Idles up and down then dies
#1
09-30-2004, 08:39 PM
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Idles up and down then dies
90 f150 4x2 I6 efi 4spd dual tanks
Sorry for the spelling. heres my story.
ok i replaced my egr position sensor last week. my truck was trying to buck a little. well i never cleared the codes from the computer so today i was doing some home repairs and fired the truck up let it run for bout 15 to 20 minutes, then shut it off. and took the neg battery terminal off hit the brake to kill any stored sensors. hook it back up bout 10 minutes later. started the truck to head out to the hardware store.
Well then the truck started to idle from 700 rpm's to about 200 rpms would do it 3 or 4 times then would die. started right back up then done the same crap again and is still doing it. couldnt pull any codes. anyone have a clue what would make it idle up and down then die ? going down the road it runs good. if you push the clutch in for a few seconds it will die.
sorry for the long drawn out story but id really appreciate all the help i can get
thanks in advance
Sorry for the spelling. heres my story.
ok i replaced my egr position sensor last week. my truck was trying to buck a little. well i never cleared the codes from the computer so today i was doing some home repairs and fired the truck up let it run for bout 15 to 20 minutes, then shut it off. and took the neg battery terminal off hit the brake to kill any stored sensors. hook it back up bout 10 minutes later. started the truck to head out to the hardware store.
Well then the truck started to idle from 700 rpm's to about 200 rpms would do it 3 or 4 times then would die. started right back up then done the same crap again and is still doing it. couldnt pull any codes. anyone have a clue what would make it idle up and down then die ? going down the road it runs good. if you push the clutch in for a few seconds it will die.
sorry for the long drawn out story but id really appreciate all the help i can get
thanks in advance
#2
10-01-2004, 09:03 AM
Removing the battery cable clears the codes OK, but it also clears the KAM.
(Keep Alive Memory). The computer loses all the experience it has built up controlling the engine in your particular truck. (It stores adaptive corrections it has picked up from closed loop mode, and can apply them to open loop situations like cold idle). In some engines, it "learns" the idle speed at the end of the KOER test, and uses this to control the IAC. This is also cleared when you pull the battery cable off.
There are times when you want to clear the whole computer out like this (engine rebuild, cam change) but generally it is better to clear only the memory codes. For future reference, to clear out only the continuous memory codes do the following:
key off.
Install jumper to start a KEOE self test.
Key on.
When the codes (or the 1-1-1 pass code) start flashing, remove the jumper.
Key off.
One thing I would check is the EGR passages and the seating of the valve. It is possible that the EGR valve is sticking open. This may have caused the bucking, the stored memory code, and is now causing the idle surging. The computer may have been able to compensate for the egr leak at idle, until you cleared the KAM by removing the battery cable. The computer may be able to relearn the characteristics of your engine if you drive it around for a while.
In any truck this old, check the quality of all of the grounds (battery cable, chassis ground, etc.). I learned this the hard way...
(Keep Alive Memory). The computer loses all the experience it has built up controlling the engine in your particular truck. (It stores adaptive corrections it has picked up from closed loop mode, and can apply them to open loop situations like cold idle). In some engines, it "learns" the idle speed at the end of the KOER test, and uses this to control the IAC. This is also cleared when you pull the battery cable off.
There are times when you want to clear the whole computer out like this (engine rebuild, cam change) but generally it is better to clear only the memory codes. For future reference, to clear out only the continuous memory codes do the following:
key off.
Install jumper to start a KEOE self test.
Key on.
When the codes (or the 1-1-1 pass code) start flashing, remove the jumper.
Key off.
One thing I would check is the EGR passages and the seating of the valve. It is possible that the EGR valve is sticking open. This may have caused the bucking, the stored memory code, and is now causing the idle surging. The computer may have been able to compensate for the egr leak at idle, until you cleared the KAM by removing the battery cable. The computer may be able to relearn the characteristics of your engine if you drive it around for a while.
In any truck this old, check the quality of all of the grounds (battery cable, chassis ground, etc.). I learned this the hard way...
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