1997 Wrangler TJ 4.0 engine sputtering

[Michael Polasek]

I've read through the forums on this topic, but still can pin point my issue. 1997 Wrangler TJ 4.0 with only 84K miles. I'm experiencing sputtering, erratic rpms that drop below 1k when started, it's like it's running out of gas. When I start to drive it, sputters, lack of power, cuts out, and I have to feather the accelerator to keep it driving. I've experienced this before, but rarely drive the Jeep. I replaced the plugs, distributor cap/rotor, cables, tps, tried fuel injection cleaner, fuel pump and filter, cleaned the throttle body and just replaced the upstream O2 sensor, yet problem still exists.

I've read to replace the plugs again, could be a crack, try to replace the coil rail. The killer is I've gotten no codes thrown in the past nor present. I'm at a loss. Any thoughts or ideas as to what's going on?

Thanks!

 

[Jerry Bransford]

Confirming new fuel pump right? I dunno for sure but the only thing you haven't changed that is a potential source of problems is the ignition coil. If you replace it avoid store brands or "high-performance" crap ignition coils. Before I knew better I replaced my OE ignition coil with a "performance" version and it completely crapped out while 40 miles from nowhere in the middle of the desert.

 

[Michael Polasek]

Confirming new fuel pump right? I dunno for sure but the only thing you haven't changed that is a potential source of problems is the ignition coil. If you replace it avoid store brands or "high-performance" crap ignition coils. Before I knew better I replaced my OE ignition coil with a "performance" version and it completely crapped out while 40 miles from nowhere in the middle of the desert.

Yes, new fuel pump assembly about 5K miles ago. Frustrating no codes being thrown. There's only 1 upstream O2 sensor on the 97 TJ? Happen to know how many? Curious if I maybe have another bad one? Coil replacement will be next and may have to replace all plugs and cables, rotor/cap again while at it....pain in ass. What brand would you recommend? Thanks Jerry!

 

[jrmcafee]

This sounds like exactly the same issue I’m trying to address right now. @Michael Polasek did you resolve yours?

 

[Michael Polasek]

Hey man, my issue is resolved! So I replaced the crankshaft sensor, O2 sensor, IAC, TPS, and MAP on my throttle body, but unplugged them first while running to see if it still stalled, which it did. Got tired of trying to troubleshoot on my own and suspected a fuel related issue. Took it to a Jeep shop, ran a fuel pressure check and sure enough, significant drop in pressure. Turns out it was the fuel pump assembly again!

So, the last place I had it replaced less than 3K miles ago, actually NEVER replaced it, malfunctioned, or it was a defect. After speaking with the shop mgr he said it can gum up if I'm not driving it or at least starting it every week. It has sat for a month or a bit longer before I even start it at times. Said I'd be right back here if I didn't run it once a week. Just glad the problem is resolved and it runs like a top! Now on to the next issue, fan/ac/heater stopped blowing :-0 Never ends.....

Save yourself a headache and just go get a diagnostic run at a reputable Jeep only shop if you can.

This sounds like exactly the same issue I’m trying to address right now. @Michael Polasek did you resolve yours?

 

[jrmcafee]

Hey man, my issue is resolved! So I replaced the crankshaft sensor, O2 sensor, IAC, TPS, and MAP on my throttle body, but unplugged them first while running to see if it still stalled, which it did. Got tired of trying to troubleshoot on my own and suspected a fuel related issue. Took it to a Jeep shop, ran a fuel pressure check and sure enough, significant drop in pressure. Turns out it was the fuel pump assembly again!

So, the last place I had it replaced less than 3K miles ago, actually NEVER replaced it, malfunctioned, or it was a defect. After speaking with the shop mgr he said it can gum up if I'm not driving it or at least starting it every week. It has sat for a month or a bit longer before I even start it at times. Said I'd be right back here if I didn't run it once a week. Just glad the problem is resolved and it runs like a top! Now on to the next issue, fan/ac/heater stopped blowing :-0 Never ends.....

Save yourself a headache and just go get a diagnostic run at a reputable Jeep only shop if you can.

Good on you mate. Ive replaced the same items with the exception of the IAC (which I cleaned thoroughly). My shop did a fuel pressure test because they suspected the pump. Funny thing is it’s cranking and running fine. Only time it bogs and fails is if I add any throttle after a cold start. After about a minute running it does fine.