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Old 07-08-2014, 04:15 PM   #1
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Default Low RPM and rough idle

HI all,

I had an issue several months ago where I blew out my UIM on my 92 bonnie.

I've replaced the complete UIM and replaced the gaskets on the LIM. since then, when I stat her up, she'* running at a very low RPM. The engine spins faster with the Starter than just the the engine.

On taking her for a test spin, I've noticed she runs much hotter. Just under the split between 200 and 280. Say 240 ish. I am running 100% water with some flush at the moment so that may be related, but I wanted to spell everything out.

Anybody run into this?

Thanks

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Old 07-08-2014, 04:19 PM   #2
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could be two sperate issues. have you cleaned the iac cone and port on the throttle body?
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Old 07-08-2014, 04:32 PM   #3
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No I have not. I'll check that out.
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Old 07-08-2014, 04:51 PM   #4
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Also, I forgot to mention that the fans are constantly running.

Not sure if that'* pertinent or not.
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Old 07-08-2014, 05:16 PM   #5
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i dont think it has anything to do with the idle. the fans may work properly once you change back to regular coolant and bleed the air out
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Old 07-08-2014, 10:03 PM   #6
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Thx JW,

BTW, I cleaned out the IAC, it ran fine for about 5 minutes while it was "ice" cold but as soon as I hit the first stop light (about 1 min), she started to shake again.

Any other ideas?

Thanks
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Old 07-09-2014, 07:42 AM   #7
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has the icm, wires, plugs, coils been done? have a fuel pressure gauge? cel on?
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Old 07-09-2014, 08:00 AM   #8
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Yes to plug and wires.

ICM?

What'* the test procedure for coil?

I'll check the pressure.

No CEL.
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Old 07-09-2014, 08:45 AM   #9
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OK, you come to a stop, and the idle drops......if it drops below 600 rpms, the idle will get rough....if you lightly step on the gas to raise the rpms above 600-700, does the roughness go away?

As JW said, putting the proper mix of coolant, a new therm, and properly bleeding the system may take care of the temp problem.....

Have you checked for codes, doing the flash procedure or using a code reader/scan tool?

When you had the top of the engine off, that was a good time to thoroughly clean the throttle plate and bore......

Could be an IAC or harness problem, especially if slightly raising rpms with gas pedal clears up the roughness.....

When car runs rough, shut off and disconnect the MAF sensor and see if car runs better......

Make sure air filter and box is clear.....

Check fuel pressure....last time fuel filter replaced?

If coolant got into the exhaust, it could have contaminated the O2 sensor....
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Old 07-09-2014, 12:03 PM   #10
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in addition to the things gus mentioned, i have had a couple times where the coil post started getting corroded, it will look dull instead of shiny. and it it will run kinda poor at idle or in fourth locked tq at low rpm like 40-50mph. if you dont put grease on the wires or plugs when replacing them it can run like that too
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