I have a '94 Thunderbird, with 3.8L V6.
A minute or two after starting, the engine will not idle properly -- revs
go up and down and sometimes it will stall. It does not do this
immediately after starting, or when at normal temperature. Also, if in
neutral, or if the A/C is on, it will usually idle OK.
I have also noticed that if I hit the gas pedal, the engine revs will dip
slightly before picking up. It does this always (cold, warm or hot) as
long as the engine speed is already low.
Fuel economy has dropped.
I noticed this after having a new MAF meter fitted. I have replaced the
idle speed control valve and I tested the thottle position sensor (it
seems to change resistance as the throttle is opened and there is a
steady 5v supply in the connector).
I have replaced the plugs and wires.
I attempted to test the EGR valve and, when I applied a vacuum to the
valve, the engine revs dropped (which is expected), so I don't think this
I have listened for vacuum leaks and can hear nothing (even using some
piping to help hear it). I did find one leak which I fixed, but it did not
One final note: the clock spring has failed. There are some references on
the web to this causing what looks like a TPS failure on some Chrysler
vehicles, but the explanation is due to the clockspring problem affecting
the 5v supply (which as I noted earlier, appears to be OK). I can't find
any reference to clockspring failures affecting the TPS on Fords (only
The MAF sensor was swapped out by a local mechanic after the car failed on
the way to work. The idling problems seems to start after this, although I
cannot be sure, since it idles OK if the A/C is running and that day also
marked the beginning of colder weather.
The CEL is NOT on.
Suggestions as to what might be wrong? What to try next?