Idle Problem

Bob99GTConv · 12-06-2004, 08:42 AM

When I run the AC or heater my idle goes up and down from 500 to 1500rpm a few times then eventually dies. Now, the other day I was driving along without the AC and it just died on me! I have replaced the Idle Air Control Valve, the TPS, and the MAF is clean. Any ideas? All this started before I ever made any upgrades, and it's still going on.

xxxBlakexxx · 12-08-2004, 08:09 PM

Well, you have checked all the usual suspects. Sous to me like your base idle is set too low and the idle is hunting. The problem will get worse with the AC running.

Here is how to fix it:

1 - Start the car.

2 - With the motor running, unplug the wire harness to the IAC. If the car dies, you have found your problem.

3 - When you unplug the harness, the car should almost die, but not stop running. If the idle is unaffected by removing the harness, then the idle is set too high.

4 - Adjust the idle set screw on the TB until the car just barely runs with the harness removed.

5 - The SES will come on...no worries. Disconnect the battery to reset the idle speed fuel curves and reset the light. Reconnect and you owe me a favor! If this does not work, then sell it.

blue00gt · 12-09-2004, 03:36 PM

If your AC is low on refrigerant it can contribute to the idle going up and down too, but it wouldn't cause the other things you are seeing.

paver one · 12-15-2004, 01:38 PM

IAC's can be cleaned by removing and spraying with carb cleaner. That sometimes helps to stabilize the idle..........

Red Mustang Gt 46 · 12-31-2004, 08:02 AM

Bob, this is one of those "usnusual" problems...but it sounds to me like a bad solenoid/sensor somewhere. I would OBD2 scan your EEC and then work it from there, heres some of the codes you may find:

http://www.allfordmustangs.com/Detailed/445.shtml

There are too many things that could cause your problem...

12-06-2004, 08:42 AM	#1
Bob99GTConv Registered Member Join Date: Dec 2004 Posts: 5	Idle Problem When I run the AC or heater my idle goes up and down from 500 to 1500rpm a few times then eventually dies. Now, the other day I was driving along without the AC and it just died on me! I have replaced the Idle Air Control Valve, the TPS, and the MAF is clean. Any ideas? All this started before I ever made any upgrades, and it's still going on. __________________ 1999 GT Conv - 5spd 3.73's Accufab 75mm throttle body/plenum Cold Air Intake 40 series Flowmasters Nitto Drag Radials

12-08-2004, 08:09 PM	#2
xxxBlakexxx Registered Member Join Date: Sep 2003 Location: Mountaintop, PA Posts: 634	Re: Idle Problem Well, you have checked all the usual suspects. Sous to me like your base idle is set too low and the idle is hunting. The problem will get worse with the AC running. Here is how to fix it: 1 - Start the car. 2 - With the motor running, unplug the wire harness to the IAC. If the car dies, you have found your problem. 3 - When you unplug the harness, the car should almost die, but not stop running. If the idle is unaffected by removing the harness, then the idle is set too high. 4 - Adjust the idle set screw on the TB until the car just barely runs with the harness removed. 5 - The SES will come on...no worries. Disconnect the battery to reset the idle speed fuel curves and reset the light. Reconnect and you owe me a favor! If this does not work, then sell it. __________________ "Children should not get cancer, but they do!" Help a child with cancer at www.homeoftheirown.org My Stang: 2000 Mustang GT Vert - Steeda Tri-Ax Shifter; C&L Plenum; BBK 75 mm TB; Steeda Strut Tower Supports; Black "Deep Dish" Bullet Wheels; FRPP 4.10's; Steeda Subframes; SLP Catback & SLP Catted X-Pipe; SCT 4 Position Chip with 3 custom tunes; Steeda CAI; Venom-1000 Nitrous; Roush Stage 3 Body Kit; Bullet Suspension Package (on the way)

12-09-2004, 03:36 PM	#3
blue00gt Mustang Addict Join Date: Jan 2001 Location: McKinney, TX Posts: 1,294	Re: Idle Problem If your AC is low on refrigerant it can contribute to the idle going up and down too, but it wouldn't cause the other things you are seeing. __________________ Strike down the unroadworthy! 2000 GT Atl. Blue: '03 Cobra motor - 465rwhp/473rwtq, T-56 6-speed, full MM TA/PH & tubular K-member suspension, Saleen body, 17" Torq-Thrust II's, M/T ET Street radials, and lots more '94 Rio Red Cobra: All the bolt-ons, 3.73s

12-15-2004, 01:38 PM	#4
paver one Registered Member Join Date: Jan 2000 Location: Ogden Utah Posts: 58	Re: Idle Problem IAC's can be cleaned by removing and spraying with carb cleaner. That sometimes helps to stabilize the idle.......... __________________ 1999 F-350 CC Dually PStroke,1996 SALEEN s281SC vert #380 & 2004 F-150 FX4 Crew Cab

12-31-2004, 08:02 AM	#5
Red Mustang Gt 46 13.3 @ 103 Join Date: May 2001 Location: Maryland Posts: 253	Re: Idle Problem Bob, this is one of those "usnusual" problems...but it sounds to me like a bad solenoid/sensor somewhere. I would OBD2 scan your EEC and then work it from there, heres some of the codes you may find: http://www.allfordmustangs.com/Detailed/445.shtml There are too many things that could cause your problem... __________________ Equipment by: Steeda C&L COMP CAMS FRPP MSD Bassani Magnaflow MAC

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