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Engine RPMs flutter and do not stay constant.
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Deception
New User
Sep 12, 2009, 8:28 AM
Post #1 of 3
(5977 views)
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Engine RPMs flutter and do not stay constant.
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I have a 93 Ford Probe GT 2.5L Manual transmission, just over 100,000Miles. It was an aftermarket Air Ram, 2 month old racing plugs and wires.
I had a problem last year where my engine would flutter the rpms from 700-900 rpms when idling and then sometimes it would surge up to over 3000RPMS. If i tried to give it gas when it was doing this when driving it would jerk the car.
Took it to my Mechanic and they had the problem happen to them but couldn't get any codes out of it and suggested i replace the Throttle position sensor, and/or mass airflow sensor.
I changed them both a few times and nothing worked, but then i finally got a code out of the car, and it told me my Engine Coolant thermostat and fan thermostat were causing problems.
I finally changed the sensors 2 days ago, and i haven't noticed the extreme surging yet (crossing fingers) but i have noticed a slightly smaller problem.
When i turn my cold on from cold, just let it idle it runs perfectly smooth, not a flutter or anything and idles perfectly at 600RPM (aprox.) and will stay there for as long as it sits.
Though it will start to flutter when i apply the gas peddle, when i let it go back to idle, it now sits around 750rpm and flutters up and down. Any idea why this is happen?
Also i have 7 controls on my vents. Max A/C, Norm A/C, Vent, Off, Floor, Mix, Windshield Defrost.
When the controls are on Vent, Off, or floor the rpm stays around 600, but also noticed it drop to sometimes 350 fluttering, when i turn it to windshield, a hear a hiss for about 2 seconds and the rpms shoot up to just above 1000, and then flutter around 750-900, same on mix, and the A/Cs yet i hear no his.
Any help on why my rpms wont stay steady would be greatly appreciated. I have fought this for over a year and getting better but still this annoying problem
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Sidom
Veteran
/ Moderator
Sep 12, 2009, 11:58 AM
Post #2 of 3
(5972 views)
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Re: Engine RPMs flutter and do not stay constant.
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but then i finally got a code out of the car, and it told me my Engine Coolant thermostat and fan thermostat were causing problems. Just to keep things straight. Codes don't tell a tech what is wrong, they let you what system is being affected and there is a lot of things that can affect a systems. . . .. There are a few things that can cause this. Vacuum leaks being one of them. It sounds like you have one in HVAC system when switching modes. The quickest thing would be to find the vacuum line under the hood by the firewall for the HVAC controls and disconnect & plug the line and see if that makes a difference (The system should default to defrost when you do this). Check all the other vacuum lines to make sure there are no breaks or splits. Clean out the throttle body & IAC motor (Idle air). After that it gets a little tougher to diagnose, to make matters a little worse, all that aftermarket stuff, while it may be cool, can have an affect on the factory systems in a ways you wouldn't realize and makes the diag even tougher.........
(This post was edited by Sidom on Sep 12, 2009, 11:58 AM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 13, 2009, 5:50 PM
Post #3 of 3
(5943 views)
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Re: Engine RPMs flutter and do not stay constant.
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To add to already said: Put it back to OE. Guessing with aftermarket stuff just confuses issues IMO,
T
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