stalling/idling problems

I have a 1993 grand cherkoee. I have changed the plugs & wires, cap & rotor, air filter, given it an oil change, cleaned out the fuel injectors and throttle body. I also relpaced some cracked hose on the engine. All of these small repairs have greatly improved the performance of the Jeep, but the problem remains...when in drive only, and I am stopped, or creeping forward to a stop sign from a stop, the jeep will sometimes drop way low down to 0 while idling and will rev back up after shuddering severely briefly. Sometimes it straight up just stalls completely, but will start right back up with no trouble starting. The problem has been getting worse and happens more frequently. Anyone know what might be the problem? I would rather have an idea before I take it to get it looked at as I have already poured a lot of money into this car. Thanks, much appreciated!

Sounds like the IAC motor located on the back of the throttle body. Try cleaning the throttle boby and the Iac motor first with carb cleaner or starting fluid. If it does not fix your problem then you will have to replace the IAC around $60.

yea im thinking it might be the IAC motor since I cleaned out the throttle body quite thorougly, and that made for a much smoother idle when it doesnt decide to want to stall, but it still happens nonetheless. Thanks a lot. Any idea is this can be done yourself or if I should let a mechanic tackle it?

Maybe it would help if I described the problem like this--it will surge like its gonna die, and drop really low, the engine will shudder and sometimes it will stall completely, but usually it will rev back up and level off at around 1000 and hold steady, but if i pull up a little bit slowly and then come to another stop, it will do the same thing-surge a couple times and then level off. Does this help any? Still think its the IAC motor?

I have a 1995 Grand Cherokee with exactly the same problem. I just got home after stalling in a busy intersection for 20 min. The car has been in the garage and they were unable to find any problems. They cleaned the throttle body and the car worked fine for a couple of weeks. I put up with the stalling for a month or two not a big deal. But now I do not trust the car.

I woudl agree it sounds liek an IAC problem , b/c it only seems to do this when the throttle plates are closed, when the throttle is closed, the IAC opens to allow air to by-pass the throttle plates into the engine to keep it running.

try this to determine if the IAC is bad, start engine, place in gear (drive, Reverse), turn A/C on, and operate the power steering pump (turn wheel slightly right or left). the rpms should increase slightly or remain steady, if it drops or stumbles then the IAC is deffinately bad and need to be replaced.

the test above will only work on a bad IAC, the IAC could be going bad and not show these signs.

Maybe it would help if I described the problem like this--it will surge like its gonna die, and drop really low, the engine will shudder and sometimes it will stall completely, but usually it will rev back up and level off at around 1000 and hold steady, but if i pull up a little bit slowly and then come to another stop, it will do the same thing-surge a couple times and then level off. Does this help any? Still think its the IAC motor?

YOU MAY HAVE A PROBLEM WITH THE THROTTLE POSITION SENSOR
DALE jeepman600@aol.com

I think its the IAC, I found a good site for parts its www.rockauto.com. The iac valve, which is normally $60-80 is only $28 bones for anyone else having this problem. Thanks for the help y'all.

I tried the IAC test that was mentioned. The rpms remained steady at 1k. Does anyone know if hooking my jeep up to a computer will diag the IAC or Throttle Position Sensor? I am trying to weigh throwing money at the IAC before springing for the computer diag.

Yes the computer diag will let you know of IAC failure, the book actually mentions the only way to truely test the IAC is with a scanner.

i ordered a new IAC too to rule that one out, hopefully it will solve the prob

After placing my JGC on the diag machine we found it to be the crank sensor. There was also an error code in the computer for the crank sensor. Hopefully, my stalling days are done. If the IAC doesn't solve your problem you may also want to check the crank sensor.

