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97 GC stalling and LOW idle for SIX months now.

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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Thu Nov 15, 2007 12:51 am    Post subject: 97 GC stalling and LOW idle for SIX months now. Reply with quote

97 GC Laredo 4.0 186K miles. Runs strong when it runs correctly.

History: This all happened just before the stalling and low idle started...so bear with me, please:

Driver's side master window controls started acting up a few weeks after the air conditioning water drain backed up. Drain fixed. Only passenger side window operates from passenger door.
Locks dont work from driver's window either. No broken wires in door boot. Tried a junk yard master control unit for driver's side....no change. Replaced radiator, too. Left turn signal freaking out, too...just cant remember to buy the relay. THEN the stalling and low idle STARTED.

New battery and cleaned clamps to a shine.
New TPS ( although suspect)...Wells brand.
New IAC , cleaned throttle body..no change...so I reinstalled the original MOPAR.
New CPS ( MOPAR)
New Cam sensor ( autozone), distrib. cap, rotor, plugs.
New Coolant temp sensor.
New primary coil.
Cat convertor is one or two years old. ( meineke)
Backed out two torx screws on PCM ( a known issue...they are too long)

It seems to occur mainly at idle or with rapid deceleration.
Sometimes, I can floor it...and it lopes as if the timing is off badly....and sometimes it comes back and runs right. Other times it just dies. It also backfires LOUDLY sometimes when it does this. I noticed something interesting last week. I slowly drove over some rough ( side to side) terrain and it IMMEDIATELY went into "stupid" mode...sputtering, etc.
This isnt the first time it's acted up right after I rocked it sideways ( going out of a driveway, etc).
Idle speed is now fine upon cold start. ( 99% of the time) Once it warms up...idle drops to 300-500 RPMs. I keep my foot on the gas at redlights. Today, it acted stupid ( low on gas, heading into a gas station at the time)....and it sputtered....and backfired and died after I threw it in neutral and floored it. Bought gas...it sputtered and died a few times at the gas station, then it finally ran OK....although it idled low again. It threw a code 14 and a 43 on the odometer. Had it scanned..and it was MAP sensor voltage too HIGH ( not low)....and the primary coil thing again. I have wiggled wires til im blue in the face. This engine runs so well at high RPM ( over 1000).....it's hard to imagine it doing this crap.
Replace MAP sensor today. Disconnected battery, turned on key and cleared the codes. Still idles low.
Oh...fuel tested OK at rail last week...40 something lbs at idle.

The " rocking" thing almost tells me it's either a loose wire, or fuel pump related. ( or some other fluid). Looked for obvious vacuum leaks too. None found. This is getting expensive. I dont think it needed a map sensor. Oh...by the way...voltage to map sensor plug was 5.1 volts with key on, and sensor disconnected. I think it's the low idle that causes the problem. It begins to stall, misfires...and the PCM looks for the first code that it can, as the engine is trying to stay running.


HELP ! What did I miss, or do wrong ? This is my third Jeep and I love it....but it's close to being replaced by something else....that is NOT a Jeep...and I dont want to do that.


Last edited by Oldfrog on Wed Feb 20, 2008 7:34 pm; edited 1 time in total
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EYESIC
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Joined: 21 Sep 2007
Location: ARIZONA

PostPosted: Thu Nov 15, 2007 11:27 am    Post subject: thats jeep for ya! Reply with quote

haha it seems that every problem youve had ive gone through.. you pretty much covered everything.., hmm a similar thing was happening to me i cleaned out the throttle body with a throttle body cleaner and i checked all the hoses coming from the intake manifold and yep one of the hoses was sucked.... so i replaced it. after that my jeep began to function like it used to.

oh yea i also took the injectors off, the rear 3 had like gunk on them. I cleaned mine with gasoline, when i was finished a bought a fuel injector cleaner and put that in my gas tank.
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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Fri Nov 16, 2007 12:46 pm    Post subject: still stalling Reply with quote

No vacuum leaks that I can see. Today, it still idles low and I was sitting at a redlight, slightly uphill. It stuttered...as if someone hit me in the rear. I managed to keep it running...and took off....keeping the rpms high. It seems to do Ok during the warmup cycle, but it's a bit rough.

It feels like I lose all ignition power at once for a second....or there is water in the gas and as it hits the injectors it tries to die. I have put HEET in the tank a few times in the past and will do so today. My plug wires are a year old, and cheap ones, so I'll replace them too tonight.

