Low idle question
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Joined: Dec 2002
Posts: 1
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Low idle question
88 bronco,351.
It will not idle above 600 rpm.Starts ok seems to run fine,maybe a little off power but nothing too noticeable.Even when cold the idle stays around 900-1000 and then drops down to ~550.
I don't have a manual yet.
Is this a common problem?
Should I be looking at a specific sensor?
Any help would be appreciated.
Thanks
It will not idle above 600 rpm.Starts ok seems to run fine,maybe a little off power but nothing too noticeable.Even when cold the idle stays around 900-1000 and then drops down to ~550.
I don't have a manual yet.
Is this a common problem?
Should I be looking at a specific sensor?
Any help would be appreciated.
Thanks
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Low idle question
Not sure that there is a lot of problem there. My 92 idles at about 650 in gear warm. I'd check for dirty throttle body and associated parts before replacing anything. Could just be dirty intake and TB. There have been several posts regarding cleaning techniques. Mine idles high for a few minutes when cold but drops back after a bit. Doesn't seem to have any adverse effects.
Senior User
Joined: Jun 2002
Posts: 241
Likes: 0
From: Colorado Springs, CO
Low idle question
My 88 351 does the same. And it surges. I'm in the process of replacing the TPS, but may do the Idle air bypass valve. I think thats the same thing as the IAC. Would the IAC cause surging?
Brian
Brian
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
Low idle question
The IAC is also call the ByPass Air Idle Speed Control servo (BPA-ISC), and it's totally inactive whenever the TPS is NOT sending the idle-position signal to the computer. So the IAC can't cause surging except at idle, and that's not even common.
For surging, I'd look at vacuum leaks, ignition, and fuel pressure.
For surging, I'd look at vacuum leaks, ignition, and fuel pressure.
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
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Senior User
Joined: Jun 2002
Posts: 241
Likes: 0
From: Colorado Springs, CO
Low idle question
Thanks for the help Steve! I replaced the TPS and the IAC and now it runs like a champ. No more surging! I've had this problem for 6 months and I'm glad I finally figured it out.
Brian
1988 351 EFI
Brian
1988 351 EFI
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