Yup it was the crank sensor, it was kind of hard to get at but now that I know I could do it again. I also replaced the cap and distributor and finally no more stalling. experieicing. Thanks! I also replaced the cap and rotor and distributor and finally no more stalling. Now, however, when the jeep is cold, it starts right up but for the first minute of driving if it hasnt been driven all day, it is a bit jerky and hesitates a bit and is more hesitant around 20/30. Is this a fuel filter problem? Any suggestions

Prob. the computer relearnig, disco the battery awhile to reset. Did you install the IAC that you ordered?

I did and it didnt seem do change the idling at all back when it was stalling so i returned it. Maybe i should buy another one though? I think it might just be the fuel filter though.

honk- did you get the IAC from AUTOZONE (WELLS brand)? I had to replace my IAC and when I did it didn't do anything (then I remebered about a guy who replaced his twice before it helped his problems), well since AUTOZONE aftermarket supplier is not know for quality parts, I decided I would get a different brand/different store - then I remembered this one had a warranty so I took it back and got the new one put it on and it works fine now, it's been a lil over 2 weeks and has not had a starting problem yet.

NOTE: when you replaced the IAC did you disconnect the Negative Battery Cable - sounds dumb but I did forget to do this when I replaced the first one, it may or may not have caused the first NEW IAC to fail, I disconnect the Neg. Battery cable when I replaced it under warranty and it works fine. I doubt that the disconnecting the cable helped but it's a possibility.

Your right on that. I got it from a discount online store but it was the same crappy one that advanced auto sells. Ive found that dealer parts, while you pay more, are much more reliable and compatible than the generic ones. I dont have starting problems but only some slight hesitation now, maybe the computer has to "learn" the crankshaft sensor and distributor. By the way, the distributor was a remanufactured one from advanced auto, and ive heard sometimes they are not 100%. So i dont really know what to do now.

Wonder if you need to index the distributor.

Check out this link ... It turned me on to the crank problem and force me onto a diag system. I am wondering if you need to reindex after you installed both the crank sensor and distributor.. BTW .. I am stall free.. Knock on Wood.

I had the advantage of using a buddy's garage to figure out my problem. I ran the diag myself. It would have been worth the money to pay someone else to do the same diag.

Here's the link.. This guy is pretty good. I utilize him for some other issues.

http://www.asashop.org/autoinc/feb99/techtotech.htm

I have a 1995 Grand Cherokee Orvis with the same exact problem. I am stationed in Japan and have been to three Auto Repair Shops here including the Jeep Dealership, but they all have no clue. The only thing they replaced was the Spark Plug wires and other than that they cleaned throttle body. Every time the problem seems fixed until a week or two later when I find myself stalling when taking off from a stop sign or while slowing down during a turn in an intersection. Then there is that crazy random idiling when stopped. I just found this forum, so I am going to order a Crankshaft Position Sensor, IAC Valve, and pray it works this time.

Y8Tiger -- Would recommend factory parts

Good luck - I'm sure this will address the issue. I have received a number of responses to this post. This resolution has solved the problem for about 8 different jeeps.

this is a stupid question but, where is the crank sensor??

my 93GC hesitates and sputters, just dosn;t seem to do it in idle... I have ruled out the 02, map, tps sensor, that iat thing, dist cap, rotor, plugs, wires, computer, fuel pressure reg. I don;t knoiw what else to try

I had the Crankshaft Position Sensor and IAC Valve replaced at the local Jeep Dealer. Then I had a full service and inspection to include a Tune up. I was waiting to see what happened before I replied. For a week it drove perfect and we were so very happy.Then two days ago it stalled again. It stalled again once yesterday and twice today with the idiling problem returning. Every day it idles a little worse. I swear it is almost like every time they work on it they tighten something that comes loose a week later. My wife thinks we are cursed. Any other ideas?

this is a stupid question but, where is the crank sensor??

On the 4.0L engine the CPS is located on the Driverside bellhousing of the transmission, up toward the top of the bellhousing.

On the 5.2/5.9L engines, the CPS is located on the passengerside engine block right behind the right cylinderhead.