Does anyone have ANY idea what this could be?
( see my first post as to what I've done thus far)
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ken692
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Joined: 15 Feb 2007

PostPosted: Fri Dec 07, 2007 7:43 am    Post subject: Reply with quote

recheck the TPS it cost me $300 for the greese monkey to change it
I bet you can get one for less than $75
http://cgi.ebay.com/ebaymotors/THROTTLE-POSITION-SENSOR-TPS-TH143-JEEP-GRAND-CHEROKEE_W0QQcmdZViewItemQQcategoryZ33557QQihZ019QQitemZ290137155227QQrdZ1QQsspagenameZWD1V
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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Fri Dec 07, 2007 9:15 pm    Post subject: did that Reply with quote

Replaced TPS again, just to be safe.
Since cold weather has arrived, it seems a bit better...but it still just shuts off....just as of I turned the ignition off. If the RPMs are below 1500 at the time, it usually dies....or begins to diesel if I throw it in neutral while stopped and give it gas. Sometimes it recovers, sometimes not. If it dies, I can restart it by giving it a lot of gas , with a long cranking time.

The stalling ( it feels like a BUMP when driving down the road when it happens)......is MUCH worse when the weather is warm and usually occurs when the engine temp is at operating temp. Rarely stalls at below operating temp, but it does happen.

Tonight, I made a short trip...pulled up to a light, kept my foot on the brake and eased the RPMS to 1000, while sitting still. It cut off...the RPMS dropped, I slammed it in neutral, gave it gas ( a lot)....and it backfired through the muffler and began running again. It was warm outside and my gas tank was low at the time. It tried to cut off a few times while I was running down the road, but I guess it restarted itself due to my speed. 99% of the time the stalling problems occur at low RPMs...and especially at idle...so I rarely allow it to idle anymore. I make short trips each day....less than 5 miles each and make sure I run the tach up to at least 3500 RPM once a day to rotate the valves.

HELP ! Does ANYONE have any other ideas?
Cat Convertor? O2 sensor?
The last code I got was a 43....misfire. But it usually doesnt throw a code.
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Orangeamc13
Got Rev Limiter?
Got Rev Limiter?


Joined: 20 Feb 2006
Location: East Springfield, Massachusetts - U.S.A.

PostPosted: Sat Dec 08, 2007 8:28 am    Post subject: Reply with quote

Fuel filter?
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OnAll4s
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Joined: 25 Apr 2007
Location: Seattle (actually Renton), WA

PostPosted: Mon Dec 10, 2007 7:30 am    Post subject: Reply with quote

You have a lot of new stuff in there, but have you cleaned your throttle body lately?
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ken692
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PostPosted: Mon Dec 10, 2007 10:46 am    Post subject: Reply with quote

sounds like you slipped a tooth
timing chain
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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Thu Dec 13, 2007 11:17 pm    Post subject: Reply with quote

Throttle body has been cleaned. ( not removed and cleaned, but sprayed and cleaned as well as it could be without removing it)

Not a timing chain slippage. It runs too well most of the time.

Noticed something this week.
Filled the gas tank all the way up. ( rare for me)
No stalling. no loss of ignition. Still idles at about 500 though.

Tank got down to 1/2 a tank.
It started acting up again.

I've put several bottles of HEET in the tank last summer ( alcohol) and one bottle of gumout injector cleaner.

I also noticed that when I was at idle, on a hill, facing up hill at a redlight, it seemed to stall.....then it would backfire thru the exhaust after I threw it in neutral and gave it gas. It would then resume running.

The hill and the full tank seem to have some effect on it.

So does outside temp...at times....although I ran all week with a nearly full tank and didnt have any problems until it dropped below 1/2.

Now, tonight, it acted crazy with less than 1/2 tank of gas in it. Started running rough, tried to stall at idle, backfired thru exhaust when it began running again. Is there something in the tank along with the fuel pump and filter that heat or lubrication ( from the gas in tank) would affect?
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Orangeamc13
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Joined: 20 Feb 2006
Location: East Springfield, Massachusetts - U.S.A.

PostPosted: Fri Dec 14, 2007 10:31 am    Post subject: Reply with quote

There are a couple hoses on the sending unit that can come off. That would cause your problem definitely. Drop the tank and pull the pump to inspect it.
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Orangeamc13
Got Rev Limiter?
Got Rev Limiter?


