erractic idle at start up
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Senior User
Joined: Mar 2009
Posts: 134
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erractic idle at start up
The truck-1996 f250, 460, e4od, 4x4. its a mass air CA truck.
Here's the issue, after starting the truck idles around 1200 rpm, every so often it will dip down to around 500 rpm like it wants to die, but then goes back up to 1100 rpm or so. it does this a few times before it smooths out and idles normally. I was thinking it might be the iac but not sure since it is in open loop when it happens. I checked the computer and got no codes present. Any ideas where to start looking?
Here's the issue, after starting the truck idles around 1200 rpm, every so often it will dip down to around 500 rpm like it wants to die, but then goes back up to 1100 rpm or so. it does this a few times before it smooths out and idles normally. I was thinking it might be the iac but not sure since it is in open loop when it happens. I checked the computer and got no codes present. Any ideas where to start looking?
More Turbo
Joined: Dec 2002
Posts: 705
Likes: 2
From: Halifax, NS
I'm dealing with a similar thing with my truck.
Here is the thread: https://www.ford-trucks.com/forums/1...t-startup.html
For mine, I think it has to do with the MCU/EECIV deciding it has to re-learn the idle every time I start my truck for some reason.
This only started happening after a storm with lots of wind-driven rain. Not sure if it's related or not.
Tell me this, do you get the light flashing when this happens ??
I have tried pulling/clearing codes, doesn't seem to matter.
My next step is to try a longer battery disconnect, (30 mins) as well as the procedure in this thread:
http://www.allfordmustangs.com/forum...procedure.html
I am hoping this will solve the issue for me. Hope to try it in a few days time.
Here is the thread: https://www.ford-trucks.com/forums/1...t-startup.html
For mine, I think it has to do with the MCU/EECIV deciding it has to re-learn the idle every time I start my truck for some reason.
This only started happening after a storm with lots of wind-driven rain. Not sure if it's related or not.
Tell me this, do you get the light flashing when this happens ??
I have tried pulling/clearing codes, doesn't seem to matter.
My next step is to try a longer battery disconnect, (30 mins) as well as the procedure in this thread:
http://www.allfordmustangs.com/forum...procedure.html
I am hoping this will solve the issue for me. Hope to try it in a few days time.
Thread Starter
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Senior User
Joined: Mar 2009
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no i dont get any lights flashing. i only started noticing it when it's cold outside. but the funny thing is i was out at Pismo beach last week and it was down to mid 30's and i didnt notice it at all. kinda weird.
Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
I would lean more towards a gummed up IAC solenoid for your issue. It can be removed for cleaning. Although many have found that to be a short term fix. At least if it works for awhile, you know you are on the right track.
Thread Starter
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Senior User
Joined: Mar 2009
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wasn't sure if it could be the iac valve or soenoid since it does it in open loop ode but i was kinda thinking that could be the culprit anyway. gona check that out this weekend when the suns out. wil let you guys know.
Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
Do not gloss over the fact idle RPM is a closed loop operation. The PCM is looking at several inputs to determine the idle RPM. A sticking/fouled IAC, vacuum leaks, faulty TPS/ECT/ACT or other sensors will affect that operation.
I reference this quite often from Ryan: Ford Fuel Injection » Strategies
I reference this quite often from Ryan: Ford Fuel Injection » Strategies
