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97 GC stalling and LOW idle for SIX months now.

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kaos
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Joined: 10 Jan 2006
Location: Iceland

PostPosted: Thu Feb 21, 2008 12:05 am    Post subject: Reply with quote

One thing that strikes me is that your problem seems to be at it's worst just when the engine should be at optimum operating conditions, i.e. warmed up. Almost seems like the problem is only there when it is running in "closed loop", i.e. adjusting fuel mixture according to the feedback from the oxygen sensor. Have you tried replacing that, and/or checking it's harness and connections? Just a thought.

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Best regards,
Kári
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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Sat Feb 23, 2008 1:29 pm    Post subject: Reply with quote

I have thought about the closed loop thing. But every once in a while it starts from a cold start, and then dies, 5 seconds later. The O2 sensor is not in the loop at that time. Last nite it ran fine for a while. Outside temps were in the low 40's. I parked it for about 3 hours on a very slight uphill slope during that time. I came back to start it...it started and died. It took more than 3 tries to get it to start. ( I think 4 non starts will set the ECU at default settings).

So I think the "heat soak" thing is a clue...and I'll tell you why:
Once it stops and is parked for a while, the engine compartment heat rises a bit for until it finally begins to cool again. During that time, something ( electrical )physically shifts, ever so slightly and stays in it's new physical postion. Maybe it's a wire, a connector, a ground....whatever.

I try to start it, and the ECU "sees" this electrical malfunction, trips the ASD and it's all over.

After a few tries at starting, the bad connection gets just enough of a connection to allow it to start again.

Or, the ECU, by going to default mode, readjusts something and allows it to start. Who knows? But this heat soak theory sure seems like it's a player in the whole scenario.
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kaos
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Joined: 10 Jan 2006
Location: Iceland

PostPosted: Sat Feb 23, 2008 3:42 pm    Post subject: Reply with quote

Well, that knocks that theory on the head.

I did wonder if it could be a heat problem, although more in terms of faulty components, only you seem to have replaced pretty much all critical components, with the exception of the ECU (frightening thought).

It could, as you say, also be thermal expansion in a connection or even a broken wire. The only thing that I can think of regarding that is the "fine toothed comb" approach. Pull every visible connector apart, check for corrosion, give it a squirt of contact spray anyway and reassemble. *And* get a wiring diagram to discover any connectors not immediately visible. Also, another approach might be, with the motor running, to poke around and jiggle every connection and wire harness in sight. If the engine falters, it could be a sign of a bad connection in the vicinity.

And finally, just because it is a particular "favourite" of mine, having suffered from it in the past: You *have* checked your ground straps, haven't you? Engine to chassis, battery to engine, battery to chassis?

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Kári
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camparks
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Joined: 23 Feb 2008

PostPosted: Sat Feb 23, 2008 5:07 pm    Post subject: Reply with quote

I may have overlooked this in your replies - But have you actually tried to pull engine codes? You can go to Autozone and have them pull them for free. Jeep also builds in codes which can be displayed on the odometer display after a sequence of turning the ignition key. Consult your owners manual and search online for the codes definitions. Codes will be shown if there is a malfunction in the control loop.
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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Tue Feb 26, 2008 1:07 pm    Post subject: Reply with quote

Ground straps. Well, I have checked, cleaned and tightened what I could find, yes. What I have NOT located is the engine to body strap that's supposedly on the back of the block or head. All I have found are :

1. battery to fender connection.
2. TWO harness locations on the sides of the engine block. One each side.

Where in the world is the ENGINE block to frame/body strap ? I cant see or feel a thing behind the head, at the firewall.

I pulled the ECU plugs Saturday, sprayed them with contact cleaner and backed out the two infamous torx screws a bit more. I havent driven it more than a mile ever since. ( out of town on Sunday).

97 4.0 GC......anyone KNOW exactly where the engine to body ground strap is located ?

I'm also told that there is a central ground for the pwr windows/door locks somewhere under the dash on the firewall. The air cond. drain was stopped up for a while so I wanted to take a look at that ground too...if anyone can tell me where it is, exactly.

