2.5L sputters unless at WOT or closed throttle

_Kevin · 07-27-2010, 11:23 AM

I had this problem a while ago, thought it was an exhaust clog, and replaced my cat. I figured it was 13 years old, so after all those years it had just internally began to fall apart and clog itself. After replacing it, my Jeep was back to normal for several months, and now is sputtering again. If I'm at wide open throttle (full pedal), or closed throttle (no pedal), it's fine, but as soon as I'm somewhere in between it sputters and loses power. The RPMs seem to fall slowly while doing this, so it's not like it's popping in and out of gear. Does anybody have any ideas as to what's happening? Any suggestions as to how to fix it? I was thinking of replacing my muffler now, maybe the damaged cat damaged the muffler as well? It's a FM44 I bought off a member here, so it's had some use, but isn't ancient like my cat was.

Besides the sputtering, it's also been pretty rough at idle lately, which I'd assume is connected to whatever is causing the sputtering

_Kevin · 07-27-2010, 01:40 PM

Bump

_Kevin · 07-27-2010, 10:09 PM

Bump

**MO2500** · 07-27-2010, 10:57 PM

When is the last time it's had a tune-up? Spark plugs, cap & rotor, air cleaner etc? I would suggest starting there if it's been awhile since they've been changed.

Mine was sputtering and idling rough when i bought it and changing the plugs fixed it. The gaps had opened way up on the old plugs causing the sputter and rough idle. Running Autolite AP985's now and it has been running great since

Also, try cleaning the throttle body, (MAF) mass airflow sensor and (IAC) idle air controller

_Kevin · 07-28-2010, 11:31 AM

Thanks, I recently replaced the plugs and wires, and the cap and rotor aren't too old either, but I'll clean out the TB and air filter. I'm running the same plugs as you, big difference from the older plugs it had since their gaps were pretty open

**MO2500** · 07-28-2010, 11:57 PM

Also, have you tried the "key-on,key-off,key-on,key-off,key-on" trick to see if the computers displaying any codes?

_Kevin · 07-30-2010, 09:25 AM

The first time it happened before I replaced my cat it didn't throw any codes except for an O2 sensor and battery disco, I'll run it again today though. Yesterday I put in some fuel system cleaner, today I'll clean the TB and replace my PS switch (It's been throwing codes, and supposedly kills O2 sensors)

_Kevin · 07-30-2010, 11:51 AM

12. Battery disconnected recently
21. 02 Sensor (Upstream, downstream, and left are all listed under 1 code)
51. Fuel system lean
65. Power steering switch failure (Just replaced it, guess the computer hasn't gotten a chance to reset yet)

AEagle326 · 07-30-2010, 11:53 AM

how old are the 02 sensors? that could be the issue

**MO2500** · 07-30-2010, 12:04 PM

Yea it most likely is a O2 sensor feeding the computer false information. It may be causing the engine to run lean when your cruising but richen up and run alright when your under load (WOT). I'm not sure how you go about testing which one it is or if one is in fact bad though.

_Kevin · 07-31-2010, 11:54 PM

Damn, ok. Thanks guys, I guess I'll just have to replace all the 02 sensors when I get a chance.

Rio_Grande · 08-01-2010, 09:57 AM

You are on the right track, but before just replacing the o2 sensors, (no need at throwing money at good parts) Unplug your front o2 sensor and drive for a bit. if the issues improve then I would buy a front sebsor. There are some threads here on this, seems to be an effective way to test the front o2. Good Luck.

_Kevin · 08-02-2010, 10:28 AM

I'll definitely keep that in mind, thanks a lot