For replacing the Crankshaft Position Sensor, I've provided some guidance on the following posting:
http://www.automotiveforums.com/vbulletin/showthread.php?t=456307
Look for posting from JeepForever, on 9/17/2005, 2:17 PM.

This relates to a '94 Jeep Grand Cherokee 4.0L.

What if replacing the Crankshaft Position Sensor, doesn't do it? I am still trying to find another solution now that the CPS and IAC have failed to solve the problem. I stalled 6 times yesterday! While slow turning, taking off from stops signs and driving on straight aways at slow speeds around 20 kph. The more I read the more I see that the Grand Cherokee is not so reliable a vehicle. While living in Germany for 3 years, I drove a 10 year old 730I BMW that never gave me one problem. That was a reliable car and now I regret having not bought another.

don't give up hope, you will find the problem. I have a cherokee with the str8 6 motor, 175000 miles no major problems yet, don't get me wrong I have had to replace minor components, but the few negetives don;t detract from all of the positives...

I have the 5.2 V-8 engine and I've noticed that the stalling seems worse with the AC running. Does this make any sense? It also acts like it is gonna die when taking off from a stop sign so you never know if it is gonna stall or suddenly lurch forward. However, The most common stall comes when turning slowly.

these are deffinate signs of a bad IAC. Did you disconnect the battery before replacing the parts?

I had a problem last winter with my IAC, not like your, mine would start right up and die immediately (when the engine was cold). So I had to start it and hold the gas pedal in slightly for about a minute then it would be fine throughout the day.

I knew it was the Idle Air Control Valve, so I replaced it, and it didn't help, figured I prolly got a bad part from autozone, so I took it back (under warranty) and got a new one. started to replace it and remembered that last tie I didn't disconnect the battery and that might have been my problem (all repairs manual say to disconnect the battery before replacing any electrical component) so I disconnected the batt. and put the new part on and it has worked fine ever since then.

Now I don't know if I got a bad part from autozone or if it went bad because of my failure to disconnect the battery. But either way now I always remember to disconnect the battery when working on my jeep.

I figured that you had the 4.0 they are bullet proof motors, they run forever, I'm not sure on the 5.2l V8, I personally would prefer a 6 esp with gas prices...

Thanks for your help everybody! My wife went to the Jeep Dealership today. The Problem is now fixed and I have high hopes it will last this time. I also learned something very interesting:

I paid through the nose to have the Jeep dealership install the CPS because no other local places could do it. To save money I had a local shop replace the IAC Valve.

dksob81 to answer your question:

no, the local shop did not know to disconnect the battery. Today, the Jeep dealership found a computer fault saying that the computer needed too be re-initialized to accept the new IAC Valve. Jeep reset the computer using software, but they told us that when you disconnect the battery it physically resets the computer. Basically, like adding new hardware to your PC and then rebooting the PC by pulling the electrical plug. Jeep says the computer needs to be reset everytime when replacing any electrical components.

Knock on wood, Let's hope that this takes care of the stalling problem for good. I found so many websites talking about this problem with Jeep Grand Cherokees. I even noticed that http://www.quadratec.com is offering high performance Rock-It brand CPS and MAP Sensors that claim to be better than the stock ones. Once again thanks for your help everybody...I really appreciate it.

this is a stupid question but, where is the crank sensor??
crank sensor is hard to get at. if you have it on the ground, it's on the transmission bellhousing, left side of the engine, at the 10 or 11 o'clock position. my 93 gc has one bolt holding in a 3wire sensor and the harness crosses over to the connector on the right side of the engine, just over the starter. i think they had some different wire routing for different years, but this might get you onthe right track.

are the IAC valve and the IAC motor the same thing?

are the IAC valve and the IAC motor the same thing?

Yes, They are.

i have to unplug the battery in my wifes 93 gc and hope for a reset then? i hope this works.

i have to unplug the battery in my wifes 93 gc and hope for a reset then? i hope this works.

