Check engine light on then off
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Joined: Jul 2006
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Check engine light on then off
I have an intermittent problem with the check engine light. While driving in town once in a while the truck runs rough for just a short time. Then the check engine light comes on for a few days then goes off. The truck runs just fine after the rough 2 minutes but the light stays on. I checked the gas cap and it's ok. I changed gas stations but no difference. Sometimes it happens then doesn't happen for another 2 weeks.
Does anyone have any idea's on this?
I drive a 1999 Ranger 4x4 3.0 auto.
Does anyone have any idea's on this?
I drive a 1999 Ranger 4x4 3.0 auto.
Moderator
Joined: Jan 2004
Posts: 13,851
Likes: 111
From: SW Va
Have the computer scanned for trouble codes & post All code Numbers, as they can offer up good trouble shooting clues. Most autoparts stores will do it at no charge if the CEL is lit.
I had this kind of intermittent CEL on my 94 3.8L Taurus about 4 years ago & found a lazy upstream bank-2 O2 sensor to be the problem when I scanned the computer. Replaced both upstream OEM O2 sensors with Bosch, no problems since. So, if you have 75k miles or more on the O2 sensors, they belong on your suspect list. Their switching range & speed slow with age, (sorta like me!!!! lol) & that can cause the CEL to come & go & if the O2 sensors PID output to the computer is corrupt enough, it can mess with fuel trim & cause driveability & mpg problems. Let us know what you find.
I had this kind of intermittent CEL on my 94 3.8L Taurus about 4 years ago & found a lazy upstream bank-2 O2 sensor to be the problem when I scanned the computer. Replaced both upstream OEM O2 sensors with Bosch, no problems since. So, if you have 75k miles or more on the O2 sensors, they belong on your suspect list. Their switching range & speed slow with age, (sorta like me!!!! lol) & that can cause the CEL to come & go & if the O2 sensors PID output to the computer is corrupt enough, it can mess with fuel trim & cause driveability & mpg problems. Let us know what you find.
Laughing Gas
Joined: Apr 2004
Posts: 819
Likes: 2
From: Northern Maine
My father's F150 acted like that. The CEL came on and the truck ran rough but it came out of it on its own within just a few minutes. It did it twice, several months apart and finally the light came on and stayed on and the truck would barley haul itself home. I hooked my scan tool up and found a misfire on #3. A new coil solved his problem.
Moderator
Joined: Jan 2004
Posts: 13,851
Likes: 111
From: SW Va
Raise the hood after dark & with the engine at idle, have a look around the #3 spark plug, wire & coilpack for arcs & sparks, or maybe try wetting the plug & wire down with a spray bottle of water, while watching for a light show. #3 plug is passenger side, firewall end of the cyl bank.
If all that checks out ok, remove the spark plug & inspect its internal insulator for chips or cracks & its electrodes condition, check the spark gap & let us know what you find.
If all that checks out ok, remove the spark plug & inspect its internal insulator for chips or cracks & its electrodes condition, check the spark gap & let us know what you find.
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