Kinda wierd.... maybe its happened to you guys?

[DeLo360]

Recently, i replaced my bad 420A motor with another one that had the same milliage as my car.... 78K. Anyway, after it is all said and done, the car runs really well. Probably better then the first motor. No problems there. A day later, my service engine soon light comes on when i am on the highway. Ok no biggy... it takes about a week before i can get together with the guy that put the motor in. During this week... i found out something very interesting. When i drive my car around town for a while, the light goes out. As soon as i get on the highway for more then 10 or 15 minutes, the light comes back on. On the day i meet the guy to get the computer scanned, my possitive batter terminal must have gotten loose b/c i had no power. I poped the hood... jigled it back into place, and my car started up fine again. But b/c of this, my computer got cleared. So when we read it with the reader it showed no errors. But while he was there he checked my O2 sensors on his reader, and they worked perfectly. In fact we could track exactly what they were doing as we applied more throttle. Also, i replaced one of them last year... so i know at least one of those cant be the problem. So this is where i was. My car ran perfectly, but that light would still come on when i was on the highway. I finally stopped by autozone when the light was on, and got them to scan the computer. It gave out two errors..... Both the oxygen sensors. So this is where i am....

Car runs fine.
I checked the gas cap.
At least one O2 sensor is new.
My friends reader showed them working in action.
Autozone reader says they fail.
Light only comes on the highway.
And goes out in city driving.

Only thing that is not right with the car, is that one of the belts has a speratic squeek at higher rpms, but not idle. I cant id which one it is yet, b/c it only happens when driving. I'm just goin to buy some belt dressing and see if it makes the squeeking go away. But i dont think that would cause the light to come on. Thanks guys, Dave

 

[IceDragon]

Check your connections man, because my light came on in my 1g before at times for no reason other than i had some wire that jiggled itself loose than would just magically jiggle itself back on... it was some weird stuff, but, yeah, just check all your wires, make sure they are wired on tight.

 

[DeLo360]

Yeah it might be somoething with the wiring. The only thing that makes me think otherwise though, is that the light comes on the high way like it is its bible. After being on the highway for 10 minutes... i would bet my life on that light comin on. Its a little to regular for wires to be out of place. Oh... and i just passed inspection like a week ago... so my O2 sensors have to be working... right?

 

[Thunderskull]

What is the exact code that you are getting? The fact that they come on only at highway speeds might be because you are flowing more air/exhaust at that time thus you're flowing more pollutants through your exhaust system. For us to better help you we need to know exactly what the engine codes were.

 

[DeLo360]

crap... they didnt give me the codes... well its off to autozone i go... again.

 

[neowave2109]

yea i had the same thing happen to me in a mazda turns out it was the o2 sen and the cat was backed up... well < burnt > cause i spryed nos but that was my problem