what causes idle fluxuation
#1
05-21-2006, 08:15 PM
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what causes idle fluxuation
the TPS and IAC have been replaced. i have not found any vacuum leaks. what's the deal? the motor starts right up and idles at 700 RPM's.
in park after it idles fine for about 1 minute then the idle starts to fluxuate back and forth, high, low and they keep building up on top of each other; the high idle keeps getting higher and the lower idle keeps getting lower. the lower idle keeps getting lower until the motor stalls out.
it also does this in drive. this is no good if i'm sitting at a stop light. BUT it starts right back up after it dies AND IT IDLES FINE.
it will do this again when it's idling for that minute of time at another stoplight or parking lot.
WTF
code shows a faulty knock sensor. but i have no idea how the knock sensor has anything to do with idle. unless it actually does?
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in park after it idles fine for about 1 minute then the idle starts to fluxuate back and forth, high, low and they keep building up on top of each other; the high idle keeps getting higher and the lower idle keeps getting lower. the lower idle keeps getting lower until the motor stalls out.
it also does this in drive. this is no good if i'm sitting at a stop light. BUT it starts right back up after it dies AND IT IDLES FINE.
it will do this again when it's idling for that minute of time at another stoplight or parking lot.WTF
code shows a faulty knock sensor. but i have no idea how the knock sensor has anything to do with idle.
unless it actually does?<!-- / message --><!-- sig --><!-- / message --><!-- sig -->
Last edited by bluneon; 05-21-2006 at 08:18 PM.
#2
05-21-2006, 08:18 PM
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#4
05-21-2006, 09:36 PM
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Believe it or not bluneon, I had an oxygen sensor doing the same thing, but it was causing my air charge temp. sensor to foul and make the idle off. I'm not sure but the O2 sensor may give off an emissioncode. Also try checking the EGR. It could be full of crap and just need cleaned out. Also a very strong candidate for this is the EGR valve.
Last edited by Iron Horseman; 05-21-2006 at 09:41 PM.
#5
05-22-2006, 01:54 AM
This seems to be THE most common problem with F trucks. How many have trouble with this ! Mine does the exact same thing and also knocks under load unless I remove the shorting bar off the distributor. Its not an exhaust leak and the EEC wont give me any codes at all ! Have it booked in with Ford dealer on Friday for a dyno diagnostic. Will post you Fri arvo and let you know what the mechanic says it is. Meantime, I'm buying a push bike :P
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05-22-2006, 01:55 AM
#7
05-22-2006, 07:12 AM
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#8
05-22-2006, 11:37 AM
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My 88 F250 was doing the same thing you describe. Try cleaning the throttle body with some cleaner and a small brush. Although this didn't solve the problem with my truck it may work for you. I ended up having a new throttle body installed. It was a little pricey but it solved the problem. Good luck.
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05-22-2006, 03:20 PM
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so i had the motor running in park. i had my timing light flashing on the crank damper with the advance adjusted so that i can get the mark lined up with the pointer. when the idle started to fluxuate i tapped the motor with a hammer to simulate a knock. i was expecting to see the timing advance/retard to try to compensate for the simulated knock.
but the motor died RIGHT after the tap. there were no idling back and forth issues. it just died on the spot. well...at least i know somehow the knock sensor is still working
but the motor died RIGHT after the tap. there were no idling back and forth issues. it just died on the spot. well...at least i know somehow the knock sensor is still working
#10
05-22-2006, 03:50 PM
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05-22-2006, 07:13 PM
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KOEO showed 2.48 Volts going to the knock sensor. this is within the RANGE: 2.4-2.6 Volts it's supposed to be. (boy was it a bitch to get to....) so that means the computer is communicating with the knock sensor.
now the motor dies regardless of idle situation when i do the hammer test. it could be idling normal and i tap the motor and it will die or at least the idle will drop considerably. and i'm not able to see if the timing changes at all cuz the motor just craps out....
now the motor dies regardless of idle situation when i do the hammer test. it could be idling normal and i tap the motor and it will die or at least the idle will drop considerably. and i'm not able to see if the timing changes at all cuz the motor just craps out....
