Check engine light
Thread Starter
1st Gear Member
Joined: Jun 2004
Posts: 83
Check engine light
Has anyone experienced this before?
sometimes my check engine light goes on but it never stays on for any real length of time. For example yesterday on the way to work I drove for about 20-25 min on the highway and the CEL came on, it stayed on for the next 30 min or so. Pulled into the parking lot shut the car off started it up immediatly and the light was off. On the way home drove for 40min light came on but went off in under 2 min. It hasn't lit up in the city but that is mostly short trips, under 20 min.
I was thinking 02 sensor or air flow sensor is bad? But why would it go on and off?
Car history: '91 mustang 2.3 5 speed. Replaced head & gasket 2 months ago. Gasket went filled cyl with oil and antifreeze (long story). I understand the 02 sensor should have been replaced after the gasket was changed but IF the sensor was gummed up with oil or antifreeze wouldn't it fail all the time? Why only some of the time, highway speed, long running time etc.....?
I would have it checked but I was told if the light is not on then the test would come back normal and as I said it never stays on and if I shut the car off the light goes off???
sometimes my check engine light goes on but it never stays on for any real length of time. For example yesterday on the way to work I drove for about 20-25 min on the highway and the CEL came on, it stayed on for the next 30 min or so. Pulled into the parking lot shut the car off started it up immediatly and the light was off. On the way home drove for 40min light came on but went off in under 2 min. It hasn't lit up in the city but that is mostly short trips, under 20 min.
I was thinking 02 sensor or air flow sensor is bad? But why would it go on and off?
Car history: '91 mustang 2.3 5 speed. Replaced head & gasket 2 months ago. Gasket went filled cyl with oil and antifreeze (long story). I understand the 02 sensor should have been replaced after the gasket was changed but IF the sensor was gummed up with oil or antifreeze wouldn't it fail all the time? Why only some of the time, highway speed, long running time etc.....?
I would have it checked but I was told if the light is not on then the test would come back normal and as I said it never stays on and if I shut the car off the light goes off???
Joined: Feb 2005
Posts: 40
From:
RE: Check engine light
The check enging light will come on and off to remind you that there is a stored code in the computer. It may not be an "active" code which means that the problem is happening right now. It is probably an "inactive" code which is just info on a previous problem. It still needs to be checked out though.
3rd Gear Member
Joined: Feb 2005
Posts: 542
From:
RE: Check engine light
Geez....AutoZone....I cringe just thinking about that. A 91 has an OBD-I system. Very easy to check the codes. You need to locate the EEC test connector under the hood. Mine is a 94 and it is located behind the right hand suspension tower. Any Haynes manual or other will tell you which terminals to jump in the connector. Then all you have to to is turn the key on with the engine not running and watch the flashing of the engine light. It is a good chance that it is an O2 sensor...they often act intermittantly when they are on their way out.
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