Hey,

After about 10 minutes of driving my service engine light comes on and my fuel economy goes waaaaay down. I borrowed a friends innova scanner and it turned up no codes!

I know that something is wrong and that it corresponds to this light coming on. I also have a misfire or something similar around 1500 RPM. Someone figured it might be the TPS and that could be causing both problems. I know that my misfire could just be mechanical, but why would no codes turn up when the light has been coming on steady for a couple months!? Really gotta fix this fuel economy problem!

Thanks,
Cam

 

Oxygen sensor sounds like goes from lean to rich maybe misfiring cause your piston is getting not enough gas you have to get the right scanner alot come out blank a guy checked out mine with a paper clip into a scanner idk sounds weird but he did it that way my gta used to use a half tank in about 20 miles now with a new oxygen gets about 17 miles a gallon

 

Here's AutoZone's instructions for checking the codes w/o a scanner. Where they say "small jumper wire," you can just use a paper clip.

Hope that helps. Good luck!

 

I have the same problem, but my cars a 1986 and it's carbureted. CEL is on, but no codes are ever present. If i make any new discoveries while I'm working I'll let you know, could be a short in the wiring somewhere. Such as in my car where the A/C was removed one of the sensors is burned, that could cause it to turn on with no known codes.