Check engine light came on

Buddy - pickup a scanner and read the code(s) first. OBDII is very good at providing useful codes.

 

I have this one and it seems to be fine but I don't have broad experience with other makes and model scanners.

https://www.amazon.com/Actron-CP9125-PocketScan-Code-Reader/dp/B0007LEG2K?tag=comparetables-20

 

They will all work more expensive ones oftain have feature that wont work for our cars anyway.

I have a couple and the 50 dollar range gives you what you need usually.

My guess is an o2 sensors is bad, its quite common bu pick one up and try it.

What kind of exhaust, muffler, cats are you running??

 

Don't bet on it

 

That has never happened for me!!

Tell us why its throwing the code and then just fix it.

 

Now here's one of several reasons why an F355 Challenge is so much fun. My 1995 always throws check engine lights for both banks. Prior to its major service three years ago, it was the Check Engine 5-8 light that would come on when the car was idling or moving slowly. It went off when I picked up speed. The light for the 1-4 bank came on occasionally and behaved like the 5-8 bank light. After the major service, both lights come on within five seconds of each other and go off the same way when I pick up speed.

I guess my engine is properly balanced now.

 

So have you bothered to check the codes? Sounds like possible vacuum leaks.

 

No, we haven't bothered doing that. I was told to ignore the lights as it has something to do with the way the ECUs were flashed when the car was tuned. My car retains its catalytic converters and has its (valve-less) Challenge exhaust. The car idles rich and leans out with engine speed.

Check Engine lights behaving this way is common amongst Challenge cars.

Here are the dyno graphs with air/fuel mixtures...

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So the ecu in buddys car is not stock then??

 

That is certainly rich at idle. Do you know why they tune it that way?

Different car.

 

Get this and Dash Command app for your phone or tablet.

Lot of useful things like fuel trim logging, etc.

https://www.amazon.com/gp/aw/d/B01L8XCP14?psc=1