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i have a1999 jeep wrangler, was running fine. i took the battery completely out. now it is running terrible. Answered

computer says it is tps. why now would it mess up. tried disconnecting neg battery post for 1 hour, but no help. what can i do next? idiling low, no power uphill or giving gas cuts engine out. please help

3 Replies

canucksgirl (author)2012-10-09

This is a fairly common problem (for MANY vehicles), and although you have symptoms of a Throttle Position Sensor problem (and likely trouble codes), I'm 99.999% sure the problem is NOT the TPS.

When a battery is replaced, there is usually no problems, but once and awhile you can get rough idling, stalling and a lack of power when the vehicles computer (PCM) is reset. When this happens, all the data from sensors that the computer has stored is lost, including the natural engine idle speed. (It's like losing all your stored radio stations and clock).

So when this happens, the PCM has to "relearn" the idle properties. To speed this process up, you'll want to start the engine and warm it up; giving it a little gas to get the engine idling normally. When the engine is completely warmed up, let it idle for about a minute and then turn on ALL your accessories (lights, radio, AC, heater etc) and let everything run for another minute or so. Then shut off all the unneeded accessories.

Now you'll want to run the vehicle for about 30-40 miles, so make sure you have enough fuel. During the running time, make sure you cycle through all the gears and periodically pull off the road and just let it idle for a minute or two. If necessary, assist the idle by holding the brake and giving it a little gas. During this process, the PCM will recollect all the data it lost and should start running like it did before you replaced the battery.

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Burf (author)2012-10-09

The symptoms you describe are typical of a throttle position sensor problem. I suggest you trouble shoot the TPS and see if you can determine what is going on. It could be anything from a loose electrical connection to a unit failure.
You can find guides to trouble shooting your particular vehicle on the internet.

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