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Unread 12-12-2008, 03:30 PM   #1
hotmomma
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Jeep Cherokee has rough/low idle and is stalling

Hi you guys. I am trying to figure out why my 87 in-line 6 Cherokee is stalling on me. About 9 months ago, it had a REALLY high idle upon starting, and I had the TPS replaced and ground wire work done. This fixed that problem. Now, suddenly, it is starting at a really LOW idle and has to warm up before I can get it into drive without stalling. Also, when I stop in traffic, it stalls on me unless I put it in neutral and accelerate a bit to keep it going.

I just wondered if my previous problem could have something to do with this one. I've replaced the fuel filter, plugs, and plug wires and have run Seafoam through the gas tank, thinking maybe there was water in the fuel.
What else could it be? Thanks for any suggestions.

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Unread 12-12-2008, 04:27 PM   #2
tjwalker
It's the crank sensor!
 
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I'd suggest first cleaning your idle air control and throttle body, then test and adjust your throttle position sensor (your vintage TPS is adjustable).
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Unread 12-12-2008, 04:31 PM   #3
hotmomma
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Another thing I just remembered is that it seems I "run" out of gas at 1/4 a tank, instead of getting to empty. It started doing this about a year ago. So, maybe my problems are in the gas tank? Maybe I need to do a fuel pressure test. According to a thread on here, my fuel pressure needs to hold at least 31 psi. I'll try that. Would that show me if there is something wrong in my gas tank? When I replaced the filter, the gas was rusty colored, but there wasn't really any debris that I saw.
Would excess water in the fuel be doing this too? Because I had bought a locking gas cap that never really fit perfectly and am wondering if that put alot of water in my tank.
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Unread 12-12-2008, 04:32 PM   #4
hotmomma
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One more thought, though. Wouldn't fuel tank problems make her stall while accelerating too? She only stalls when idling or right after start up if I don't rev her.
Sorry, just talking to myself here...
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Unread 12-12-2008, 04:35 PM   #5
tjwalker
It's the crank sensor!
 
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Fuel pressure testing is never a bad idea. It's easy to perform on the schrader valve on the fuel rail. Excess water in the fuel can create a bunch of driveability symptoms. Have you seen this symptom for more than one fillup of gas? If so, that's probably not it. A lot of gasoline formulations already have alcohol in them (up to 10%) which helps absorb water, not sure what you guys are running in Tenn.
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Unread 12-12-2008, 04:37 PM   #6
hotmomma
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Thanks tjwalker for responding. I've got some seafoam, can I use that to clean the IAC? Seems like this Jeep has always had throttle body and tps problems. I replaced the TPS back in April. Maybe they didn't adjust it. But would it take 8 months to start acting funny?
Another thing I just thought of is about a month ago, she wouldn't start in the parking lot. Just turned over, but wouldn't start. I had her towed. Later that night she started. One other time she wouldn't start, so I popped the hood and "touched" a bunch of stuff (I know, sounds creepy) and then she started. It was only after those two times is when she started idling so low and rough and stalling on me.
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Unread 12-12-2008, 04:42 PM   #7
hotmomma
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I've filled up quite a few times, so I guess that probably isn't it. It's weird that she is now "empty" while still showing 1/4 a tank. But I am totally out of fuel at 1/4 tank.

What's that thing called near the TPS that you can move to accerlerate the engine just as if your foot is on the peddle? Is that the idle air control? If so, can that be adjusted? My mechanic said he didn't think it could, but I'm almost positive I watched him adjust it when she was running a really high idle. I also just had the idle air control motor replaced (well, 8 months ago).
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Unread 12-13-2008, 01:20 PM   #8
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Well, I tested the EGR valve and it seems to work fine. When I took off the vacumn hose, the Jeep stumbled/stalled.
Now I am going to clean the IAC. Would a dirty IAC cause intermittent stalling?
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Unread 12-13-2008, 01:37 PM   #9
88XJSport
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Quote:
Originally Posted by hotmomma View Post
Would a dirty IAC cause intermittent stalling?
Yes. The pintle gets gummed up with carbon, and the place it resides in the throttlebody also gets full of carbon. Clean the IAC pintle with throttle body cleaner, and do not twist or pull on the pintle. Also clean the hole where the IAC resides in the TB also.

Dont be suprised if the IAC still causes problems. The fact that you changed the TPS, and still get high idle, and now its low idle and stalling, may mean that the IAC pintle is not retracting or extending like it should anymore, and is causing high idle/stalling issues. You may just have to replace the IAC.

I know this because I experienced this for myself on my 88.
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Unread 12-13-2008, 01:56 PM   #10
hotmomma
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Well, the IAC and the TB where it goes in are pretty clean. I don't see ANY carbon buildup on the pintle.
Mebee my TPS is bad again?
Would a ditry carb cause problems such as this? I ran seafoam through my fuel tank. Would that also clean my carburator?
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Unread 12-13-2008, 01:58 PM   #11
hotmomma
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I have another can of seafoam. I think I will add it to the air intake and vacumn system; see if that helps.
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Unread 12-13-2008, 02:02 PM   #12
88XJSport
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Remember there is no carb on a 4.0 Cherokee. Everything is fuel injected. How does your throttle body look in general when you remove the air hose? F it checks out, then Id adjust your TPS to spec again...
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Unread 12-13-2008, 02:25 PM   #13
hotmomma
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Well, I did end up getting some crud out of the TB where the IAC goes in. Started it once, and it was the rough start, started it again and it was a good, normal start. I'm cunfuzzled why one minute it is abnormal, and the next it is normal. I think I may just replace the IAC.
This may be a stupid question, but would a ground wire or something like that make the IAC go bad after time? It seems like I had it replaced before and they also bypassed some wires or something. I need to get out my paperwork to see what was done.
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Unread 12-13-2008, 02:29 PM   #14
hotmomma
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When I removed the air hose from the TB there was some crud around the perimeter of the TB and on the gasket of the air hose. Cleaned it all off, and those little door thingies that open up (sorry for my lack of correct terms here). The problem is, I can't tell if these things are working, because one start will be bad/rough and the next willl be good.
You're right. I knew there was no carb. My brain is becoming fried.
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Unread 12-13-2008, 02:31 PM   #15
hotmomma
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Is there a way to test the TPS with a voltmeter or some such?
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