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  #1  
Old 07-15-2016, 09:13 PM
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Rough Idle & Stumbling

I have a problem with rough idle and stumbling taking off. If I keep the rpms over 2,000 it runs fine. A few days ago the 0302 code poped up so I changed all the plugs, gapped them at .40. Still had a rough idle so I tried a new TPS, the old one fell apart when I tried to remove the wire connector. Well the new one didn't help the problem. I tried some new gas with a cleaner and that seemed to help a little but the problem is still there. I looked at the vacuum lines and they all look good. The plug gap of .040 seems small but that is what's on the sticker under the hood. Anyone with any ideas on what I'm missing or should check. There are no codes.

Thanks...

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  #2  
Old 07-15-2016, 09:49 PM
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Re: Rough Idle & Stumbling

What are you driving? If you add the vehicle info to your profile it will appear on every post. Many of the knowledgeable guys that could answer your question have quit asking and just go on to other posts. Just a heads up.
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  #3  
Old 07-15-2016, 09:56 PM
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Re: Rough Idle & Stumbling

Thanks, I will add that to my profile. I wasn't thinking, it's a 2004 Grand Cherokee Special Edition 4.0
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Old 07-15-2016, 10:06 PM
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Re: Rough Idle & Stumbling

No worries. Hopefully a mechanic will come strolling by shortly.

How many miles? Original plug wires? Original fuel filter?
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Old 07-15-2016, 10:24 PM
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Re: Rough Idle & Stumbling

322,000 kilometers, no plug wires and new Champion plugs. I bought this Jeep 7 months ago so I don't know how old the fuel filter is. I don't normally drive it in the summer but I blew the transmission in my 86 Grand Prix summer car and i have not had a chance to see what that problem is but it's a 5 speed stick so it's easy to fix.
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Old 07-15-2016, 10:55 PM
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Re: Rough Idle & Stumbling

I would not expect the fuel filter/pressure regulator, since its running ok above 2000 rpm.
I would at least check/clean the idle air control stepper motor plunjer and the air canal in the throttle body and check again.
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Old 07-16-2016, 02:37 AM
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Re: Rough Idle & Stumbling

Thank you, I'll try that in the morning let you know the results...
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Old 07-16-2016, 03:29 PM
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Re: Rough Idle & Stumbling

I removed the throttle body, removed and cleaned the idle air control plunger which wasn't that dirty and cleaned the air canal with seafoam. I also ran some seafoam into the intake with the engine running. The engine ran smooth for a minute or so then started to run rough. It's noticeably better than before but it is still rough but there is no trouble codes. If a coil was weak would that throw a code?.
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Old 07-16-2016, 10:26 PM
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Re: Rough Idle & Stumbling

A weak coil itself will not throw a code, but as soon as it starts misfiring, you will get a P030X code (X = cylinder).
Did you check for any vacuum leak at the intake? Maybe a disconnected hose or dried out hose, which leaks?
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  #10  
Old 07-17-2016, 12:10 AM
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Re: Rough Idle & Stumbling

Quote:
Originally Posted by Frango100 View Post
Did you check for any vacuum leak at the intake? Maybe a disconnected hose or dried out hose, which leaks? [/FONT]
Spray your vacuum lines with carburetor cleaner or WD40 with the engine running. If the engine speeds up while you are spraying, you have found a vacuum leak. It's best to use a nozzle extension so you narrow your spray pattern and you won't have quite the mess to clean up afterwards.

Another tip just struck me. There is nothing in the world better to clean and shine under hood plastic and rubber parts than GOJO. (Not the kind with pumice, use the soft stuff) Your plug wires will look brand new. GOJO and a rag are all you need.
Once you get your wires clean, run a screwdriver along each of your plug wires with the engine running and if you see spark jump to the screwdriver you have a bad plug wire. You can also check them with an ohm meter if you have access to one. YouTube will have videos.
I'm not as familiar with these new cars as I am the ones with carburetors and the word Magnum in the engine name ( and 340 or 440 in there somewhere) so pardon my ignorance. If your engine has a distributor cap and rotor button check those too. With over 300000 km on it I would be sorely tempted to do a complete tune up and go from there. Plugs, wires, distributor cap, rotor button, and fuel filter. Since you haven't had it long and you're not familiar with its maintenance history it will at least give you a starting point for future maintenance.
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  #11  
Old 07-17-2016, 09:26 AM
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Re: Rough Idle & Stumbling

Also, since the seafoam seems to be helping, i would do a full treatment. Let a half bottle of seafoam go slowly into the brake booster vacuum line and shut the engine off (do this at normal operating temperature), to let the seafoam soak. After half an hour start the engine again and drive it. Lots of smoke will come from the exhaust, so do this at an appropriate place, to not get angry nabours.
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  #12  
Old 07-17-2016, 12:27 PM
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Re: Rough Idle & Stumbling

I picked up a cheap can of carb cleaner and checked all the vacuum lines, base fo the throttle body and intake gasket. Idle never changed so I removed the breather hose from the throttle body cover and sprayed into the cover to see if the cheap stuff would cause an idle change. What that did was the smooth out the engine and that lasted a few minutes until the vibration returned but less than before. From that it suggests to me the problem lies in one or more of the injector(s) since the carb cleaner basically added fuel to all the cylinders. I put some Lucas cleaner in the tank and filled it up once again. When the problem arose I had put in the Lucas cleaner but added too much gas. That did seem to help it a little so I'm going to run it a few days and see if it clears up.
Thanks for all your help and I'll let you know how it's going in a few days...
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