Idle high while rolling

HarryS · 08-12-2007, 08:35 AM

I have a 94, 5 speed, with a T4M0 computer. when slowing down and putting in the clutch the idle is held high, between 1200-1500, until the car comes to a complete stop. After being at a complete stop for 1-2 seconds the idle drops to normal, I don't remember the car doing this before, any ideas. Thanks.

USMC302 · 08-13-2007, 02:25 AM

Vacuum leak. IMO.

Jeff Chambers · 08-20-2007, 07:10 AM

When the car is moving, the PCM is in dashpot control mode, not idle control. If you've done modifications to the car, then you may need to have your tuner take a look at reducing the dashpot functions. If you haven't done any modifications recently, since the hanging idle started happening, then you'll need to look for sources of excess air such as vacuum leaks (USMC suggested), sticking IAC motor, excess EGR, excess air past the TB, etc.

08-12-2007, 08:35 AM	#1
HarryS Registered Member Join Date: Aug 2006 Posts: 5	Idle high while rolling I have a 94, 5 speed, with a T4M0 computer. when slowing down and putting in the clutch the idle is held high, between 1200-1500, until the car comes to a complete stop. After being at a complete stop for 1-2 seconds the idle drops to normal, I don't remember the car doing this before, any ideas. Thanks.

08-13-2007, 02:25 AM	#2
USMC302 Registered Member Join Date: Apr 2001 Location: Gallatin, Tn Posts: 1,326	Re: Idle high while rolling Vacuum leak. IMO. __________________

08-20-2007, 07:10 AM	#3
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	Re: Idle high while rolling When the car is moving, the PCM is in dashpot control mode, not idle control. If you've done modifications to the car, then you may need to have your tuner take a look at reducing the dashpot functions. If you haven't done any modifications recently, since the hanging idle started happening, then you'll need to look for sources of excess air such as vacuum leaks (USMC suggested), sticking IAC motor, excess EGR, excess air past the TB, etc. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"

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