97 TJ won't start without me pumping the accelerator - Jeep Wrangler Forum
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Old 11-10-2015, 08:02 PM
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97 TJ won't start without me pumping the accelerator

A new issue has come up....I now have to pump or hold down the gas pedal to get the TJ to start and stay at an idle. After about 10 seconds of keeping it running it will stay running on its own. This happens everytime I start it, even right after shutting it off.

Any clues?

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Old 11-10-2015, 08:07 PM   #2
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Probably a stuck/dirty IAC (idle air controller). The IAC is what is what provides all the air to the engine when you're not stepping down on the gas pedal to open the main butterfly valve plate. So when it's dirty and doesn't open enough, the engine starves for air until you step down on the gas pedal a little to open the main butterfly valve plate.

You can remove it with a T-20 or T-25 torx driver and clean it with some aerosol throttle body cleaner and a rag or soft tooth brush. Be gentle with the IAC's plunger and be sure to clean the hole in the throttle body that the IAC's plunger fits into too.
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Old 11-10-2015, 08:11 PM
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I do have a slow battery drain issue that I have been trying to find. Will a weak battery cause this?
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Old 11-10-2015, 08:15 PM   #4
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....I now have to pump or hold down the gas pedal to get the TJ to start and stay at an idle.
On a carbureted engine, pumping the accelerator pedal activated the acceleration pump. On a MPI engine, I can't see that it does anything at all.
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Old 11-10-2015, 08:21 PM   #5
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Let's in more air so if way over rich say from a leaky injector might just let it start
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Old 11-10-2015, 08:26 PM   #6
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I do have a slow battery drain issue that I have been trying to find. Will a weak battery cause this?
A bad battery can definitely cause idle issues but only if the battery is so weak your engine needs a jump start battery to get it started. If you can start your engine normally your idle issue is more likely related to the IAC.
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Old 11-10-2015, 09:07 PM   #7
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A bad iac should not fix itself after a brief run as if not open enough allow enough air to keep idle alive would still be a problem with throttle body closed

An over rich on the other hand would improve both as residual leaked fuel is consumed and as it goes closed loop and can correct with fuel trim

I would pull rail leaving injectors attached and see if any injectors leak

I would also hook up a good obd2 reader and look at live data fuel trim

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