And yes, I've pulled codes multiple times, the most common is the one that says the coil isnt getting voltage due to circuit malfunction. ( new coil and no evidence of bad wiring that feeds it).
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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Fri Feb 29, 2008 10:09 pm    Post subject: update Reply with quote

Here's an update, maybe with some good news for a change. Keeping my fingers crossed !

I have driven it a little over 100 miles in town now, since the fuel pump replacement, cleaning out the gas tank, and more recently, pulling the ECU connectors and spraying them with contact cleaner, backing out the OUTBOARD torx screw on the front of the ECU cover a bit more, swapping out the coil wire, adding a quart of oil and filling the tank with fresh gas.

It has barely tried to act up ( bucked and nearly died)....only three times...and it NEVER died !

So, here's ONE theory. It was the fuel pump and water in the tank.
After I had drained the tank and cleaned it out, I had to pour about 2 gallons of the old gas back into the tank in order to get to a station to fill up. Well, I went home from my girlfriends place that night( after replacing fuel pump) and didnt fill up on the way...since I dont live far and it was late. As I poured the gas back into the DRY gas tank, I tried to make sure I only poured the gas off the "top" of my gas cans, leaving any water in the bottom of the can, thus NOT pouring it back into my Jeep. I poured a little from each of the two, five gallon cans, so as to not disturb any water that settled.

I MAY have gotten a little water in my Jeep....but not much if any. And THAT could be the NEW reason it has tried to stall ( bucked and sputtered three times in 100 miles)...but did NOT stall. That was theory number one.

Theory number two is :

The ECU connectors were the problem, OR the outboard torx screw that I backed out even MORE could have been the problem ....and the bad fuel pump was only ONE of the original problems. ( along with water in the tank)

It could have, of course, been the coil wire that I swapped out. The plug wires were about 18 months old and I had bought a new set, that was sitting in the box...so I swapped out the coil wire only.

I wont keep you hanging, though. I will drive it and put some SERIOUS miles on it tomorrow and see if the bucking or the stalling comes back.......and THEN I WILL post to help anyone else that has had this trouble.

I'm guessing that I had multiple problems that overlapped and masked the main one. Time and more miles will tell. I just pray that it's fixed !

I'll be back soon.
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viper24242
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Joined: 08 Jul 2005
Location: Harrisonburg, VA

PostPosted: Sat Mar 01, 2008 10:38 pm    Post subject: Reply with quote

OK, I'm not gonna lie, I haven't been on in a while and I apologize that I didn't want to read the two pages of posting but here is a thought if it already hasn't been considered.

My 5.2L zj stalled and died and died at low rpm because the Inlet Air Control Valve (I believe is the correct term) was bad. After replacing the cat it was fine but then in cold weather it would act up, or die at low rpm again. After replacing the IAC, no problems for at least a year.

Like I said, sorry about not reading through the whole post and I'm soory if this point has already been raised, but if not, hope this might be the solution.
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Orangeamc13
Got Rev Limiter?
Got Rev Limiter?


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

PostPosted: Sun Mar 02, 2008 8:40 am    Post subject: Reply with quote

12/8/07
Orangeamc13 wrote:
Fuel filter?


12/14/07
Orangeamc13 wrote:
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.


12/14/07
Orangeamc13 wrote:
Here is a similar situation.

http://www.jeephorizons.com/phpbb/viewtopic.php?t=12735&postdays=0&postorder=asc&start=0


It seems like was really warm with my diagnosis! Mr. Green

Glad to hear that it's working for you. So far! Wink

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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Tue Mar 04, 2008 1:38 pm    Post subject: Reply with quote

update:

It tried to stall a few times during the 240 miles I have put on it since the last work was performed.

Last nite, out of nowhere, it acted stupid again. Arrgh ! It was drizzling rain and cold. The rain has never been a problem before. I pulled over, let it idle ( after restarting it once again) and wiggled the plugs on the ECU cover.