#12
05-23-2006, 02:29 AM
Ive searched some other forums and found that alot of them with similar problems like ours recommend cleaning the EGR. That prolly wont hurt to do so as im tryin to fix her on the cheap. I will try it tommorrow and keep you guys posted. Oh btw when this happened it was a sudden thing not a steady degradation. Thanks Tony
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05-23-2006, 09:23 PM
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05-25-2006, 01:41 PM
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i'm reading over www.fordfuelinjection.com and this is what i found:
KOEO:
81 air mangament circuit 1 malfunction
82 air managment circuit 2 malfunction
KOER:
44 thermactor AIR sys System inoperative right side
25 Dyn Responce Test Knock sensor not detected
no one seems to know what exactly codes 81 or 82 are. i bought the truck without the air pump and it has no cats.
Warm Idle
This one tends to be more about emissions. Warm idle occurs if the engine starts and ECT rises above 185°F, we come up to a stoplight, or place it back into neutral. The computers is programmed with a target RPM for idle, typically it’s around 672RPM. Typically the computer is struggling to achieve its target RPM. 255°F is the magic number to start complaining about overheating. Let’s break it down by system. Fuel is now closed loop with HEGO switching. We are now aiming for 14.7:1 A/F ratio for perfect emissions, enrichment will occur only if the ECT is above 225°F. There will be no EGR operation at these RPM’s. Timing is mildly advanced and will begin to retard after a minute. We need hot exhaust gasses to help complete combustion and converter operation. Air is pumped into the converter, but will dump to the atmosphere after several minutes to prevent overheating the converter. The Throttle Air Bypass will be controlling idle, we need a nice smooth idle. Not to high with A/T transmissions to prevent creep at stoplights. Idle will increases 100-200RPM if the ECT or ACT is over 225°F. This RPM increase will help burn the rich mixture cooling the combustion chamber. The faster RPM speeds up the accessories, specifically the water pump and fan. Belt fans will speed up, and electric fans will need more juice from the alternator.
This one tends to be more about emissions. Warm idle occurs if the engine starts and ECT rises above 185°F, we come up to a stoplight, or place it back into neutral. The computers is programmed with a target RPM for idle, typically it’s around 672RPM. Typically the computer is struggling to achieve its target RPM. 255°F is the magic number to start complaining about overheating. Let’s break it down by system. Fuel is now closed loop with HEGO switching. We are now aiming for 14.7:1 A/F ratio for perfect emissions, enrichment will occur only if the ECT is above 225°F. There will be no EGR operation at these RPM’s. Timing is mildly advanced and will begin to retard after a minute. We need hot exhaust gasses to help complete combustion and converter operation. Air is pumped into the converter, but will dump to the atmosphere after several minutes to prevent overheating the converter. The Throttle Air Bypass will be controlling idle, we need a nice smooth idle. Not to high with A/T transmissions to prevent creep at stoplights. Idle will increases 100-200RPM if the ECT or ACT is over 225°F. This RPM increase will help burn the rich mixture cooling the combustion chamber. The faster RPM speeds up the accessories, specifically the water pump and fan. Belt fans will speed up, and electric fans will need more juice from the alternator.
- it states that there will be no EGR operation at warm idle so whether this is clean or not doesn't matter it seems.
- after this minute of idling the timing will retard, sounds very strange as my truck starts fluxuating it's idle after this minute of time!
- the IAC is now controlling idle: but my IAC was tested within 7-13 ohms and has had a bunch of carb cleaner sprayed onto it. i have since returned the new IAC cuz 60 bucks is alot of money if it doesn't help my idle problem.
KOEO:
81 air mangament circuit 1 malfunction
82 air managment circuit 2 malfunction
KOER:
44 thermactor AIR sys System inoperative right side
25 Dyn Responce Test Knock sensor not detected
no one seems to know what exactly codes 81 or 82 are. i bought the truck without the air pump and it has no cats.
Last edited by bluneon; 05-25-2006 at 01:45 PM.