Contour Enthusiasts Group Archives Forums General Troubleshooting Bad MAF = bad emissions?

A bad MAF can easily cause an incorrect A/F ratio since the PCM uses the MAF signal to calculate the air charge entering the cylinders. Thus, it directly bears on the 'A' in the A/F calculation. Assuming that the dealer replaces the MAF with stock, there shouldn't be any need to reflash the PCM. My guess is that he just wants to upgrade you to the latest calibration for your vehicle at the same time as he replaces the MAF. Basically, he gets paid for pressing a button and waiting around for a few minutes.

If you are still under warranty, I'd tell him to go ahead with both the MAF and reflash. If it isn't under warranty, I would want to have them read the infered barometric pressure from the PCM (or better yet, buy/borrow a scanner and read it yourself). The PCM infers BP from the MAF signal and if the MAF is bad, the BP calculation will be well off the actual BP (usually >5" low). If the BP reading is fine, your MAF is probably fine and they need to do some real troubleshooting instead of just throwing parts at the vehicle.