What is the most likely explanation for a check engine light that comes on for a few days, then goes off for a few days, then back on, all with no intervention on my part? Plugs/wires are new. O2 sensor? 2000 4-cyl OBW, 105K.

Well there's one way to tell for sure: get the code read. Autozone etc will read it for free. Even if the light isn't on currently, it doesn't matter: the code will be in the history. Anything else is simply guessing, but a common cause (esp. if no apparant driveability issues) is P0420 catalyst efficiency.

 

Also I"m sure you know you're right at the timing belt replacement interval if it hasn't been done already.

Like he said get codes checked, but if i had to make a guess one of two things, misfire (plugs wires) or the front o2 sensor.

 

On my 2.2L Legacy i got a check engine light at the timing belt interval. Changed the belt it went away. I cant find any documentation to prove it, but what we guessed was the cam sensor and crank sensor got slightly out of synch and threw a code.

 

nipper

Right on nipper. Good info on the 2.2.

I get an intermittant CEL on my '98 OBW. I've checked a number of times and there is never any code in the history. No problems noticed with the exception of some small bubbles in the coolant overflow reservoir.

 

Oh oh. :-\

 

John

Milwaukee

Hm..maybe not all codes go into history. What kind of code reader are you using? I can double check I was pretty sure when I hooked up my cheap pepboys actron scanner it showed some of my previous codes.

 

Maybe you could drive around with your code reader connected so you can pull over when the light comes on and scan for codes immediately?

Not all codes are stored.

 

Also if the problem corrects itself that code will be erased.

 

 

nipper

I get an intermittant CEL on my '98 OBW. I've checked a number of times and there is never any code in the history. No problems noticed with the exception of some small bubbles in the coolant overflow reservoir.

 

Oh oh. :-\

 

John

Milwaukee

 

You should get a block check done to check for any emissions in the coolant. If it is a problem it is best to repair it ASAP.

Oh oh. :-\

 

John

Milwaukee

 

Uh oh is right

 

nipper