Yes, disconnect the battery before replacing any electrical components. *ie- Idle Air Control Valve and Crankshaft Position Sensor.

It has only been a few days but the computer reset has taken care of the stalling problem.

Shoot me now and put me out of my misery! The dreaded stalling/idling problems have once again returned.

Jeep dealer says they think the Idle Air Control Valve I purchased from www.rockauto.com has gone bad already. They are keeping it until they are absolutely sure this time around, but if this is true this will be the second overpriced substandard part purchased from www.rockauto.com in as many months. I am also not ruling out what dksob81 said about his experience with not disconnecting the battery first.

I tell you if this keeps up I will never be able to afford the K&N FIPK, AEM Throttle Body Spacer, Jet Performance Chip, Rock-it Hi-Flow Throttle Body and other upgrades I will need for driving on the Autobahn after I transfer.

My 1997 Jeep Grand Cherokee keeps stalling. It starts very rough, then when I take my foot off the gas, it just drops and dies.

My 1997 Jeep Grand Cherokee keeps stalling. It starts very rough, then when I take my foot off the gas, it just drops and dies.


Sounds like your IAC Valve is bad. Try holding the gas in for about a minute or 2 and then let go of it, does it stay runnin?

Now Jeep Dealership says the Computer and PCM needs to be replaced and that parts alone will cost $1,200.00. They claim that the computer gliches and causes a stall when running at 7% throttle and that PCM alone wil not fix it. Does anyone know if this sounds like an accurate price for those parts?

Now Jeep Dealership says the Computer and PCM needs to be replaced and that parts alone will cost $1,200.00. They claim that the computer gliches and causes a stall when running at 7% throttle and that PCM alone wil not fix it. Does anyone know if this sounds like an accurate price for those parts?

Computer and the PCM are one in the same. You can get one from partsamerica.com for around $200, here is an example of a 1993 Grand Cherokee 4.0L http://www.partsamerica.com/ProductList.aspx?parttype=248&searchfor=Engine+Computer&ptset=A

i have a 1998 jgc and it has the same problems and i have replace the iac the crankshaft sensor and the throttle position sensor and it still is haveing a prob stalling wheather i am driving or idleing it happens more at an idle but somtimes it will crank right up and idle then go just fine but 7 times out of 10 it will stall within a 20 min period. Do you have and suggestions?

i have a 1998 jgc and it has the same problems and i have replace the iac the crankshaft sensor and the throttle position sensor and it still is haveing a prob stalling wheather i am driving or idleing it happens more at an idle but somtimes it will crank right up and idle then go just fine but 7 times out of 10 it will stall within a 20 min period. Do you have and suggestions?


When it stalls, do you have to wait before it iwll start or will it fire right up after stalling?

Computer and the PCM are one in the same. You can get one from partsamerica.com for around $200, here is an example of a 1993 Grand Cherokee 4.0L http://www.partsamerica.com/ProductList.aspx?parttype=248&searchfor=Engine+Computer&ptset=A

Once again dksob81 you show that definitely know what you are talking about when it comes to JGCs. Thanks for the continued help. Now I need your support once again.

Japan Jeep Dealership Service Department says I need to replace the Power Control Module (PCM) Part# R6026794.

I emailed Jeep in the US about this part and I also noted a descrepancy between the Part# R6026794 that the dealer gave me and Part# 56026794 on the websites that offer PCMs for sell. I also noticed they have a variety of Names: PCM, ECM, Engine Control Computer, and ect.

It all gets a little confusing and I also read on a website that part#s beginning with "5" are OEM and part#s beginning with "R" are remanufactured. So I guess that means that the part that went bad was not the original and was once replaced before because of the "R"?

To top it off Jeep USA sent me this:

"Thank you for your follow-up email to DaimlerChrysler Motors.

