Contour Enthusiasts Group Archives Forums General Troubleshooting Poor mileage/rough idle

Last summer, I replaced the MAF sensor after CELs, rough idle, stalling at stoplights, poor mileage. The MAF was defective, and the same thing happened again, so I returned and replaced the MAF again.

Six weeks later, I have the same symptoms, except no CEL. Mileage has dropped from around 28 mpg to 19 mpg (same driving patterns), the car nearly stalled at a stoplight earlier this week, and it had a rare hard start yesterday morning.

Any ideas for things to look at or fix?

I had bad idling, IAC was changed last February, and it improved somewhat. Symptoms returned again,two weeks ago .. the culprit was thought to be the same again, but it turned out to be the upper intake gaskets, which on the '95 V6 Duratec were about CDN $14.00 each ( 2 required) and about CDN $85.00 for labour.
Before having the car serviced I had put in a bottle of fuel cleaner and had reset the computer by disconecting the battery for 10 minutes and had the idle 'relearned', but that only lasted for about half of a tank of fuel.

Even though the CEL is not on, have it checked for codes.

Normally the only reason it could get that bad and have no CEL is if it was not reaching closed loop operation (ie. bad coolant temperature sensor or MAF not plugged in).

Vacuum leaks, IAC, MAF, or intake air temperature sensor could be responsible too, but also check the plugs and wiring.

Running diagnostics on the car ($100) will show if the computer is getting bad information from one of the sensors.