97 4 cyl rough idle 45 seconds after start - JeepForum.com
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post #1 of 28 Old 04-04-2006, 01:14 PM Thread Starter
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97 4 cyl rough idle 45 seconds after start

I have a 1997 4cyl, 5 spd, ac/ps, etc. Whenever I start the vehicle, cold or warm, between 45 seconds and 50 seconds from start, the engine will begin idling very roughly, and almost die. I must rev the engine to about 2500 or 3k three to four times, then it will idle normally and operate correctly.

If I start the vehicle and drive away immediately, or even after 30 seconds, it will begin to sputter and run roughly ALWAYS from 45 to 50 seconds after start.

I'm thinking that this is a sensor which kicks in at 45 to 50 seconds after start (TPS?), but am unsure which one. I can deal with this anomaly, but it's my wifes' DD, and she doesn't like the hang time.

I have removed the TBI and cleaned all the detrius that was included from the prior owner, but I did not remove the sensors. I cleaned with carb cleaner as well as possible.

Your assistance is, as always, greatly appreciated.

Harry 61, San Angelo TX

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post #2 of 28 Old 04-04-2006, 04:06 PM
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I've got the same year and model and mine does the exact same thing, I have been unable to figure out the cause, if you ever find anything out let me know. thanks
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post #3 of 28 Old 04-11-2007, 11:35 PM
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I have this EXACT same problem with the TJ I just bought, somebody has got to have found a problem to this!


Red 1992 Jeep Wrangler - 2.5L/5spd, lifted 4" sitting on 33s
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post #4 of 28 Old 04-12-2007, 01:01 AM
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I also have the 2.5('99)

Clean the IAC, O2 sensor (top one) and TPS thoroughly with electornics-type cleaner and see what happens. Fixed it for me...

Oh yeah, and then disconnect the battery for 10 minutes and ground it. If thats not it, I have no idea.......
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post #5 of 28 Old 04-12-2007, 01:34 AM
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I know that Chris had some similar problems on his 98 TJ, it was starving for fuel due to a clogged fuel filter/strainer at the bottom of the tank. When he removed and replaced the filter, the problem was gone.

I dont know if that helps you or not. They say that the strainer is supposed to be a lifetime thing, but his was totally choked with dirt and grime. Id imagine alot of fuel problems could be associated with it.

Good luck in diagnosing your problem.


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Last edited by JeepGal; 04-12-2007 at 01:45 AM.
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post #6 of 28 Old 04-12-2007, 02:14 PM
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mine always did this - until i installed a new motor.
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post #7 of 28 Old 04-12-2007, 10:20 PM
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I have a 97 TJ with a fresh 2.5 and it does exactly the same thing. Mine started doing this after I removed the cat and installed an 02 simulator. I welded a bung on the exhaust and bought a new 02 sensor (lower) and it made no difference. I did notice that turning the key on and waiting a minute or two for the 02 sensor to heat up made a difference. I'm going to try a new 02 sensor (upper).
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post #8 of 28 Old 04-13-2007, 09:08 AM
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Mine doesnt have a cat (bought it like that) and it runs perfectly with the lower O2 sensor unplugged....only the check engine light stays on.

A mechanic friend of mine advised me to always take 5 minutes and clean the O2 sensor before replacing it.... may save you some $$. Has worked for me...
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post #9 of 28 Old 04-14-2007, 09:44 AM
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It's worth 5 minutes to save $70. I'll try anything at this point.
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post #10 of 28 Old 04-15-2007, 03:56 PM
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My 98 would run bad and throw code for TPS , clear code would run alright for a while , after 3rd or 4th time replaced it, has run great since.
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post #11 of 28 Old 05-26-2007, 08:56 AM
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97 4 cyl rough idle 45 seconds after start

I have the exact same problem also. After about 30-45 seconds sputters/stalls almost or does die, hot or cold doesn't matter. After that runs perfect. This is dangerous for my 17 year old to drive. It has had a new engine put it in and has only a few miles on the new engine, had the problem before the engine and has it now also. New plugs, wires, distributor cap, ran cleaner through it checked codes etc. Nothing. Does it without fail. Tried leaving the key on before starting to build up fuel pressure too, no difference. I've about had it with this Jeep. Worst vehicle ever owned.

97 2.5L with automatic transmission 90,000 miles

Which would be best to try first, anyone else seen this problem and solved it? From the forum I've come up with this:

Fuel pump (wouldn't it do this all the time?)
Fuel filter (restricted flow would be all the time)
Front O2 sensor
Already did the plug, wires, distributor cap, new engine (because of cracked piston at 90,000 miles)

Any ideas? Desperate, ready to get rid of it. I can't believe this is not solveable.

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post #12 of 28 Old 05-26-2007, 10:01 AM
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Sounds like I'm in the same boat as you!! I just bought a used motor to go into mine due to a cracked piston as well. (2.5L, actually broke the piston skirt all the way up to the wrist pin, caused some major scaring of the cylinder wall, not happy....) Anyways mine used to do the same thing every time I would start it, and one day it finally threw a code. I plugged in the scanner and it was "P0135: O2 heater malfunction" so I called a friend and he said to replace the O2 sensor, and I said which one, and he told me its probally the upstream one (closest to engine) because that one is the one that does most of the reading. So I swapped it out, and problem solved. Plus I got 30-40 miles per tank now due to that dead O2 sensor.
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post #13 of 28 Old 05-26-2007, 10:17 AM
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My 97 does it, too..... I try to just start up and let idle for about a minute, if I can, or I just coast out of the driveway down to the street, that usually gives it enough time to get it over with..... I wish I had a nickel for everytime I have read "changed the o2 sensor".... why do they go out all the time?

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post #14 of 28 Old 05-26-2007, 10:52 AM
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Count me in, Same exact problem 97 4.0L. Cannot afford new O2 sensor yet. Waiting for new exhaust first. Changed TPS, cleaned ISSM, Bought tools to check fuel system. I hope its the O2 sensor. I've been chasing this problem for a year. Lots of people have this problem. Q-01 can you provide more details on cleaning the O2 sensor. Or how to check it with an ohmmeter? I was under the impression they were very sensitve and shold not be messed with.

Jeep took another piece of my finger today...
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post #15 of 28 Old 05-26-2007, 03:22 PM
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I have 97 4cyl, same early sputter issue. I replaced my TPS with one from NAPA. Cured the problem.

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