Engine light on, and idles high
#1
12-06-2005, 05:56 PM
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Engine light on, and idles high
I have a 1995 F-150 with a 5.8L 351w with 230,000 miles. It seems really high but it runs great except for the fact that the check engine light keeps coming on. It idles high at about 1500 rpms and the check engine light comes on, then it idles back down and the light goes off. it does this every once and a while. it is reall a pain because when i am driving it seems to accelerate when i dont want to, and when i come to a stop it still idles high. i replace the IAC sensor and it ran beatifully for a couple days, and then the other day it did it again briefly. i also cleaned the parts of EGR (the tip of the sensor), and that seemed to help. i had the codes read at autozone and they used the old code reader with a flashing red light, and we determined that it could be either the IAC sensor or EGR sensor, but he wasnt really sure. So then i cleaned the IAC sensor with some carb cleaner and it ran much better, but it soon came back again. So i went and bought a new sensor. I dont know what direction to go next and HELP WOULD BE APPRECIATED, THANKS
#2
12-06-2005, 07:45 PM
my truck is the same year and engine and I have the same problem. i don't know if i can offer you any help, but i changed the iac sensor and the egr, but i did a tune up and a few other things and it went away. i don't know what fixed it. my truck ran good for about 2 months and the problem came back - i am also open for suggestions.
#3
12-06-2005, 11:08 PM
The only ways the idle will increase is a vacuum leak, a stuck throttle off idle position stop or a stuck open IAC.
A vacuum leak can make the OX sensor detect too lean an air/fuel ratio, shift the computer tables to the rich end and set a code.
If the vacuum leak is internittant, the tables shifts and can clear the CEL until it happens again.
You have a problem in these areas you have to look closer for and do some testing to find it.
Try to catch it when the CEL lamp is on and get a code number to give you a lead on what area is being affected.
Make no difference what kind of reader is used as long as it displays the codes.
A vacuum leak can make the OX sensor detect too lean an air/fuel ratio, shift the computer tables to the rich end and set a code.
If the vacuum leak is internittant, the tables shifts and can clear the CEL until it happens again.
You have a problem in these areas you have to look closer for and do some testing to find it.
Try to catch it when the CEL lamp is on and get a code number to give you a lead on what area is being affected.
Make no difference what kind of reader is used as long as it displays the codes.
#5
12-07-2005, 07:51 AM
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change pcv with elbow
Change pcv valve; the elbow may be cracked.
Originally Posted by Flash351
I have a 1995 F-150 with a 5.8L 351w with 230,000 miles. It seems really high but it runs great except for the fact that the check engine light keeps coming on. It idles high at about 1500 rpms and the check engine light comes on, then it idles back down and the light goes off. it does this every once and a while. it is reall a pain because when i am driving it seems to accelerate when i dont want to, and when i come to a stop it still idles high. i replace the IAC sensor and it ran beatifully for a couple days, and then the other day it did it again briefly. i also cleaned the parts of EGR (the tip of the sensor), and that seemed to help. i had the codes read at autozone and they used the old code reader with a flashing red light, and we determined that it could be either the IAC sensor or EGR sensor, but he wasnt really sure. So then i cleaned the IAC sensor with some carb cleaner and it ran much better, but it soon came back again. So i went and bought a new sensor. I dont know what direction to go next and HELP WOULD BE APPRECIATED, THANKS