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Old 01-17-2010, 10:42 AM   #1
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2.5 4 cylinder Questions

I have a 97 Wrangler with the 2.5 4 cyl. engine that isn't running right with a rough idle. When I start the engine (Cold Start) it will idle smooth but after sitting for 30 seconds or so at idle it will start missing and smells rich. I have to hit the gas and bring the RPM's up to "Clear it out". Also when I push in the clutch to upshift or downshift while driving the engine will shoot down to 200-300 RPMS and not come back up to idle RPM's until completely stopped. I'm sure this is something simple but need some help pin pointing the problem..
Added information. My Jeep has 72,000 miles on it and has great oil pressure (Uses no oil)

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Old 01-17-2010, 11:56 AM   #2
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Is the CEL light on?

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Retired my 94 YJ 4cyl 5spd @ 200K
Now in a 04 TJ 4cyl 5spd CV @120K+
Both as a commuter vehicle in NW, NJ
April 2012.downsized and now a 99er.
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Old 03-30-2010, 10:35 AM   #3
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i know this is an old post but i have the same exact problem with my 91 2.5. the only difference is that mine will actually stall maybe 1 out of 10 times. i cleaned the IAC and throttle body and am thinking of using the SeaFoam treatment today. how did you make out with your jeep?
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Old 03-30-2010, 09:13 PM   #4
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Originally Posted by oconnorlandscape View Post
i know this is an old post but i have the same exact problem with my 91 2.5. the only difference is that mine will actually stall maybe 1 out of 10 times. i cleaned the IAC and throttle body and am thinking of using the SeaFoam treatment today. how did you make out with your jeep?
My '99 has a similar issue; at 750 rpm's it idles rough, at 1,000 it purrs. Tried Seafoam a month ago with no improvement. Last week had a mechanic look at it and he cleaned the throttle body and used some professional grade injector cleaner with no change yet.

Still looking for help!
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Old 03-30-2010, 09:19 PM   #5
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Did the mechanic also clean the IAC (idle air controller) that screws to the side of the throttle body? The IAC is what provides all of the engine's air when you are not stepping on the accelerator pedal so it can cause idle problems that go away when you step on the gas a little.
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Old 03-30-2010, 09:28 PM   #6
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I had the exact same problems after tooling around with it a few months myself with no luck and throwing parts and cleaning solutions at it I took it to a omish garage local here. Mind you they have been here nearly 70 years and are very pricey. 90 dollars an hour but there the best around.

I always say you get what you pay for. Ill get him to write me a detailed write up of what was wrong and how he fixed it if your interested!
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Old 03-30-2010, 11:16 PM   #7
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please do!!!!!!
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Old 03-30-2010, 11:19 PM   #8
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I most def will. Ill have it posted for all tomorrow evening!
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Old 03-31-2010, 10:49 AM   #9
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Originally Posted by Jerry Bransford View Post
Did the mechanic also clean the IAC (idle air controller) that screws to the side of the throttle body? The IAC is what provides all of the engine's air when you are not stepping on the accelerator pedal so it can cause idle problems that go away when you step on the gas a little.
Thanks JB. Don't think so. Will look into this. BTW - did you ever get your ride back?
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Old 03-31-2010, 12:06 PM   #10
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BTW - did you ever get your ride back?
Nope, I'm about 99% sure a crooked Mexican law enforcement official is probably driving it around down in Mexico somewhere. To have an American 4x4 with Calif. plates on it is a badge of honor for them.
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Old 03-31-2010, 12:59 PM   #11
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jumping back in here...I did clean the IAC and the throttle body, very thoroughly might i add and it made no change. i tried the SeaFoam treatment and it made not change either. feels like it has a skip at idle and then smooths out if you touch the throttle at all. hope its not a sticking valve or loosing compression. any other thoughts or ideas are muchly appreciated.

p.s. - it always amazes me how many people are on these forums, weather they are for jeeps, fords, heavy equip that are willing and able to helps others...we need more people like them in this country.

thanks again!
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Old 03-31-2010, 01:32 PM   #12
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I had the same problems. Not sticking valves or bad compresion. Im on my way to get the write up now on what was wrong with mine. Paying the shop bill today

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Old 04-01-2010, 05:51 PM   #13
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any luck on the write up form the shop... did they fix the problem?
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Old 04-01-2010, 06:23 PM   #14
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Heres what I got.

1997 Jeep Wrangler SE
150,000 miles
5 speed 2.5 4 cyl

Heres the problem. Had horrible missing, poor gas millage (8mpg), ruff idle, no power, on start up blew black coal dust all over the ground.

Had code PO133 Upstream o2S slow responce.

Shop replaced Front OZYGEN sensor (147.14)
Power steering pressure switch (53.57)

There was a leak in the power steering which was pussing fluid PAST the power streeting pressure switch through the wires into the computer box and other sensors there for confusing the computer and putting oil where oil should never be found thus showing in the exhaust system. Looking like oil ontop of water when blown onto garage floor. It was making the front oxygen sensor maulfunction.

I would not have believed this for my own eyes if they didnt tell me to come down and look at it. They started the vehicle and for sure it was dripping out of the connection as it was running. It was pushing it through my wires to the computer the sensor throwing everything off.

R&R hiigh pressure hose switch
R&R oxygen sensor
Repair wiring at OXYGEN sensor and power steering swithch

They cut the wires and soldered them then wrapped them to keep this from happening again!

Repair power streering pressure switch and oxygen sensor at main computer.

There was also a recal on TJ's in 2006 for a PCM update. Its free. Go do it. If your not sure its already done grab your vin and look it up on jeep or call the stealership.

Tyler

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