high idle problem
#16
07-24-2010, 12:38 PM
I hate to ask this, but are you Certain the A/C charge is up to snuff????
If it's low, or too high, the low or high pressure switch will turn the compressor off, but the computer will think it's on, because the in cabin HVAC switch is still in the A/C, or Defrost position.
So the computer thinks the compressor load is still on line & it has to go at throttle up!!!
If it's low, or too high, the low or high pressure switch will turn the compressor off, but the computer will think it's on, because the in cabin HVAC switch is still in the A/C, or Defrost position.
So the computer thinks the compressor load is still on line & it has to go at throttle up!!!
#17
07-24-2010, 09:20 PM
#18
07-25-2010, 12:50 PM
I hate to ask this, but are you Certain the A/C charge is up to snuff????
If it's low, or too high, the low or high pressure switch will turn the compressor off, but the computer will think it's on, because the in cabin HVAC switch is still in the A/C, or Defrost position.
So the computer thinks the compressor load is still on line & it has to go at throttle up!!!
If it's low, or too high, the low or high pressure switch will turn the compressor off, but the computer will think it's on, because the in cabin HVAC switch is still in the A/C, or Defrost position.
So the computer thinks the compressor load is still on line & it has to go at throttle up!!!
#19
07-25-2010, 12:56 PM
i am very stubborn when it comes to taking my vehicle to a mechanic, but at this point it may be my only option due to them having an "active" scanner.
#20
07-25-2010, 01:43 PM
The A/C clutch cycling pressure switch is normally open, at or below 24.5 psi because of low pressure & it's closed at or above 43.5 psi & sends operating votage to the high pressure cutoff switch.
The A/C high pressure side cutoff switch closes at 230-290 psi to let the compressor operate & opens at 460-490 psi to disengage the clutch & turn the A/C compressor off because of over pressure.
SO, then when you call for the A/C compressor to run, is the compressor clutch closing & causing the compressor to rotate/come on & is it staying on????
If the compressor isn't rotating, you likely have a clutch problem & the computer thinks the compressor load is on line & it should have the IAC go at throttle up, to compensate, thus an rpm surge.
If the clutch closes & turns the compressor, but it stops right away, maybe the system pressure is off, or one of the pressure switches is acting out, or there is a wiring problem.
If you come to think it's a pressure switch problem, give it a thump & see it it'll wake up.
If all that comes to naught, then we'll have to move on to the next step.
#21
07-29-2010, 03:42 PM
but unfortunately that is not the problem. the clutch kicks on and grabs like normal, and it stays on.
additional info that makes it even more fun.
when sitting in the driveway, if i turn the a/c on the problem does not happen until i get going and cycle the throttle a few times, then wham! idle goes through the roof and stays there. it used to go away as soon as i turn the a/c off. but now it will not go away unless i pull over, shut the car off, then start it back up. but if i never turn the a/c on, the problem never happens. so that completely rules out the possibility of the clutch slipping, even if it was happening only while driving and when i would be less able to notice.
gotta love how every year that goes by auto makers priority is to make it as painful as possible to work on a car yourself, and in addition to that, planned obsolecense, nothing is built to last anymore either.
i just dont ever seem to have problems with my dirtbike or old truck. but my computerized streetbike and computerized new truck are a constant nuissance.
#22
07-29-2010, 03:53 PM
#23
09-16-2010, 05:49 PM
special thanks to paw paw for all his help... but the problem is nothing what you wouldve expected. you'll never guess! it was the battery.
only and i mean only when i used to turn the a/c on, or any function that required the compressor to be on.... the idle would go through the roof!
this is such a rare problem that nobody has ever heard of and i would like to pass the knowledge along so i can save anybody else from any headaches. please add it to the tech section or wherever need be cause its a doozey!
the battery worked just fine the way it was, i've owned the truck for like 9 months now and its always started just fine, alternator did go out at one point and i replaced it but. so what really prompted me to replace the battery is that here and there it would crank the engine weak. and i looked at the age of the battery. it was old as hell! so i figured its preventative maintenance and bought a new battery thats the same 610 cca.
and it was a magic pill. and no there was nothing wrong with any of the battery terminals or cables and i didnt possibly wiggle anything that wouldve been that magic pill. the battery was the fix. and now i see why......
