Ford Repair: 1988 Mustang GT 5.0L H.O., throttle position sensor, sensor tps

Question
This car is automatic,runs great however, it has an intermttent rhythmic rolling idle at full running temp. cold start fast idle ok, as well as midtemp. Problem worse in gear at idle, when shifted into neutral or park seems to calm down. the idle rolls between 600-900 rpm, no higher or lower, and rhythmic. Does not stall. It was scanned for codes with none present. We removed the I.A.C. and cleaned. No hissing sound indicating vaccuum leaks. Spark plugs are new and are ford plugs. Also has new factory cap and rotor. I hope you can help, Iam afraid of embarking on a parts replacing expedition.

Answer
Dave-

  It sounds like your throttle position sensor (TPS) needs to be adjusted.  You can do this at home, but unless you're somewhat familiar with electrical work you might want to avoid it.  You'll find the TPS on the throttle body near the throttle cable.  You'll see 2 wires coming from it.  Take a saftey pin and poke a small hole in each wire just big enough to stick a paper clip into (unbend the paper clip first, obviously).  Then you can use a voltometer to test the range of the TPS.  With the car running and at idle it should be between 0.90-0.98 volts (if it goes over 1 volt or too far under 0.90 it'll need adjustment).  If it's out of range you can adjust a pair of screws on the sensor (but they're sensitive, so be careful) until it's within range.  Then remove the paper clips and tape over the holes with something like electrical tape and call it a day.  Hope this helps.

Steve