I have a 2003 Z that has the following engine modifications: Vortech Supercharger kit, Deatschwerks 440 injectors, UTEC, front mount intercooler & Walbro 255 fuel pump.

The car was dyno'ed about three months ago and they tuned it to 375 rwhp/341 TQ at a conservative 7.5 lbs of boost. The air/fuel ratio was set at about 10/1 if memory serves me correct.

Code P0311 is the random misfire code but the car seems to run fine. The local shop I had take a look at it (not the same place that dyno'd it) said it seemed to be running very rich at higher rpm's and suggested getting the car tuned. When I told them it was tuned less than 3 months ago they told me to drive the car some more and see if the service engine light comes on. If so, take it back to the tuner and have them look at it.

Has anyone with similar upgrades experienced this before? Is the car running too rich and causing it to trip the service engine soon light while robbing me of some power at the same time? I am not very mechanical and any input would be greatly appreciated.

Jeremy

 

That's interesting because the 2003 350Z FSM doesn't list a DTC P0311. The generic definition of that code is: P0311 Cylinder 11 Misfire Detected

The VQ35 should only throw P0300 (multiple cylinder misfire) and/or P0301 through P0306 for cylinders 1 through 6.

 

That is the code he gave me and said it was a random multiple cylinder misfire. Like I said, I am not very techincally inclined and thought I would try to find some answers here.

 

does the ses light stay on always? and its vortech with an h on the end......i had that code once in a blue moon but no problems...i believe its just the ssbox on my...

 

They cleared the code and the SES light has not come back on. The car seems to be running fine.

akks350Z, any idea what air/fuel ratio you are tuned at? The guys that cleared the code thought it should be around 11/1, but I am not sure where it should be. Maybe I will get the 3.12 pulley and go back and have them retune the car. What do you think?

Thanks,

Jeremy