98 F150 stalling.
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New User
Joined: Jan 2005
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98 F150 stalling.
I,m new to this, so I hope someone can help.
I drive a 98 F150 with a 4.2L V6 with auto tranny with 155,000+ miles. After a 40 min drive to work this morning the truck died when I came to a stop. Restarted and ran ok until the next time I stopped. This happened twice more before I parked at work. When parking, the truck died when I came to a stop. I restarted ok and put the truck in reverse and ran ok. When I put the truck in drive it died. I restarted and put the truck in low gear and it drove fine. Does anyone have any ideas? Thanks.
I drive a 98 F150 with a 4.2L V6 with auto tranny with 155,000+ miles. After a 40 min drive to work this morning the truck died when I came to a stop. Restarted and ran ok until the next time I stopped. This happened twice more before I parked at work. When parking, the truck died when I came to a stop. I restarted ok and put the truck in reverse and ran ok. When I put the truck in drive it died. I restarted and put the truck in low gear and it drove fine. Does anyone have any ideas? Thanks.
Lead Driver
Joined: Jul 2003
Posts: 7,404
Likes: 52
From: Wheatland, Mo
The IAC, (Idle Air Control valve), is real notorius for idling issues. A quick and easy test, is to remove it, clean and then try again. It should be located at the top back of the intake manifold. Remove the plastic cover of the intake manifold, (4 bolts), then locate the IAC. Takes 2 bolts and 1 wiring harness of 3 or 4 wires, to disconnect then just pull it out. Spray the inside with carb cleaner or brake cleaner untill you see all the black carbon is gone. Then dry THOUROUGHLY. Install it and try again.Now...if it runs a little better, it will only last for a short time, but now you know you need a new IAC. Replace it. Cleaning is for short time only. A new one is about $70.
Junior User
Joined: Nov 2004
Posts: 85
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From: North Gower/Ottawa
This morning at -30c my 98 4.6 F150 started fine with the block heater pluged in all night. The strange thing is it idled around 2400RPm and didn't slow down. After I shut it off and restarted it, 15 minutes later it ran at normal idle of 1000RPM. On other cold mornings when it started and it couldn't make up it's mind to either run at warm up speed or idle speed.
Would this be a sign of a faulty IAC.
Would this be a sign of a faulty IAC.
Junior User
Joined: Nov 2004
Posts: 85
Likes: 0
From: North Gower/Ottawa
(-22 fahrenheit) Reading the Haynes manual it says to check the voltages of the IAC and check to see if it shorted by reading the ohms and resistance of it. If there is no voltage from the PCM then its a dealer problem. If the ohns or resistance is out of wack then the ICM should be replaced. Does this make sence to anyone?
Junior User
Joined: Jun 2004
Posts: 51
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the iac is a duty cycle circuit.it is read by a percentage.this is contolled by the pcm. the first thing i do is take it off and clean it out, and replace the gasket. this will normally fix the problem. also being that cold, check for freezing or moisture in the throttle plates and in the iac. this is not common but i've seen it before. also make sure the throttle plate is clean as well.
