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Technical Q&A. HOW TO's, TSB's & Warranty Items Have a Problem? Technical Questions & Answers. HOW TO's & TSB's, Warranty Issues

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Old 10-15-2010, 07:45 AM   #1
blk03shkr
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Low Rough Idle

Had a couple problems lately with the Mach and wanted to get some peoples insight into what might be wrong. Car started idleing really low with AC on and would even stall out at red lights and such over the summer. When the AC was off the car seemed fine. I had installed the IAC restictor plate before the summer.

Recently the car started idleing rough and stalling without the AC on. I replaced the Alternator last week but no change. I removed the IAC restrictor plate and it still stalls. I just ordered a new IAC and im going to try that.

Any other things to check? Maybe a new battery or fuel issue?

The car is only idleing at like 400 rpms and surges slightly. I notice a drop in rpms when i press the brakes. Have to give it some throttle to start up also.

Thanks.
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Old 10-15-2010, 09:18 AM   #2
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Re: Low Rough Idle

fuel pressure regulator check it... little silver circle in the engine bay on the passenger side.. tap it sometimes help.. but its cheap and they always go on our cars..
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Old 10-15-2010, 11:10 AM   #3
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Re: Low Rough Idle

Our stock fuel systems are returnless, and have no FPR.


I would search for a vacuum leak. Vacuum is high at idle and that's when the car begins to stall. Also makes me think vacuum since you say it occurs when the brakes are being used.
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Old 10-15-2010, 11:52 AM   #4
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Re: Low Rough Idle

What are some areas to check for a vacuum leak first? How do i go about locating a vacuum leak?

The car will idle at around 400 rpms without pressing the break or any accessories on. If i press the break hard, it sometimes drops below that.
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Old 10-15-2010, 12:24 PM   #5
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Re: Low Rough Idle

A Haynes or Chilton manual will be your friend in these situations.
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Old 10-16-2010, 07:27 PM   #6
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Re: Low Rough Idle

Quote:
Originally Posted by Mach1Marauder View Post
Let us know what the IAC does.........remember....new gasket!
Replaced the IAC today. That was the problem, idles perfect now, with or without AC on. Got a new Battery too, still had the original one in there.
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Old 10-16-2010, 09:36 PM   #7
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Re: Low Rough Idle

Good deal
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Old 10-17-2010, 02:57 PM   #8
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Re: Low Rough Idle

Have another question, can a bad IAC make the car run rich causing exhaust blowback or backfire? Seems like the exhuast was backfiring more with the bad IAC during engine braking, i think it caused an exhaust leak.
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