Joined: 20 Feb 2006
Location: East Springfield, Massachusetts - U.S.A.

PostPosted: Fri Dec 14, 2007 10:55 am    Post subject: Reply with quote

Here is a similar situation.

http://www.jeephorizons.com/phpbb/viewtopic.php?t=12735&postdays=0&postorder=asc&start=0
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Oldfrog
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PostPosted: Wed Feb 20, 2008 10:22 am    Post subject: Reply with quote

Update : Changed fuel pump/filters and cleaned the tank.

It ran well for 20 miles, then the next morning after it heated up a bit it started the stalling, stumbling again. After four bad start attempts, the computer reset and it started. Went 1/2 mile and missed a couple of times. I pulled over, killed it. Let it sit for a minute and restarted it.

Well, at least we know it's electrical and not fuel. The only reason it ran fine for 20 miles was because I had disconnected the battery durung the fuel pump swap. Once it relearned....it started it's crap again.

Does anyone have any idea what this problem is? It got BAD a few days ago...and would start-die-start-die on me . That's why I replaced the fuel pump.

Oh yeah, I'm getting some oil in my air cleaner. I guess that's a CCV hose that's plugged or some bad blow by. Would that do it?

HELP ! Someone has to have an idea. I'm running out of money trying to fix this thing.


Last edited by Oldfrog on Wed Feb 20, 2008 11:00 am; edited 1 time in total
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Oldfrog
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PostPosted: Wed Feb 20, 2008 10:26 am    Post subject: Reply with quote

One other thing I've noticed. I dont think the check engine light ever lights at all anymore.......even when I start it.
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RussellRowell
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Joined: 09 Feb 2006
Location: Jacksonville Florida

PostPosted: Wed Feb 20, 2008 6:36 pm    Post subject: Reply with quote

Hey There. Was reading your problem and wanted to ask a few questions. About 4-5 years ago, my fuel pump went bad. Had it replaced at the stealership. They asked me if I wanted the wiring harness replaced as well. Said I should since they were in there. I said no at the time because of cost. Anyhow, time went on and one day my gas gauge was just under half a tank and my jeep started doing what you describe about yours. Ever since then, I always have to fill up at half a tank or else it does what yours does. So at what level is your gas gauge at before it starts it's problem and your DTE (in your overhead console). And when you fill up, what does your DTE read? If it's doing what mine does, I think there is a problem between the computer and fuel sending unit (elec harness). Did you change out the electrical harness along with your fuel pump?

One other thing to try is while the engine is idleing ruff, take a small propane torch from home depot and turn the gas on but do not light it. Point it at all the vaccum lines you can find. Run it along the hoses slowly. If your engine suddenly revs up, you know you have a vaccum leak. Some vaccum lines run under your wiring looms on top side of the valve covers. Hopefully, you have a vaccum schematic on your radiator. Mine does.
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Oldfrog
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PostPosted: Wed Feb 20, 2008 7:23 pm    Post subject: Reply with quote

I did not replace the harness at the gas tank. I merely replaced the fuel pump, fliters and cleaned out the tank. I didnt buy the assembly, only the Airtex pump and filters. My fuel sending unit was recalled in 1998, I believe. the dealership replaced it at that time. ( not that it means anything now).

A while back, I thought the stalling problem occured only when the tank was blow 3/4 of a tank. It DID seem to do it less when the tank was full. In fact, I was almost lead to believe that as FACT.....until it started dying it at 3/4 of a tank and above. Later....it would NOT die at 1/2 tank. I've tried to establish a correlation between outside temp and the stalling. It does seem to do it less frequently when it's cold outside.

I have never noticed the DTE on the overhead console when it was stalling.

All I'm certain of, is that it loses power to the coil when it wants to and it either dies, bucks once or twice or it goes into limp ( out of time) mode.....stuttering at a very low RPM. ( just as a two stroke motorcycle engine will do, when it's loaded up....and/or has a fouled plug.)

It does seem to be heat related....but it's been so unpredictable I cant say for sure.

The "full tank" scenario, if it actually exists, MAY not have anything to do with fuel. It may have something to do with weight distribution. Maybe....there is some wiring that gets pulled away from a grounding point when the tank is full. Maybe somewhere like the wires near the coil that run along the passenger side motor mount area. I've jiggled and check them, but no luck, since that are locked down so tightly in the harness holder near the oil filter.
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