It died. I thought it was a fluke, so I started it once again. It was running a bit rough, so again I wiggled the plugs. It would clear up and then die. Restarted it again and let it idle. Watched it without touching anything for a minute. Then I wiggled them again, particularly the inboard plug....in all different directions. It would clear up but I couldnt hold it there....then it would act up again. So I got it running again and drove to my girlfriend's condo, where we were heading at the time anyway.

Oh, BTW this is the second time I've put more gas in the tank since the fuel pump. I filled up again at 1/2 a tank.

After about 2 miles.....it really started acting up....stalling, and bucking....and while it was trying to restart it backfired TWICE, loudly....but it restarted. Pulled into her carport...let it idle and it was fine. Came back out, started it and wiggled the inboard ECU plug.

NO CHANGE. It ran pefectly. I left her place at 4 AM and it did OK all the way home...( about a 10 minute drive).

I noticed that there is a little plastic piece that came off the ECU plugs when I pulled them earlier in the week. No way to put them back in. They lie on top of the plug somehow.

Today, I'll pull them again, spray with contact cleaner and see what happens.

Should I put dielectric grease on them or not? There was no sign of any grease ever being on them when I pulled them the last time.

I'm getting close....but still no cigar. I could be buying gas with water in it and not know it. That would really tick me off.
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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Tue Mar 04, 2008 4:02 pm    Post subject: Reply with quote

Update: Ok, I go outside, start the Jeep, and wiggle the heck out of the ECU connectors again today....just as I did last nite. Ran perfectly. I couldnt get it to die or sputter.

This is driving me nuts.
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johnnykomac
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Joined: 28 Feb 2008
Location: Oahu, Hawaii

PostPosted: Thu May 15, 2008 9:25 pm    Post subject: Reply with quote

I found your post on a search.

I have a very similiar post in gen tech right now under 'backfires'. I have an xj but the 'exact' same problem and it started after a 4x4 session, very similiar to the side to side action you mentioned.

THIS THING IS KILLING ME! and you too it seems. We have to figure this out!

ive replace-

egr valve
alternator
battery
plugs
wires
rotor
cap
fuel filter
batt cables


have you tried replacing the ignition module under the coil.

John
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Oldfrog
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Joined: 15 Nov 2007

PostPosted: Mon May 19, 2008 1:36 pm    Post subject: so far... Reply with quote

It's been narrowed down to the three plugs on the computer. It would die, I'd get out, wiggle them, and pull the face plate out a bit at times and it would be fine.

Last week it ran fine...only died maybe twice and restarted on the first try.

Either I have the wires or connectors in the "right" place now or something has changed since I began running my air conditioner.

As I recall, the air unit drain was stopped up for a long time last summer, soaking my passenger side carpet. I tried several times to unstop it without much luck....so I drilled a small hole in the floor board and let her rip.

I seem to remember a grounding point being mentioned for all the electric windows being somewhere under the dash near the air unit. Maybe that has something to do with it, since I cant find the window problem either.

For now....I think it's the ECU connectors. Ive cleaned them once and backed out the two torx screws as was suggested....but I'll spray them again soon with contact cleaner if it dies.
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johnnykomac
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Joined: 28 Feb 2008
Location: Oahu, Hawaii

PostPosted: Thu May 22, 2008 8:27 am    Post subject: Reply with quote

Mine is at the mechanic. Crossing my fingers.
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drv4show
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Joined: 31 May 2008

PostPosted: Sat May 31, 2008 10:16 am    Post subject: Reply with quote

Read your saga. Thought I would add one insight. my 97 GC was running rough a few months back (not as ad as you are describing). So I also did a complete tune up plugs, wires, cap , etc. It had 60k on the existing parts. When this was done it ran jut as rough as when I started. Couldn't find anyting wrong either. I had heard before that some Chrystler products were very votage sensitive. I did not have any indications that my battery was weak (cranked over just fine). I checked the voltage anyway, and it was 10.75 volts. Changed the battery, and it has run like a top ever since.
Sorry for he long winded responce. Hope it helps
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