IDLE
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
Likes: 6
From: Vine Grove KY
IDLE
guys, I did a search on erratic idle and came up with all sorts of stuff on IAC, TPS, EGR and vacuum leaks and what not.
Is there a END ALL write up on here to properly diagnose erratic idle issues? Also, is there a procedure on the "re-learning" or resetting your computer by disconnecting the battery cables?
I am looking for a "how to" on how to check all the sensors for proper voltage and all that.
My truck dies when I come to a stop if the a/c is off. With a/c on it sometimes dies, but the idle jumps around when coming to a stop.
Is there a END ALL write up on here to properly diagnose erratic idle issues? Also, is there a procedure on the "re-learning" or resetting your computer by disconnecting the battery cables?
I am looking for a "how to" on how to check all the sensors for proper voltage and all that.
My truck dies when I come to a stop if the a/c is off. With a/c on it sometimes dies, but the idle jumps around when coming to a stop.
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
For the pinpoint tests, you want the Engine/Emissions Diagnosis shop manual (aka Powertrain/Emissions Diagnosis Manual)
Something like this:
1986 Engine/Emissions Diagnosis Manual Original
or this:
1986 Ford Engine Emissions Diagnosis Service Manual , Cars & Trucks | eBay
These books also cover diagnosis of user-reported problems.
In general, the diagnosis begins with checking for the obvious vacuum leaks and such, then pulling computer codes.
The Chiltons or Haynes (I forget which one) has a pretty decent ignition system diagnostic write-up.
You're most likely not really gonna find this information on the 'net for free... diagnosis can be a fairly involved procedure, procedures are different for different vehicles & different engines, and I don't know of anybody who wants to sit and type these books into a computer (copyright issues notwithstanding).
Could also get an AllData subscription, I think they're even running a special right now for FTE members...
AllData Gives FTE Members Discounts on Full Repair Info, Free Access to All TSBs and Recalls .: Articles
Something like this:
1986 Engine/Emissions Diagnosis Manual Original
or this:
1986 Ford Engine Emissions Diagnosis Service Manual , Cars & Trucks | eBay
These books also cover diagnosis of user-reported problems.
In general, the diagnosis begins with checking for the obvious vacuum leaks and such, then pulling computer codes.
The Chiltons or Haynes (I forget which one) has a pretty decent ignition system diagnostic write-up.
You're most likely not really gonna find this information on the 'net for free... diagnosis can be a fairly involved procedure, procedures are different for different vehicles & different engines, and I don't know of anybody who wants to sit and type these books into a computer (copyright issues notwithstanding).
Could also get an AllData subscription, I think they're even running a special right now for FTE members...
AllData Gives FTE Members Discounts on Full Repair Info, Free Access to All TSBs and Recalls .: Articles
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
A good site for general information about older Ford EFI components is:
Fuel Injection Technical Library
Fuel Injection Technical Library
Postmaster
Joined: Jan 2012
Posts: 3,462
Likes: 0
From: Richmond
86 302 in a truck would be CFI, correct?
Other than the links Chris posted, I haven't seen one. Online I mean. There was so much of a ditch it and run mentality with the CFI. I believe both because it replaced the carburetor that's god like in many people's opinions. And Was quickly replace buy improvements in SEFI. Online it's a bit like trying to find information on the smog systems. Wading through all of the "just tear it out we don't need no gubment man tellin us how to not get 9mpg !!11!" crap.
Chris, are we allowed to reference other forums? If so I know of an archive on CFI. I haven't read a lot of it, but it's larger than most at least.
In general for idle:
Vacuum
Electronic tolerances.
Fuel
Timing
Curse
Sweat
Cry
Cruse and so on.
Other than the links Chris posted, I haven't seen one. Online I mean. There was so much of a ditch it and run mentality with the CFI. I believe both because it replaced the carburetor that's god like in many people's opinions. And Was quickly replace buy improvements in SEFI. Online it's a bit like trying to find information on the smog systems. Wading through all of the "just tear it out we don't need no gubment man tellin us how to not get 9mpg !!11!" crap.
Chris, are we allowed to reference other forums? If so I know of an archive on CFI. I haven't read a lot of it, but it's larger than most at least.
In general for idle:
Vacuum
Electronic tolerances.
Fuel
Timing
Curse
Sweat
Cry
Cruse and so on.
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
Absolutely!
There are links in the Sticky to good information on FSB and other forums & sites.
BTW I don't think the trucks ever did CFI, they were either Feedback Carb or EFI.
Ya know, I have one of those powertrain diagnosis books for my bro's 1993 Taurus. In its defense, it covers all Ford cars and probably even light trucks.
But, it's quite literally at least 8" thick!
But the information contained it just amazes me. I was so impressed with it, I bought the 1986 version for my DD Tempo.
BTW here is some diagnosis information from therangerstation.com:
Ford Ranger/Bronco II TFI Ignition Diagnostics
Ford Ranger/Bronco II EEC-IV Testing <-- Basically, instructions on pulling codes, similar to oldfuelinjection.com's help on this:
Fuel Injection Technical Library » How To Run a Self-Test
There are links in the Sticky to good information on FSB and other forums & sites.
BTW I don't think the trucks ever did CFI, they were either Feedback Carb or EFI.
