4.9L Idle Issues
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4.9L Idle Issues
I have a 1992 F150 with the 4.9L and the M5OD-R2 transmission. I recently hauled around 2,500 lbs in the bed for a philanthropy event I was running ( yes yes I know that was too much) I never went above2nd and it was less than a mile. Anyways now when I shift gears the engine goes up to 2,000 rpm then revs down to 1,100 rpm. 1,100 rpm is where it has always idled at.
I am thinking it is the throttle body or a throttle cable but what do you guys think. If it is the throttle body is it good enough to clean it or should I just buy a new one?
It could be a vacuum problem but I could see no cracking or missing pieces but then again cruise control doesn't work.
Let me know what yall think.
I am thinking it is the throttle body or a throttle cable but what do you guys think. If it is the throttle body is it good enough to clean it or should I just buy a new one?
It could be a vacuum problem but I could see no cracking or missing pieces but then again cruise control doesn't work.
Let me know what yall think.
Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
I have a 1992 F150 with the 4.9L and the M5OD-R2 transmission. I recently hauled around 2,500 lbs in the bed for a philanthropy event I was running ( yes yes I know that was too much) I never went above2nd and it was less than a mile. Anyways now when I shift gears the engine goes up to 2,000 rpm then revs down to 1,100 rpm. 1,100 rpm is where it has always idled at.
I am thinking it is the throttle body or a throttle cable but what do you guys think. If it is the throttle body is it good enough to clean it or should I just buy a new one?
It could be a vacuum problem but I could see no cracking or missing pieces but then again cruise control doesn't work.
Let me know what yall think.
I am thinking it is the throttle body or a throttle cable but what do you guys think. If it is the throttle body is it good enough to clean it or should I just buy a new one?
It could be a vacuum problem but I could see no cracking or missing pieces but then again cruise control doesn't work.
Let me know what yall think.
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Junior User
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I checked for codes and had no codes with the engine running and a voltage code for the egr with the key on engine off.
I unplugged the IAC and it idles around 850 rpm. If I replaced it would it stay around 850 and is it fine to drive with it unplugged until I get a new one?
I unplugged the IAC and it idles around 850 rpm. If I replaced it would it stay around 850 and is it fine to drive with it unplugged until I get a new one?
Elder User
Joined: Sep 2018
Posts: 735
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From: NC
I checked for codes and had no codes with the engine running and a voltage code for the egr with the key on engine off.
I unplugged the IAC and it idles around 850 rpm. If I replaced it would it stay around 850 and is it fine to drive with it unplugged until I get a new one?
I unplugged the IAC and it idles around 850 rpm. If I replaced it would it stay around 850 and is it fine to drive with it unplugged until I get a new one?
It's not exact but will give you an idea how to do it:
https://www.ford-trucks.com/how-tos/...c-valve-430372
Lead Driver
Joined: Oct 2016
Posts: 6,185
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From: Houston/Sugar Land
check fuse # 13 under dash for cruise.
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Junior User
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Take your IAC off and clean it. It may be just dirty. If no change then we can go from there.
It's not exact but will give you an idea how to do it:
https://www.ford-trucks.com/how-tos/...c-valve-430372
It's not exact but will give you an idea how to do it:
https://www.ford-trucks.com/how-tos/...c-valve-430372
I think the high idle could just be worn throttle body, I saw in a previous thread that fixed his idle.
Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
Check your brake on off switch at the pedal. If good check brake pressure switch. .... Remove throttle body and look for light showing around closed butterfly valves. Usually the issue is a bad throttle body gasket. Replace yours regardless. Dry. Replace IAC gasket if it was compromised,
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Junior User
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Check your brake on off switch at the pedal. If good check brake pressure switch. .... Remove throttle body and look for light showing around closed butterfly valves. Usually the issue is a bad throttle body gasket. Replace yours regardless. Dry. Replace IAC gasket if it was compromised,
Lead Driver
Joined: Oct 2016
Posts: 6,185
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From: Houston/Sugar Land
I would buy the gaskets but not put them on yet. As Zombie suggested cleaning the IAC may have caused the magic. After a cleaning sometimes the problem will reappear and you will need to replace the IAC if it does. Then replace both gaskets. In the meantime leave it as is.
Elder User
Joined: Sep 2018
Posts: 735
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From: NC
I agree with Sandy, if it seems to have been straightened out, run it and make sure the problem doesn't come back.
I replaced my throttle body gasket about a year ago but that is because I removed the throttle body so i could do some work and look inside the chamber. It is like 2 bux,
I replaced my IAC not because mine was bad but it was original as were the other parts i changed out. All of them still worked but they are getting some age to them and they are kept as spares. IAC gasket is about 2 bux. Heck I have one I can mail ya if you need it.
BTW @sandymane My power steering pump is the quietest I have ever heard it. Did the turkey baster and MMO fluid change one more time and then refilled it with type F. A week later it is as quiet as ever and fluid is nice and clear.
I replaced my throttle body gasket about a year ago but that is because I removed the throttle body so i could do some work and look inside the chamber. It is like 2 bux,
I replaced my IAC not because mine was bad but it was original as were the other parts i changed out. All of them still worked but they are getting some age to them and they are kept as spares. IAC gasket is about 2 bux. Heck I have one I can mail ya if you need it.
BTW @sandymane My power steering pump is the quietest I have ever heard it. Did the turkey baster and MMO fluid change one more time and then refilled it with type F. A week later it is as quiet as ever and fluid is nice and clear.