the alt and batt work together to power the vehicle. a/c compressor clutch requires lots of juice, and so does the fan for the cabin, especially if its hot as hell out and you turn the fan up. the battery and alternator team could not handle the load, so the computer went into some sort of mode that would crank the idle up through the roof. and then it was getting to the point where even if you turn the a/c off. the computer was still in that wierd mode. it was still telling the iac valve to go haywire. so i would then have to shut if off, restart it, and not touch the a/c. it now works like a champ and decellarates nicely too, and doesnt act like a wacko cruise control of death. (its a stick, if it was auto it probly wouldnt of been driveable.
so everybody whether you have a problem or not, and your battery is old, replace it anyway. spend the 80 bucks. because its a vital thing,
only and i mean only when i used to turn the a/c on, or any function that required the compressor to be on.... the idle would go through the roof!
this is such a rare problem that nobody has ever heard of and i would like to pass the knowledge along so i can save anybody else from any headaches. please add it to the tech section or wherever need be cause its a doozey!
the battery worked just fine the way it was, i've owned the truck for like 9 months now and its always started just fine, alternator did go out at one point and i replaced it but. so what really prompted me to replace the battery is that here and there it would crank the engine weak. and i looked at the age of the battery. it was old as hell! so i figured its preventative maintenance and bought a new battery thats the same 610 cca.
and it was a magic pill. and no there was nothing wrong with any of the battery terminals or cables and i didnt possibly wiggle anything that wouldve been that magic pill. the battery was the fix. and now i see why......
the alt and batt work together to power the vehicle. a/c compressor clutch requires lots of juice, and so does the fan for the cabin, especially if its hot as hell out and you turn the fan up. the battery and alternator team could not handle the load, so the computer went into some sort of mode that would crank the idle up through the roof. and then it was getting to the point where even if you turn the a/c off. the computer was still in that wierd mode. it was still telling the iac valve to go haywire. so i would then have to shut if off, restart it, and not touch the a/c. it now works like a champ and decellarates nicely too, and doesnt act like a wacko cruise control of death. (its a stick, if it was auto it probly wouldnt of been driveable.
so everybody whether you have a problem or not, and your battery is old, replace it anyway. spend the 80 bucks. because its a vital thing,
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#25
04-06-2011, 09:48 PM
1 more thing i must add.
recently as it has been warming up outside this problem was coming back only in a subtle way, and at a fraction of the bad way it was acting.
i went ahead and replaced all my o2 sensors. they were all stock, 145k miles. way overdue. the idle is now nice and steady and smooth with the a/c running and doesnt float and act like a cruise control the way it was doing.......
so battery and o2 sensors, make sure u stay on top of them folks!
they are both a part of a system that is responsible for the silly computer controlled idle and idle air control valve that these trucks have. this was a serious problem that is not listed in any of the ford manuals. and i have them all!
recently as it has been warming up outside this problem was coming back only in a subtle way, and at a fraction of the bad way it was acting.
i went ahead and replaced all my o2 sensors. they were all stock, 145k miles. way overdue. the idle is now nice and steady and smooth with the a/c running and doesnt float and act like a cruise control the way it was doing.......
so battery and o2 sensors, make sure u stay on top of them folks!
they are both a part of a system that is responsible for the silly computer controlled idle and idle air control valve that these trucks have. this was a serious problem that is not listed in any of the ford manuals. and i have them all!
#26
08-29-2021, 12:19 PM
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Well, you touched on a key that I did leave out of my previous post.
Before installing new parts I disconnected the battery, got pulled away to do some things for my wife and the truck sat with the battery disconnected for a couple days. Thanks again for reference to the re-learn procedure. I will check that out today.
I have looked at the various mounting points, engine, manual tranny, etc. Although I have not gotten into the clutch connections.
I do have a question. The exhaust on this truck is older than my ownership. If the CAT has failed in some way that partially blocks the flow of gasses, would a fresh engine still push gas through but labor in the process causing the vibration?
Thanks again PawPaw
Before installing new parts I disconnected the battery, got pulled away to do some things for my wife and the truck sat with the battery disconnected for a couple days. Thanks again for reference to the re-learn procedure. I will check that out today.
