atteburyc

Hey jeepers 98 4.0 auto trans Cherokee sport. I left home this morning for an interview when I was accelerating down gratiot the Cherokee decided it didn't want to shift into second. This isn't the first time it's done this and is usually between 1-2 and 2-3..... So when it does this there is no response from the gas pedal in fact the rpm's drop down to around 200 and will bounce between 200-400 until the jeep eventually dies. I'm in the process of changing out my trans fluid but I didn't think that dirty trans fluid would make the jeep idle rough and eventually die. Could a bad tps cause this? Any help would be appreciated. A mech down the street told me Bad cat, mine is free flowing so I ruled that out. Sorry for the term paper thanks for any help.

VTJeep

I'd lean more towards a sensor or computer- starting with the o2 sensors, the TPS, IAC valve.. Have you hooked it up to a code reader/diagnostics machine? Even if the CEL isn't on, there may be codes stored in there that may give you a direction. I've had an unfindable issue with the o2 sensors voltage being way off sine I bough the thing 7/09. It will suddenly bog down, buck, chug and pop (backfire) at manifold. Thought it was fuel delivery issue, it was, fixed it, problem continues intermittently.. I'll post the heel outta it when I figure it out!

atteburyc

I do have two CEL both for the downstream o2, over heated, and shorted to circuit. I have cleaned the iac and connections for the tps but have to a search for the tps testing procedures because that's next on my list. My problem does sound a whole lot like yours I'll also keep this updated.

salad

Woah. Yeah you should really check out the O2 sensor and its wiring. It can cause all of those problems since it is used by the computer to determine fuel delivery

tannerp89

put a new downstream O2 on it. should fix the issue.

atteburyc

I always thought the downstream o2 sensor was purely for emissions and thats it's reasoning for being in or after the converter. I have replaced it anyways with an ngk? O2 from napa no codes for the first o2 sensor though.

atteburyc

I always thought the downstream o2 sensor was purely for emissions and thats it's reasoning for being in or after the converter. I have replaced it anyways with an ngk? O2 from napa no codes for the first o2 sensor though.

ZINGGG

Wait so you've replaced the downstream o2 sensor (the post-cat sensor) and you are still getting that code? Did you clear the code and it came back even after replacement?

atteburyc

I had replaced the sensor previously and am finally posting about the issue. The codes were cleared after I replaced it and yes, they came right back. I just got it scanned at autozone twenty minutes ago and got high voltage to bank one sensor one and the original two that have been there for the downstream sensor. So I'll start with replacing the upstream and checking the wiring. Probably tomorrow though.

salad

Oops sorry, typed that at lunch on my phone and didnt see the "downstream" part. You're quite right, that should only cause a blinky light. I'd look into wiring for sure. I suppose ECU if that foesn't get you anywhere

atteburyc

Okay I was up early driving around to try and figure this out, and here's what I've learned. The downstream codes always come back on almost immediately after I clear them. However, the only time that the code for the upstream sensor(high voltage) appears is after my issue occurs. So when my broke *** gets paid friday I'll be replacing the upstream with an NTK from napa.

VTJeep

Your right to replace the other o2 sensor. Generally with these guys, it's like spark plugs- gotta do the whole set.. But either way, get OEM! Idk if the NTK's are, I think it's Bosch, but whatever.. I've had bad luck with online parts like TPS and IAC valve, but going thru the parts store is legit.

I hope this fixes the issue. The issue may not be the o2 sensors, but a short or issue with another computer or sensor. Idk, not to be pessimistic, but just from experience..

salad

Bosch is the OEM for RENIX years, 91+uses NTK. I believe the part number for upstream O2 is 23151

atteburyc

Well I hope it works, but yes... I'm not getting my hopes up on a simple fix. When I replaced the downstream, which was a week after I bought the jeep, it looked like the wiring for the old sensor was grabbed by the drive shaft and it ripped it right off of the sensor and probably caused some electrical issues which I'm now dealing with. So when/if this doesn't fix it I'll be spending my days messing with wires.

atteburyc

Just an update. It was the upstream oxygen sensor. There was actually an exposed wire on the Bosch sensor I bought not more than five months ago. Replaced it with an NTK, $36 from rock auto or $75! from napa... Replaced the heated oxygen sensor fuse, (15a) that kept popping, and I haven't gotten the jeep to act up again. Problems solved, for now.