Pony 5.0

While driving, I had the CEL flash for less than a minute. The car had just warmed up.I got home, pulled codes 41 and 91. I restarted the car and the CEL light did not come on. I took it for a spirited drive to see if it would trigger any codes and it didn't. I did a KOER and I got no lean codes. By this time, the engine was very warm. The only thing I can think of are the long tubes I am running. Will long tubes cause a false or temporary lean code?

ZachW04Stang

Longtubes won't cause a lean code. You might be running lean, try bumping fuel pressure up. Also check for vacuum leaks maybe clean the mass air out if you have time too.

samseed101

Longtubes can give codes, as they can confuse the computer. That is because of the difference in time from when a fuel correction is madeto whenthe results are detected by theO2 sensors. You should be able to have someone increase the Exhaust Pulse Delay to clear that up. Of course, that requires a chip / tune.

Pony 5.0

Thanks Samseed. I went over my car a few weeks ago and changed intake gaskets, cleaned and tested all my sensors, cleaned a dirty HEGO ground, chased down and fixed vacuum leaks until I pulled no codes. She ran like a new car after doing all that except for this CEL that comes on then goes off. I thought that since the O2 sensors were farther away than when stock, it may have been the culprit but I wasn't sure. It's off to the tuner.

samseed101

That's exactly what the Exhaust Pulse Delay table is for. Because they are further away, you have to tell the computer to wait slightly longer to read the results of it's fuel correction. Else it could be reading it too quickly and could be trying to change the fuel trim withuot knowing what is really going on. Basically ends up chasing its tail like a dog