Engine light...

[muleskinner]

I know this has probably been discussed before hundreds of times & searching it seems to be overwhelming with thousands of post and trying to find the exact one.
But any who, I replaced the manifold and down pipe and used the same oxygen sensor. The welder guy got it out of the old manifold by heating it up and screwing it out. Maybe by heating up the sensor, it damaged it.
I also put a manifold gasket on and a down pipe gasket. I didn't use any gasket sealer cause I couldn't find any info to have to use any.
I drove it all week and the engine light only comes on when I'm at cruising speed (40 to 65 miles an hour). When I slow down the light goes off. It doesn't effect the performance or running of the car. Maybe in time the light will not come on.
The engine light has never come on before this. Even when a hole developed where the down pipe and manifold meet (that's why I replaced them, too corroded to fix).
Someone must have had that happen and maybe found the fix. (I know put a piece of electrical tape over the engine light, LOL) Anybody know what it could be?
Thanks in advance,
Mike

[muleskinner]

Ok, remembered there is an "advance search" and have an idea that it might be the 02 sensor. I have to check the codes first to make sure.
I don't have a catalytic converter on this Festy anymore, so that could be it too, but like I said the light never came on before I changed out the manifold & down pipe.

[WmWatt]

You can take the O2 sensor out and heat it to red to hot clean it so I suspect heating the manifold to remove it would do no harm. That isn't to say it can't be harmed in other ways. Have you checked the wires and connections? Sorry I don't know what might cause the check engine light to come on intermittently.

[tooldude]

Even without all the facts, circumstantial evidence given points to a failing O2 sensor or maybe the possibility of the manifold leaking. Sounds like an old & failing O2 sensor - typical behavior.

[muleskinner]

Well, I cannot get a code since the engine light only comes on when I'm going at least 40mph cruising speed. When I lift off the pedal just a tiny bit it goes off. Then comes back on after a while at cruising speed ..... Then I can let off the gas pedal a tiny bit again and the light will go off again. The car runs fine so it must be a bad 02 sensor.

[TorqueEffect]

Definitely an o2 sensor. Mine did the same exact thing back when I was still running the stock engine.