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Old 06-22-2011, 12:32 PM   #1
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Question Accelerating Problem

This problem started about a month ago after I fixed my motor mount. When I start to accelerate heavily my jeep starts to die and backfires. Sometimes the jeep starts to run normally again or it runs worse. It mostly happens when I go uphill. I've recently changed my TPS, fuel filter, fuel pump, spark plugs, and o2 sensor.

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Old 06-22-2011, 12:47 PM   #2
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Quote:
Originally Posted by DaveO94
This problem started about a month ago after I fixed my motor mount. When I start to accelerate heavily my jeep starts to die and backfires. Sometimes the jeep starts to run normally again or it runs worse. It mostly happens when I go uphill. I've recently changed my TPS, fuel filter, fuel pump, spark plugs, and o2 sensor.
I'm on my phone I can't see your profile what engine do you have 2.5 or 4.0

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Old 06-22-2011, 02:13 PM   #3
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2.5 liter
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Old 06-22-2011, 03:25 PM   #4
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Knock of a vacuum line?
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Old 06-22-2011, 09:39 PM   #5
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All the vacuum lines I can find are connected properly. I'm doing an oil change tomorrow because it's time do you think that would help
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Old 06-22-2011, 09:58 PM   #6
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you did a lot of things, how about resetting the ECM and I would go back and re check everything. Plugs seated properly? Every thing is connected right.
Why did you replace those parts, to fix the problem? Was it just a coincidence it after
You replaced the mount, or did it happen because something was done that could of caused it? Need a little more information
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Old 06-22-2011, 10:12 PM   #7
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If it idles fine and runs okay with light throttle. But has no power when you step on it and runs like crap. Have the cat checked or you can disconnect the cat from the pipe and go for a ride.

One other thing that has happened in my shop was I had a car come in with no power on heavy acceleration. But ran fine at light throttle. Ended up being a broken plate in the muffler on that one. Under heavy acceleration the plate would block the exhaust hole and wouldn't have any power. It would also pop and back fire.

Just something to think about. Lets us know what you find.
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Old 07-08-2011, 12:42 AM   #8
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Sorry about not getting back to anyone but I don't have a cat and the muffler is 2months old. I changed the distributor cap and rotor and I got new spark plug wires. Nothing has helped and the jeep actually runs worse everytime I replace something.
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Old 07-08-2011, 01:02 AM   #9
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I am far from an expert, but my $0.02 is from what I have read on here in the past so I'm going to throw in Ignition coil, crackshaft position sensor, IAC valve or something close to do with ignition timing. If its backfiring then excess fuel is running into your exhaust system and igniting with the heat instead of in the chamber, so I'd say something is wrong in terms of when you hit the gas you get more fuel and not enough ignition,almost like the engine is drowning.

Again I am really new to the jeep life and am just saying what I have understood so far, please correct me if I'm wrong, but its a start.
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Old 07-08-2011, 01:25 AM   #10
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What's an IAC valve? I changed my igniton coil over the winter and I plan on getting some sensors if I can afford them.
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Old 07-08-2011, 11:40 AM   #11
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I replaced my motor mounts a couple weeks ago and noticed that one of the vacuum ports is capped off. The cap was in pretty bad shape and fell apart when I rubbed my arm against it. You might check that and the vacuum line that goes to the map sensor. The factory lines are normally pretty much shot after they get this old, the plastic gets brittle and the rubber starts crumbling. If all is ok there, I would suspect a bad map sensor.
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Old 07-08-2011, 12:02 PM   #12
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I have the same exact problem! But my jeep is a carburator engine, so if yours is too, then it is most likely your carb. This problem is very consistant, but the only thing that helps me is carb cleaner. When it gets really bad and when i know im driving up a hill and questioning if i can make it, i just stop and spray some carb cleaner that eliminates the problem for 5-10 minutes.