Unfortunately, replacement parts can not be ordered over the web or via
telephone through DaimlerChrysler. They must be ordered through an
authorized DaimlerChrysler dealership.

I suggest you review the part number you included with your dealer, as
this part is for a 1995 Jeep Cherokee, 5.2 liter, automatic
transmission, for use with leaded fuel. Unless your vehicle has been
modified at some point, it was originally designed to use unleaded
fuel.
According to the parts catalog, the original equipment replacement PCM
part number is R6026790.

Thank you again for your email."

Talk about confusing...is this for real? Which one should I buy? All I know is Jeep Japan charges 124,800 Yen ( $1,248 ) for the PCM here and another 5400 Yen ( $54 ) to install it. They are out of their minds...HELP!!!

humm actually I am a lil confused from all that as well.

Do you have the ZJ or ZG (Foreign Model), I dunno maybe that has a differnce. After Searching all the parts sites, I am not sure what the "R" means exactly because all the partsites I visted shows your computer (OEM# 56026794)(aftermarket: Cardone # 796790) as a remanufactured computer but does not have the "R" in the part #. Now the R might be on the actual part# of the computer (noting it as a reman) in which you would need Cardone #796790 (http://www.partsamerica.com/ProductList.aspx?PartType=248&PTSet=A&SearchFor=Engine%20Computer) w/ or w/o Export Package, whatever the export package is.

Also while looking at it further, maybe the R has something to do with the Export Package, the Part# w/ Export Equipment Package shows OEM # 56026794 while the computer without Export Equipment Package does not show an OEM #, again I am not sure, just a thought. I guess knowing what the Export Equipment Package is would help.

I found a Mopar Remanufactured Parts Catalog online that stated that OEM parts begin with a "5" and Reman Parts begin with a "R".

Jeep Japan says this is the Power Control Module (PCM) Part# R6026794 in my vehicle.

PCM Part# R6026790 may or may not be accurate as this Canadian Spec. vehicle was special ordered for export to Japan.

I can't imagine Jeep USA being correct about the R6026794 being for leaded fuel? Who has used Leaded since the early 80's?

I still find this all confusing. I think I will have to just risk it and purchase the PCM w/ Export Equipment Package.

That also caught my attention, I think it may have been a typo, I don't think jeep ever made a ZJ/ZG that ran on leaded fuel.

Well Good Luck, hope it all works out.

That also caught my attention, I think it may have been a typo, I don't think jeep ever made a ZJ/ZG that ran on leaded fuel.

Well Good Luck, hope it all works out.

Typo located:

I looked under the hood and the PCM is labeled OE# 56026974 and dated 03/31/95 so I am guessing it is the original. The Jeep guy wrote "794" on the paperwork instead of "974".

somtimes it will crank right up after stalling somtimes i will hesitate and i will wiggle the wires and it will crank most of the times somtimes i just keep the starter going until it does crank up

After looking around the past few days on the Part websites I realized there are no OE# 56026974 PCMs for sale, but there are plenty of OE# 56026794 PCMs for sale. This leads me to believe that the white sticker label on top of the PCM must represent something else.

I guess it is better to purchase the OE# 56026794 PCM Jeep Japan told me to buy in the first place and if it doesn't work right I can blame them! ;)

dksob81 - did my homework to answer your question> My Canadian JGC is a ZJ, while the ZG designation is for Foreign countries outside of North America. This allows me to bring my model back to the US without conversion in accordance with the EPA requirements.

Since replacing the OE# 56026794 PCM, my JGC has been running just great. That computer was very hard to find actually in stock and end the end only RockAuto.com could provide one. Even though it wasn't the CPS or IAC that was causing the stalling/idling problems, I feel comforted knowing there are new ones installed anyway. Thanks once again everyone for the advice.

