOME.

Elvisio "almost as cool as dz.com" Rodriguez

[FlyingJ 0]

I have frequented the Jeep forum in the past, but for some reason have been unable to connect to it the last few days. Not sure if there was a site issue or my computer at work was just throwing some attitude. Just visited the site now on my mac at home and got there fine.

The diagnosis via the dealer was "well, definitely no vacuum or intake leak," so we suggest you pay us $600 to do all of this other stuff and we'll see if any of that does it. So, I'll be working through some of those things on my own. More later when I'm not in a rush...

Killing threads since 2004.

[FlyingJ 0]

Having added a fuel system/injection cleaning and de-carb to the list I'm still stalling. A new throttle position sensor and rotor are waiting for a few minutes of free time to install. Hoping I can make that happen on Saturday!

Killing threads since 2004.

[FlyingJ 0]

Well, I'm cautiously optimistic after one week now without a stall. I replaced both the rotor and the throttle position sensor at the same time and the problem seems to be gone. Seems much more likely it was the TPS that was bad, but I didn't want to wait any longer to just knock out everything I needed to do. One nice thing after all that was done is that I'm seeing 1.5 to 2mpg better fuel consumption.

Killing threads since 2004.

[AggieDave 6]

Quote

Now the car starts and will run for about 5 seconds before stalling.

Have you tried lengthening the control lines a couple of inches? If you're not sure how or need help with the finger trap, your rigger should be able to help.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[warpedskydiver 0]

That was the problem, I have the 1995 Jeep Grand Cherokee and I too had to fix the same problem.

No more worries it will run fine now.

Just use some mobil 1 too and save any more troubles, plus you get 7500 miles on an oil change.

Just check your oil though, in that amount of time you could be low a little bit.

Did you do the extreme cleaning on the intake yet?

[squirrel 0]

Quote

Well, I'm cautiously optimistic after one week now without a stall. I replaced both the rotor and the throttle position sensor at the same time and the problem seems to be gone. Seems much more likely it was the TPS that was bad, but I didn't want to wait any longer to just knock out everything I needed to do. One nice thing after all that was done is that I'm seeing 1.5 to 2mpg better fuel consumption.

wish i would have seen this discussion before you took it to the dealer. just replace the TPS on my jeep, had the same issues, (different motor, i have an inline 6) $45 bucks.....all fixed, for now.

________________________________
Where is Darwin when you need him?

[FlyingJ 0]

Quote

Quote

Well, I'm cautiously optimistic after one week now without a stall. I replaced both the rotor and the throttle position sensor at the same time and the problem seems to be gone. Seems much more likely it was the TPS that was bad, but I didn't want to wait any longer to just knock out everything I needed to do. One nice thing after all that was done is that I'm seeing 1.5 to 2mpg better fuel consumption.

wish i would have seen this discussion before you took it to the dealer. just replace the TPS on my jeep, had the same issues, (different motor, i have an inline 6) $45 bucks.....all fixed, for now.

Well, everything done was well overdue, and only a few things happened at the dealer so I'm not out TOO much money. I had a feeling all along that the TPS was the culprit but had a couple issues that kept me from changing it early on. In hindsight I'm happy it worked the way it did as I would likely have foregone some of the other stuff if it had stopped stalling right away.

Jeep is paid off...really must keep it running!

Killing threads since 2004.

[FlyingJ 0]

Quote

That was the problem, I have the 1995 Jeep Grand Cherokee and I too had to fix the same problem.

No more worries it will run fine now.

Just use some mobil 1 too and save any more troubles, plus you get 7500 miles on an oil change.

Just check your oil though, in that amount of time you could be low a little bit.

Did you do the extreme cleaning on the intake yet?

No intake cleaning yet, but it's on the list. Going 7,500 miles between changes would be awesome, but I spend so much time driving on the beach (30 to 50 miles at a time up and down Padre Island for fishing) and on dirty ranch roads, etc. that I will pretty much always stick to a 3,000ish oil change.

Killing threads since 2004.

[squirrel 0]

Quote

.

Jeep is paid off...really must keep it running!

yep, not having a car payment is the only way to go. never had one, never will. our jeep is a 2000 cherokee sport, and has 265,000 miles and counting!

________________________________
Where is Darwin when you need him?