I have to remove the entire carb and thourally clean it and possibly replace it, but im just too busy and lazy.
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Old 07-08-2011, 01:14 PM   #13
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I have a throttle body which is basically the same as a carburetor. I looked inside it one day and it has a little bit of build up on it. Would cleaning it be hard
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Old 07-08-2011, 01:27 PM   #14
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find the post about the 2.5 jeeps with this kinda problem your having. the ECM probably has burnt out resistors in the ECM. Check out to see if there is a sticky or search around but this is a common problem. And it cause exhactly what your going through.
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Old 07-08-2011, 02:17 PM   #15
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Quote:
Originally Posted by DaveO94 View Post
I have a throttle body which is basically the same as a carburetor. I looked inside it one day and it has a little bit of build up on it. Would cleaning it be hard
well there is 2 ways to clean it... im not a mechanic, but ive looked into this pretty deep so im prety sure this is the only 2 ways to go.

1- go to any automotive store and get a carb cleaner, you open the top and start spraying around in there.. be generious... then start your car let it idle and start spraying again. Then press the gas and continue spraying.. a lot of fumes will be coming out of the exhaust, so make sure its well ventalated and make sure the fumes are actually coming out and your exhaust isnt cloged. This should help.

2- you have to remove the actual unit and clean it with gasoline.. that should be the best thing to use to clean it... if there is a lot of buildup, use a toothbrush or a towel to wipe it off. clean thourally, and again, be generous.. too much gasoline wont hurt... keep cleaning untill its "good as new" then let it sit with gasoline in it this will ensure you got every inch of it.

but try #1 first.. a bottle of carb cleaner should cost you like 5 bucks... definitly worth a shot - i think...
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Old 07-08-2011, 08:42 PM   #16
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if your going to clean the throttle body just go the whole way and take it off to do it. You will need a new gasket which is only $4 from the dealership and a can of throttle body cleaner or as GKjeep said, use gasoline.

Removing it is easy and then just spray the crap out of it to get it clean. The IAC valve is the Intake Air Control valve that is positioned on the side of the throttle body next to the TPS. Take that out too and give it a bit of a spray and get in where it lives and spray that too. If the IAC is still good just be gentle and get it back in nicely. Clean both mating surfaces of the TB and Intake manifold and throw on that new gasket and reinstall the TB.

And its that easy. Check that you have the nipple on the side of the TB and it is still in good shape as they can rot and fall off.

I changed my IAC because it was stock and looked like crap when I removed it but I'm sure there is a way to actually test it.
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Old 07-08-2011, 09:21 PM   #17
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I removed mine and soaked it in seafoam for 8 hours ,it literally looked new afterwards and ran and performed much better.
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Old 07-09-2011, 12:56 PM   #18
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lets look at it this way. the more strain the motor is getting the problem happens. my idea is to check the distributor cap, and or the distributor itself. That is a possibility what is causing the problem and is breaking up when accelerating. Might just be a coincidence that it happened while you did the mount. Also double check the fuel pump/filter. When needing more gas to accommodate the power needed perhaps the pump is not working as it should, and or the filter is clogged. if it runs normal in idle...those are some possibilities to test out.

i moved my timing by mistake once when i hit the damn distributor and it threw my jeep off just like you are saying. possible it was also adjusted in the process. And is off time.
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Old 07-09-2011, 01:34 PM   #19
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Mine did this about 3 weeks ago. I changed my ignition coil, distributor cap, distributor button, plugs, and plug wires. It fixed the problem for me. Good luck bud
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Old 07-09-2011, 01:46 PM   #20
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Instead of changing EVERYTHING at once, why not just pinpoint the problems and change one thing at a time to see what is the actual cause of the problems. Sometimes it is a waste to throw on parts when not needed.
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Old 07-09-2011, 02:06 PM   #21
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try changing your Plugs and wires mine was doing the same thing back firing and all. I changed the plugs and wires and it runs fine now
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Old 07-10-2011, 09:42 PM   #22
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Crank position sensor sounds like the problem. It is on the bell housing on driver side. Broken motor mount and engine movement could have cracked it. That can be a real ***** to figure out. Runs great then sputters and runs like crap sometimes even dies completely but everything you check appears to be fine.
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Old 07-12-2011, 08:52 PM   #23
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Since you're fuel injected you might try checking your Exhaust Gas Re-circulation Valve, and it's accompanying sensor.

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