Since replacing the OE# 56026794 PCM, my JGC has been running just great. That computer was very hard to find actually in stock and end the end only RockAuto.com could provide one. Even though it wasn't the CPS or IAC that was causing the stalling/idling problems, I feel comforted knowing there are new ones installed anyway. Thanks once again everyone for the advice.
Y8,

What was your final cost for the computer parts and install? Thanks Mike

Hello,
I have a GTP 1996 3.4L and got 3 of the wires on the back injectors chewed by mice....yes mice......now after all is repaired, the car is irregular on idle. I mean that instead of beeing quiet at the regular 800-900RPM idle position, it start to shake and lightly accelerates/increases the RPM by itself to 1000RPM where the shaking stops but it goes down again and all starts again, otherwise it works like a charm. I didn't had this problem before having the car scanned for the main problem above which happened all the sudden one morning. The car barely started, the engine was sheking, no power on acceleration, engine light came on and after a day of scanning found the 3 injector wires chewed by damn mice....bloody kritters. Now that the wires are new, I have this IDLE shaking problem.......it is like the engine is late on the comands.....what I mean is the fact that if I get to a stop light....the RPM take a couple of extra seconds to go down to the usual 8-900RPM and there it starts to shake, as well as on NEUTRAL or PARK. Could someone please advice me on what to do? Could it be the IAC? Thank you in advance. By the way, no other errors on the scan!

Hello,
I have a GTP 1996 3.4L and got 3 of the wires on the back injectors chewed by mice....yes mice......now after all is repaired, the car is irregular on idle. I mean that instead of beeing quiet at the regular 800-900RPM idle position, it start to shake and lightly accelerates/increases the RPM by itself to 1000RPM where the shaking stops but it goes down again and all starts again, otherwise it works like a charm. I didn't had this problem before having the car scanned for the main problem above which happened all the sudden one morning. The car barely started, the engine was sheking, no power on acceleration, engine light came on and after a day of scanning found the 3 injector wires chewed by damn mice....bloody kritters. Now that the wires are new, I have this IDLE shaking problem.......it is like the engine is late on the comands.....what I mean is the fact that if I get to a stop light....the RPM take a couple of extra seconds to go down to the usual 8-900RPM and there it starts to shake, as well as on NEUTRAL or PARK. Could someone please advice me on what to do? Could it be the IAC? Thank you in advance. By the way, no other errors on the scan!

I don't think your proble is with the IAC, since your rough idle is around 800-900 rpms. Iw oudl say you have a missfire, maybe slight timing problem

Y8,

What was your final cost for the computer parts and install? Thanks Mike


Mike,

The computer cost me $258.00 and S&H cost another $20.00. Jeep Dealership Install cost me about $80.00, but I live in Japan and so prices are a lot higher here. Good thing is, I am getting $50.00 back on the core charge.

speed sensor

We are having this same problem with a 2006 Grand Cherokee, less than 6.5k miles. Dealership can't find the problem, surprise surprise. They seem incapable of doing anything unless the computer can find a problem. Pathetic.

Going to get rid of this piece of junk this weekend. I've been down this path before and I refuse to waste anymore time with this company. I wish I had time to tinker with it and find the problem but it is actually a dangerous defect and I don't want my wife driving that car around. Two days ago we got stuck in the middle of an intersection and brought two lanes of traffic to a screeching halt.

I will never buy a Chrysler again.

In April 06, the stalling/idling problem reared it's ugly head once again. The dealership claims the OE# 56026794 PCM I got from RockAuto.com was bad. I am now sending my original Computer to A1 Cardone to be rebuilt and returned. If this doesn't fix the problem I am going to offload this nightmare as soon as I get back to the States next year.

All, 2001 JGC Limited V8. At initial startup of the day, engine revs up to 2000+ rpm, then backs down, but on the way down, it bumps up and down again (lower rpm this time), until it eventually finds rest at a normal idle rpm. once it's warm, it won't have the problem until it's off and cooled down for quite a while, then on startup it'll do it again. Any takers?