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jeepguy97 06-10-2011 09:59 PM

97 TJ 4.0 sputters, almost dies
About a week ago my 97 TJ (4.0) with 121K miles started sputtering in 2nd gear going at constant speed (20-30 MPH). Very random, and no check engine lights. Put in some fuel injector cleaner, replaced plugs/plug wires, dist cap/rotor and took it for a ride tonight, and it is still doing it. It runs just fine for a long time, does it once for a few seconds, then runs fine again for a long time There's no consistency to it at all.

Anyone seen this before, or have any ideas? Read on a different forum that someone experienced a similar problem and it ended up being an O2 sensor, but if it were that I'd expect the CEL to light up and that's not happening. Any help is appreciated.

smoke5643 06-10-2011 10:25 PM

Well I guess no need to start a new thread. I just bought my first Jeep a 97 TJ 4.0 Tuesday. After 2 test drives, 2+ hours continually driving on the way home and about 5 more trips totaling an hour on Tuesday mine started acting similar to yours. At low rpm's especially in 2nd and 3rd or at a pull/low rpms in 5th I noticed sputtering, bucking and rough idle after warm. I did however get a P0132 code last night (Pre-Cat O2 sensor malfunction) and replaced it after about 3 hours of muttering things under my breath (starting threads where gone, had to retap). Cleared the code took it out for a spin and in the 3 miles I drove it (started raining about 1.5 miles after I left the house with the top off) the problem of nearly dying was subdued although cant say totally gone as I didnt drive it enough. Did notice however that at constant rpm's the engine feels like it is "missing" and idle is still a little rough again like its "missing". Already got fuel injector cleaner in a new tank and it looks like the plug/wires/dist/rotor swap is in the works for next week.

I will add that mine was fairly consistant after it started acting up. It would do it every trip I made in it. I did however notice that if I revved to 2800-3000 before shifting, it wouldn't do it but when I got to speed and went into 5th it was still there especially on a hill or trying to accel in 5th.

From what I have read by "Googling" this seems to be a fairly common problem but with a fairly wide variety of fixes. From plugs to o2 sensor to other sensors to bad gas to too many others to remember. Anybody have any insight for us? As OP said all help is greatly appreciated.

BTW mine has 104000 with stock everything that I can tell (besides tires of course).

Shelby427 06-10-2011 10:41 PM

O2's are notorious on jeeps. At the those kinds of miles if one goes bad, you are better to replace all. Do not use Bosch, they don't agree with jeeps.

One of the other biggies it the fuel pump. Don't know what Chrysler was thinking with no fuel filter and just using a sock in the tank. But at your miles a pump could be a culprit.
They will do all kinds of acting up before they finally die. Can cause missing,sputtering, stalling, and so on, then they clear up and work fine again.
Will act up more so hot.

Having the fuel pressure checked with a gauge can often pick it up.

Also in the list can be a Crankshaft sensor, or a Throttle Position sensor. They can sometimes act up and not throw a code.

Both can be checked with an ohm meter. The crank sensor should read 200 ohms, +/- 75. The TPS, as it is turned, the ohms should climb in one direction, and fall in the other.
Readings should be smooth and gradual. If it skips a spot, or jumps in the readings it's bad.

The TPS would be more likely at fault with the descriptions listed, then the Crank sensor.

smoke5643 06-10-2011 10:46 PM

Wow wish I would have posted this yesterday... I used a Bosch as I have always had good service out of them lol. What kind of problems out of it should I expect? I REALLY dont want to try and replace it again.....

smoke5643 06-11-2011 11:12 AM

Also, any suggestions on brands as far as the plugs/wires/dist cap/rotor go and what kind of a pain would the fuel pump be to replace? I assume factory for the fuel pump. Just trying to cover all my bases as I just got this thing and I LOVE driving it but the engine not running right is annoying the piss out of me lol.

Jerry Bransford 06-11-2011 11:41 AM


Originally Posted by Shelby427 (Post 1297577)
Don't know what Chrysler was thinking with no fuel filter and just using a sock in the tank.

The TJ actually has a superb and very long lasting (lifetime) fuel filter inside the fuel pressure regulator. Made from an extremely fine material that is much like a dense felt, it has a physically huge surface area that is good for the TJ's lifetime. The type of fuel filter now used in modern vehicles like the TJ is superb compared to the old glass inline filters cars had when I was young that had to be regularly removed and cleaned or replaced. :)

Old Grunt 06-11-2011 01:22 PM

FWIW have who ever your local 'real' mechanic is take a look at and put your coil in a test stand or a portable diagnostic unit. For as small as it is, this one unit can drop your Jeep dead in it's tracks for no apparent reason at any time. Mine went dead at 135K at the local Recycle center, thank god. Had it hauled back to my guy who spent about an hour tracking the wiring and electrical circuit's. When he got to the coil he noticed it had 2 hairline crack's in it, 1 along the side and another at one of the bolt hole's. He replaced it and it started it up PDQ. Turns out when my daughter drove the Jeep she tried to do a u'ey and wound up nose deep in a drainage canal. Thinking 'It's a Jeep is a Jeep is a Jeep', she tried to drive it out. It did but she almost racked the frame and suspension like a spaghetti dinner. My mech. tells me that was probably when the coil started to corrode. it just took time for it to finally open up to rain and weather. When it did, well, there I was. So look at the coil. It's an easy fix for about $50.-- and 10 minutes of swapping it out.

jeepguy97 06-15-2011 09:54 PM

Thanks for the tips everyone. Out of town now but drove it all last weekend and had only one minor incident where it started to sputter. I was leaning toward replacing the O2 sensors next but didn't think about the TPS, will have to consider it also. I wish it was less random so I could know when I really have it fixed.

jeepguy97 07-07-2011 08:02 AM

Thanks everyone for the tips. I think I've figured out what my problem is. It started happening more frequently, but I noticed it only happened right after starting it up and usually within the first 1/4 mile of driving. I suspected the upstream O2 sensor was going bad, but wasn't bad enough yet to trip the CEL, so I disconnected it about a week ago. It's run fine ever since. Looks like I'm going to the store to buy a new O2 sensor.

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