I have a 91 Pontiac Trans Am. With a blueprinted and balanced tpi 350 with 6000 miles on it. L98 heads and tpi specialties l98 super profile cam. I had superchips burn a custom chip and i have delco computer. Brand new battery, brand new msd coil, 8.8 ignition wires and new bosch platiunum +2 plugs, new accel ignition moduale. It has a flowmaster 3"catback system and high flow cat.
The check engine light comes on after you are driving highway or a constant speed for a couple of minutes and doesnt go out untill you turn the car off. If you are driveing city or just around town there is no light and when the computer was put on it no code shows up. The Air mixture gauge look slike its running alittle rich. Any ideas?

 

I'd suggest you have the person with the scan tool, monitor the ECM while driving. If the SES light coming on is repeatable, should be easy to nail down the bad parameter....then look towards repair

 

he said he did do it while he was driving and ses light was on and no code was being shown

 

Well, what he needs to do is monitor the sensor inputs, and look for one that is going out of range....not just wait for a code to set.

Is he using an actual scan tool, or just a code scanner?

 

he is using a code scanner...whatever the full computer things is with the screen and everything not the thing that you get for 29$

 

try a tech 1, chances are the after market scanner is missing something. also double check your ecm connections

 

could this be happening cause the car is coming off open loop or into open loop whicheve one happens after being warmed up?


i dont kn ow just stabbing away

 

I thought it was an open loop situation also but if i drive local streets I can drive all day with no ses light. Only when I am at a constant speend for a few minutes.