Originally posted by blarrr:
96 contour 4 cyl duratech vin3, 108k miles

..

CEL CODES:
-P0420 [bad cat, the light comes and goes]
-I'm pretty sure I had a light coming and going reporting that there was a misfire in cyl4 a while back. I think it got cleared when the plugs got replaced at 100k, but I'm ... Could it be the bad cat causing all the problems? ...


Welcome .
For the Zetec.
A good cheap way to test for a blocked exhaust is to remove the upper O2 sensor, and see if the performance improves. Battery needs to be disconnected before uninstalling and installing O2 sensors.

"Always do the cheap and easy ones first." 1996 V6 ATX 96K miles