Ya know, I have one of those powertrain diagnosis books for my bro's 1993 Taurus. In its defense, it covers all Ford cars and probably even light trucks.
But, it's quite literally at least 8" thick!
But the information contained it just amazes me. I was so impressed with it, I bought the 1986 version for my DD Tempo.
BTW here is some diagnosis information from therangerstation.com:
Ford Ranger/Bronco II TFI Ignition Diagnostics
Ford Ranger/Bronco II EEC-IV Testing <-- Basically, instructions on pulling codes, similar to oldfuelinjection.com's help on this:
Fuel Injection Technical Library » How To Run a Self-Test
Postmaster
Joined: Jan 2012
Posts: 3,462
Likes: 0
From: Richmond
My mistake. I thought the 302 echoed what the coupes and sedans did. CFI, then finally SEFI in 87. Thought 86 and a truck I bet you're right. But either way, here's that CFI library I was talking about.
CFI/Electrical Archive
CFI/Electrical Archive
Thread Starter
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
Likes: 6
From: Vine Grove KY
Guys, thanks for all the links. I didn't have this problem until I put in a new battery and got my a/c working. Maybe when I put the new battery in I turned the a/c on at the same time. By the sound of it, that may be a bad idea for the computer to learn how to idle again. I have the cables off right now. I am going to go put them back on in a little while and let it idle for two minutes, and then drive it for two minutes a/c off. Then we will see how it does.
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Postmaster
Joined: Jan 2012
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From: Richmond
Not familiar with the setup, but if the A/C is supposed to have a sensor, lever, whatever to advance the idle when it's turned on...Does it idle better if you put your foot down maybe even 1-200rpm?
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Thread Starter
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
Likes: 6
From: Vine Grove KY
I don't have a tach. When i switch on the A/C it usually idles faster. If I am coming to a stop sometimes it wants to die with the a/c off. With the a/c on coming to a stop is erratic. It may idle just fine coming to a stop, but other times it surges the idle and I have to apply more brake to stop. Its like the IAC can't find a happy place.
Postmaster
Joined: Jan 2012
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From: Richmond
They commonly fail on a couple cars I've owned. If you replaced it, could still be suspect out of the box. If you know what values you're supposed to have at what rpm, I've driven with a volt meter visible from the driver's seat to check this before.
Or maybe it's the good old unmetered air gremlins.
Or maybe it's the good old unmetered air gremlins.
Thread Starter
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
Likes: 6
From: Vine Grove KY
Okay. Just hooked up the bettery again. Let it idle. It fired right up, kinda sputtered, then came to life. I let it idle for a couple minutes. Switched on the a/c and it idled up. Switched off the a/c and it darn near died. I unhooked the IAC and it wouldn't start.
Shouldn't the truck idle just fine without the IAC hooked up? So I assume that the idle screw has been messed with. I kept turning the screw in until it would fire up. Then I hooked up the IAC and it surged a bit then idled down and erratically for a minute.
Took it for a spin and it seems a little better now. It didn't die when I came to a stop, and it didn't idle up and down when coming to a stop either.
Shouldn't the truck idle just fine without the IAC hooked up? So I assume that the idle screw has been messed with. I kept turning the screw in until it would fire up. Then I hooked up the IAC and it surged a bit then idled down and erratically for a minute.
Took it for a spin and it seems a little better now. It didn't die when I came to a stop, and it didn't idle up and down when coming to a stop either.
Thread Starter
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
Likes: 6
From: Vine Grove KY
How do I hook up the voltmeter to the IAC? What voltage should I get at idle, and at certain rpm's?
Postmaster
Joined: Jan 2012
Posts: 3,462
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From: Richmond
Haven't dealt with Ford ignition systems before, but many will not run without the IAC. A lot of systems close the throttle completely, and use the idle valve to supply the idle air. If unpowered is default close, then it would die with no idle air.
Have you replaced, or at least cleaned it? Sounds like you're off with air/fuel mixture. The AC pickup probably provides just enough speed to keep it running. Try putting the truck in N and a slightly revving with the A/C off as you come to stop, see what happens.
If you haven't clean the IAC then get some throttle cleaner and 2 paper towels. spray until you can hear the element moving.
Is the IAC controlled by a 2 or 3 wire harness? I had two wires that measured the power feedback from the internals of the IAC. Connected test leads to them and ran the wires into the cab.
Doe the IAC have two short, molded, rubber hoses connecting it to both sides of the throttle body? Take those off and manipulate them to check for cracks. Can't always be seen on the car.
Have you replaced, or at least cleaned it? Sounds like you're off with air/fuel mixture. The AC pickup probably provides just enough speed to keep it running. Try putting the truck in N and a slightly revving with the A/C off as you come to stop, see what happens.
If you haven't clean the IAC then get some throttle cleaner and 2 paper towels. spray until you can hear the element moving.
Is the IAC controlled by a 2 or 3 wire harness? I had two wires that measured the power feedback from the internals of the IAC. Connected test leads to them and ran the wires into the cab.
Doe the IAC have two short, molded, rubber hoses connecting it to both sides of the throttle body? Take those off and manipulate them to check for cracks. Can't always be seen on the car.