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Old 07-15-2010, 05:58 PM   #1
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97 4.0 Idle issue

It's not really a rough idle but more like a hesitation/vibration. It starts fine and still has great acceleration. It idles, in park, a bit above 900. I just had the position crank sensor and coil replaced ($356) due to a no start issue. Probably not related but after the two parts were replaced my oil pressure was low when stopped in traffic. Before it was always 40 but now at idle it's just a bit above 0. My jeep was running fine until I replaced a heater hose. Rationally I understand that the issues I'm experiencing now have nothing to do with the hose but... After the hose was replaced the AC died and two days later the jeep would crank but not start and now the weird hesitation. I'm open to suggestions.
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Old 07-15-2010, 06:08 PM   #2
Knows a couple things...

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I think I'd start by buying an aerosol can of throttle body (not carb) cleaner and cleaning the throttle body's interior while the engine runs. The IAC (idle air controller) is bolted to the throttle body and it is responsible for providing all of the engine's air at idle when your foot is off the accelerator pedal.

The IAC does get dirty & when it does, it causes idle problems so that's where I'd start. Make sure some of the cleaner spray gets into the IAC's air passage inlet as shown below. The engine may die a few times while you do this but that does no harm, just restart the engine and keep spraying into the throttle body together with some going into that slot until the can is empty. Stop the engine before the can is empty & use the cleaner with a rag to clean the backside of the butterfly valve just below that air slot. Open it with the throttle lever. Once that is clean, start the engine and spray the rest of the can into the TB until it is empty.
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Old 07-15-2010, 06:34 PM   #3
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Thanks Jerry. Does it matter what brand of throttle body cleaner I get?
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Old 07-15-2010, 07:13 PM   #4

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No as long as its Throttle Body cleaner.
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