I have looked at the various mounting points, engine, manual tranny, etc. Although I have not gotten into the clutch connections.
I do have a question. The exhaust on this truck is older than my ownership. If the CAT has failed in some way that partially blocks the flow of gasses, would a fresh engine still push gas through but labor in the process causing the vibration?
Thanks again PawPaw
Cold & Warm Base idle relearn routine:
Let the engine completely cool down, turn off All electrical loads & wipe the computers memory by disconnecting the B- cable for at least 15 min, if it's hasn't already been done, or open a door, turn a light switch on, or push the cigar lighter in, to provide some resistive load to discharge the KAM memory faster.
Then turn off All electrical loads so you won't make a spark or cause an electrical surge & reconnect the B- battery cable.
Start the engine cold, let it idle down some, then slowly shift into each gear, including Reverse, long enough to feel each gear engage, ending in "N" or "P" & without touching, moving or turning anything on, let the engine fully warm up, then slowly shift into All gears again.
This will enable the computer to properly relearn its cold & warm idle strategy after a KAM memory wipe.
Ford also has a rather extensive "drive cycle" routine here Ford Motor OBD-II Driving Cycle | Car OBD Diagnostics, ECU Chip Tuning & Auto Repair Support but I've never had any driveablity problems if I perform the cold & warm idle relearn, so never have done it, or needed to use it if first doing the idle relearn routene.
One might have to do it if your trying to reset all the IM monitors, to pass an emissions test shortly after a memory wipe, or are having adverse driveability problems.
What we need to know or establish in this case is if the computer has learned the proper base no load idle strategy. If it's relearned it with the AC on, it might want to over rev the engine when the AC is turned on.
If the base idle is ok, then I was looking to try & isolate a vacuum leak in the heater/ac control panel or actuator, by having him disconnect & plug it's engine vacuum source.
If that solves the idle over rev when the AC compressor turns on, then the problem is likely somewhere in the cabin around the heater/ac control panel, or it's vacuum line connection to the blend door, or maybe it's vacuum actuator.
So thats kinda the method to my madess!!!! lol
Let the engine completely cool down, turn off All electrical loads & wipe the computers memory by disconnecting the B- cable for at least 15 min, if it's hasn't already been done, or open a door, turn a light switch on, or push the cigar lighter in, to provide some resistive load to discharge the KAM memory faster.
Then turn off All electrical loads so you won't make a spark or cause an electrical surge & reconnect the B- battery cable.
Start the engine cold, let it idle down some, then slowly shift into each gear, including Reverse, long enough to feel each gear engage, ending in "N" or "P" & without touching, moving or turning anything on, let the engine fully warm up, then slowly shift into All gears again.
This will enable the computer to properly relearn its cold & warm idle strategy after a KAM memory wipe.
Ford also has a rather extensive "drive cycle" routine here Ford Motor OBD-II Driving Cycle | Car OBD Diagnostics, ECU Chip Tuning & Auto Repair Support but I've never had any driveablity problems if I perform the cold & warm idle relearn, so never have done it, or needed to use it if first doing the idle relearn routene.
One might have to do it if your trying to reset all the IM monitors, to pass an emissions test shortly after a memory wipe, or are having adverse driveability problems.
What we need to know or establish in this case is if the computer has learned the proper base no load idle strategy. If it's relearned it with the AC on, it might want to over rev the engine when the AC is turned on.
If the base idle is ok, then I was looking to try & isolate a vacuum leak in the heater/ac control panel or actuator, by having him disconnect & plug it's engine vacuum source.
If that solves the idle over rev when the AC compressor turns on, then the problem is likely somewhere in the cabin around the heater/ac control panel, or it's vacuum line connection to the blend door, or maybe it's vacuum actuator.
So thats kinda the method to my madess!!!! lol
#27
08-29-2021, 03:10 PM
On the clogged, or partially clogged cat converter question, use your Vacuum gauge to perform a restricted exhaust test as outlined here Vacuum Gauge is an Invaluable Tool when Diagnosing Engine Problems (secondchancegarage.com) & scroll down to the restricted exhaust test scenario, to get an animated gauge idea how free flowing your exhaust system is. Other helpful trouble shooting animated test scenarios there too. Make sure Adobe Flash player is enabled, to view the vacuum gauge animation.
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