irratic idle
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5th Wheeling
Joined: Jan 2003
Posts: 47
Likes: 0
From: Oregon Coast
irratic idle
My 1989 F350 EFI 460 5spd is not running well. There have been no code showing up so I was using my Haynes manual. It states that key on voltage at the IAC should be approximately 10.5 volts. I get 12 volts when I checked it and I am not sure what this means.
Thanks in advance
Matt
Thanks in advance
Matt
Lead Driver
Joined: Feb 2003
Posts: 8,140
Likes: 4
From: Oak Harbor, OH
irratic idle
unplug the IAC and see if it runs smoother..... it will only idle as the IAC controls the idle return. it will stall if you rev it, if you unplug the IAC and it quits replace the IAC... I would check the TPS first tho.
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
irratic idle
Try cleaning the IAC and the throttle body. Also check for vacuum leaks particularly at the back of the intake "elbow" that the throttle body attaches to. There is a vacuum plug there that falls off sometimes. Also check the vacuum "tree" at the front of the intake for missing plugs.
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5th Wheeling
Joined: Jan 2003
Posts: 47
Likes: 0
From: Oregon Coast
irratic idle
Thanks for the replys. I have checked the TPS, IAC and have looked and looked for a vacuume leak and have found none. The intake is clean which is why I am down to checking voltages and wondering if the reading of 12 volts instead of 10.5 is the root of the problem. Anything that Iam missing
Matt
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
irratic idle
You should have battery voltage at the red ( I think) wire to the IAC. The PCM controls the ground side of the IAC.
When you checked for vacuum leaks did you just look for them or spray the intake down with some carb cleaner spray or something?
When you checked for vacuum leaks did you just look for them or spray the intake down with some carb cleaner spray or something?
Lead Driver
Joined: Feb 2003
Posts: 8,140
Likes: 4
From: Oak Harbor, OH
irratic idle
when you sprayed did the motor surge or act like it was going to stall? smell the exhaust, if it smells sweet you may have a failing head gasket
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5th Wheeling
Joined: Jan 2003
Posts: 47
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From: Oregon Coast
irratic idle
when I sprayed the intake with carb cleaner it did not change the idle and the exhaust does not have a sweet smell just black from running too rich.
Matt
Matt
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Thread Starter
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5th Wheeling
Joined: Jan 2003
Posts: 47
Likes: 0
From: Oregon Coast
irratic idle
This has been a tough problem for me. The truck will not run well at any engine speed but this has gotten progressivly worse. It runs very rich (black smoke) but only sometimes. It will be idling fine and then it seem to load up and starts smoking. I had it running great for about a week but one evening when I started it up it ran really badly. Would not idle on its own and surging below about 2500 rpm. Both temp sensors have been replaced along with the TPS and IAC. I have even tried another MAP sensor and nothing has helped. A leak down test was fine also. Ideas?
Matt
Matt
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
irratic idle
Have you checked your fuel pressure? I'm wondering if your regulator is shot. Tried flushing your injectors? I've seen injectors act up intermittantly. It seems that there was some junk floating around in the fuel rails and causing problems sometimes.
O2 sensor bad maybe? Usually they wont be intermittant but you never know.
O2 sensor bad maybe? Usually they wont be intermittant but you never know.
Senior User
Joined: Sep 2001
Posts: 291
Likes: 1
From: Central Texas
irratic idle
have had experience with sensors bad and no codes. I dont remember what the correct voltage reading should be. There's several posts on this forum about oxygen sensor problems.
Last edited by dbrown13; Feb 18, 2003 at 10:18 AM.