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High/wavering idle

Old 08-21-2015, 11:04 PM
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Default High/wavering idle

My jeeps been overheating lately and after messing with a few things I decided to just take my thermostat out completely. At the same time I replaced my harmonic balancer pulley assembly.

Before doing any work my jeep would idle just below 1000 rpm in any gear.

Since doing the work, the jeep idles at around 2000 rpm on cold startup and eventually comes down to around 1500 rpm while idling in park or neutral and the idle will bounce back and forth between ~1300 and ~1600 rpm. It will drop to normal rpm's when in reverse or drive and be steady.

Is this the engine trying to heat itself up because there isn't a thermostat? Or is it something else and simply a coincidence?
Old 08-22-2015, 12:00 AM
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Originally Posted by hockeyfan_83
My jeeps been overheating lately and after messing with a few things I decided to just take my thermostat out completely. At the same time I replaced my harmonic balancer pulley assembly. Before doing any work my jeep would idle just below 1000 rpm in any gear. Since doing the work, the jeep idles at around 2000 rpm on cold startup and eventually comes down to around 1500 rpm while idling in park or neutral and the idle will bounce back and forth between ~1300 and ~1600 rpm. It will drop to normal rpm's when in reverse or drive and be steady. Is this the engine trying to heat itself up because there isn't a thermostat? Or is it something else and simply a coincidence?
put a thermostat back in. Preferably the OEM 195 degree one.
Old 08-22-2015, 12:03 AM
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I plan to when I get a chance. Obviously if the issue goes away then it was the thermostat but I was just wondering if anyone had any input
Old 08-22-2015, 12:05 AM
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Originally Posted by hockeyfan_83
I plan to when I get a chance. Obviously if the issue goes away then it was the thermostat but I was just wondering if anyone had any input
similar problem would happen when u unplug the coolant temp sensor... So I would imagine that with the thermostat gone, the coolant would be too cold and trigger sorta same symptom
Old 08-22-2015, 07:52 AM
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Hmmm. Well guess I'll find out when I put the thermostat back in. Thanks for your thoughts!
Old 08-22-2015, 07:54 AM
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Originally Posted by hockeyfan_83
Hmmm. Well guess I'll find out when I put the thermostat back in. Thanks for your thoughts!
make sure u get the one from dealer.
Old 08-22-2015, 07:58 AM
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I definitely will. The reason I don't have one now is that the replacement one I bought from autozone was defective straight out of the box.
Old 08-22-2015, 08:07 AM
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Originally Posted by hockeyfan_83
I definitely will. The reason I don't have one now is that the replacement one I bought from autozone was defective straight out of the box.
yeah that seem to happen quite often.
Old 08-22-2015, 10:27 PM
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Well for whatever reason today the problem was gone and everything appeared normal. (Still without a thermostat)
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