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Discussion Starter · #1 ·
1998 TJ 4.0. Consistent, recurring problem. No engine light - no codes stored when scanned. Occurs hot or cold. Starts fine. Runs fine out of the driveway, parking lot, etc. Half a mile up the road: if stopped, the idle drops to almost stall speed; if moving, I lose power, and the Jeep bucks, backfires, and generally behaves poorly. This resolves after a moment or two. The Jeep runs fine after that (with hard acceleration and every other condition I can imagine and employ). I cannot get the issue to repeat unless, of course, I stop somewhere and turn off the engine. Then it's Groundhog Day.

I replaced both the TPS and the MAP sensor. This fixed the engine surge at idle that went with the above symptoms.

First test drive went great. Next time out, it's back.

Help?
 

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Discussion Starter · #5 ·
My work vehicle, so I have little choice but to fix quick. Actually got 10% off reserving online. Thanks for trying to save me some $.
 

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That very well could be caused by a bad Throttle Position Sensor. Those symptoms have happened on both my previous TJ and my wife's Grand Cherokee and both were from a bad TPS.

That is happens even when cold rules out the 02 sensors since the 02 sensors are ignored until the engine has begun to warm up.
 

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That very well could be caused by a bad Throttle Position Sensor. Those symptoms have happened on both my previous TJ and my wife's Grand Cherokee and both were from a bad TPS.

That is happens even when cold rules out the 02 sensors since the 02 sensors are ignored until the engine has begun to warm up.
He started by saying hot or cold, but then went to say that it was fine until he drove it up the road, which is why I thought O2 sensors, due to the fact that they don't affect it till it is warmed up a little.
 
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