Wack Service Engine Light?

Question

I have a 91' Cadillac Sedan DeVille and the service engine light turns on, however it turns off if I use the freeway and stays off for a while then will turn back on while city driving. I've had it hooked to a diagnostics machine but nothin comes up... i have no idea on why this light keeps turning on and off any ideas?

Answer 1

I would bet you that it is your intake air temp sensor.

That sensor is located in your factory air box. And when it fails it will turn on the service engine light, and turn it off, and so on and so forth.

Does this happen every time you drive the vehicle? Or does it happen when it is damp outside? When it is dry outside? Etc.

I know it is annoying, but there is probably nothing to worry about unless your car doesn't seem to perform the same way anymore.

One other thing...when the light goes on, does your car seem to idle different? If it does then I am 100% sure it is the intake air temp sensor.

That sensor would probably cost $50 or less and you can get it at a local parts store and do it yourself. It's not hard at all to replace.

Answer 2

something is tripping a code but clears itself on highway driving or when key is cycled. these are known as soft codes. most commen on gm is o2 senser rich or lean.to find out get your mechanic to drive it with his scanner hooked up. or to agree to scan it imediately when you come in with out turning the key off and clearing the code. this has worked for me in the past.

Answer 3

That's wack.

It's probably getting too hot durring city driving.