My SES light comes on at higher speeds (~60mph) .. and it stays on. I shut the car off, and it goes away. Then, when i get back up to 60, bam, on again. The car feels a little funny up there, too. I had it scanned, nothing showed up. Any opinions on whats wrong?

 

What year is it?

 

mine did the same thing, turned out to be an o2 sensor, even though it ad been replaced less then 3k miles earlier.

 

its a 94, with LT headers, hotcam, gears, cai, etc..
ive also noticed it gets real shaky up near 80MPH.. vibrates my legs lol

this happen to u too, whoever had same prob and was o2 sensor?

 

Do you still have the EGR system on the car? It seems like I read a post not long ago about a problem like this and that's what it was.

 

Yep, car ran like crap at about 55+

 

My Z did the same thing except it did set a code, it was for EGR. To test the valve pull the vacuum line off the valve, take your fingers and push up on the diaphram then plug the vacuum port on the EGR valve, release fingers. If the diaphram falls down with vacuum port plugged it is defective.

 

Are you sure it was scanned with the correct scan tool? If the light comes on, the code should be stored, as long as you had it scanned in a reasonable period of time.

 

well, the light was on, he turned the motor off, then he did some things with the pins, resetting stuff or something... u know the paperclip thing? he did the same thing only with this 2$ tool.. then he scanned. now that i think about it, wouldnt that reset the code? ahh crap

 

No.... you can NOT scan a 94 by shorting the ALDL connector pins, and no, shorting them will NOT reset the codes. 1993 was the last year you could retrieve the codes by doing that. You need to use a "real" scan tool to pull the codes.

 

Yea.. so heres an update... I was 100% sure it was EGR valve due to symptoms i read on other posts.........
then it dawned on me. I bought the car and it already had long tube headers, so the egr must be blocked off. sure enough, i check back there, and its definitly blocked off, however the EGR valve is still there. there is a little rubber nipple thing at the top. I duno if thats good or not...

So now im back at thinking this is o2 sensors. if anyone could re-read the problem i would love u forever! and ever...............

 

nobody... i know im gona get it scanned tomorrow, just wanna see if anyone had any similar problems or an early diagnosis to ease my mind.