Stumbling, Possible Sensor Issue?

97' 5 spd

Every so often the Jeep will stumble (feels like loss of power) after about 2 mins of driving. Giving it more gas doesn't help--rpms do not go up. However shiting up into a higher gear seems to help a little. So it will stumble for a few seconds, clear up and then it runs just fine. Stumbling happens both when Jeep is cold or hot. Seems to happen more often after I have driven it somewhere, parked, and then restart it a little later.

Any ideas? I have replaced air filter, cap and rotor, ignition wires, spark wires, and cleaned out throttle body. Really no difference. Thanks!

Replace your o2 sensors. Had same problem but I could floor the gas and it would pop and then take off like nothings wrong. Only happen when it was warming up and only happened for a couple of minutes.

Has anyone out that had this problem and solved it?

I have been trying to track this down forever, and I think it may be related to my poor gas mileage. I have replaced O2 sensors and TPS to no avail.

ANYONE???

Hold on, quit throwing parts at it. They have a scan tool port for a reason! Go get codes pulled or pay somebody a little bit for diagnosis. It's a lot cheaper than replacing everything.

IS EVERYONE HAVING THIS PROBLEM THIS WEEK?
im having the same problem with my 2.5L.

where do you get a scan tool? and how much does one run?

more importantly, where do you hook it up, and can you use it on an '85.

The code readers AutoZone uses for free work on 96 and up. 85's not going to have all that much diagnostic functionality.

JJacobs said:

Hold on, quit throwing parts at it. They have a scan tool port for a reason! Go get codes pulled or pay somebody a little bit for diagnosis. It's a lot cheaper than replacing everything.

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Not every problem will show up on a scan. In particular fuel delivery problems will not set any code at all, and many mechanical problems will not either. Clogged or worn injectors, stuffed fuel filter, weak fuel pump, vacuum leaks, bad spark plug gap, all fly under the radar.

Not really, they'll set lean codes, P0171 and 0174 on an OBD2 vehicle. I agree in part though, not everything will show up- but if the test is free for the taking at the parts store it's the best place to start.

JJacobs said:

Not really, they'll set lean codes, P0171 and 0174 on an OBD2 vehicle. I agree in part though, not everything will show up- but if the test is free for the taking at the parts store it's the best place to start.

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I certainly agree that you should get a reading first. It's true that if these conditions are bad enough, and consistent enough, to require correction by the PCM, they might result in a code. However, they are not directly monitored, and if intermittent, they may never show a code. The 99 FSM specifically mentions the following non-monitored circuits: Fuel pressure;secondary ignition, cylinder compression, exhaust system, fuel injector mechanical functions, excessive oil consumption (well, that one should be obvious);throttle body air flow; vacuum assist, (unless it screws up the MAP reading); poor PCM ground, and other bad PCM connections. Remember that it's possible too for a sensor to be within range and still not be operating correctly.

A lot of things that aren't explicitly monitored by the pcm will end up throwing codes in other ways. For example while cylinder compression is not on the list directly, a clogged injector, weak rings or valves, or ignition problem will all end up generating a misfire code. I've seen lean codes caused by weak pumps, tired relays, bad MAFs, vacuum leaks, etc. OBD2 is great for alerting you to general problems but it can take some leg work to really nail the problem down.

A lot of our customers think the 'computer' (scan tool) knows exactly what's wrong and get mad when we charge diagnostic fees. If only it was that easy.