Questions and Answers
Ford Escort Air Bypass Valve
Q. I have a 1991 Ford Escort GT with the 1.8 liter DOHC, 5 speed, and 114,000 miles. Normal rpm is about 700 to 750 and when it warms up it always has gone to this. I was driving to work and everything was normal then at a stoplight it jumped to approximately 1,300 rpm and has stayed at 1,100 to 1,400 rpm ever since (Hot or cold).
It has new temperature sender/sensors, new O2 sensor, new TPS and no codes. No vacuum leaks found. Was told by Ford it was the IAC. Book says 6-14 ohms, I get 9.6 when I measure it. can it still be the IAC? Wouldn't the bypass air valve still be working when the engine is cold? They tell me it is stuck and will cost $460.00 for the part, over $600.00 installed. Car seems fine other than the idle.
A. Before replacing parts, I would suggest giving the throttle body a good cleaning. About 75% of the time this alone will get rid of any idle problems.
Recommended Cleaning Procedure:
CAUTION: DO NOT use this cleaning procedure on the Nippondenso Idle Air Bypass Valves (above). These valves may be identified by their black plastic housing, and by a yellow and black warning label affixed to the valve housing and/or the throttle body. Nippondenso Idle Air Bypass Valve service is limited to replacement only.
- Remove the Air Bypass Valve from the vehicle.
- Remove the electrical solenoid assembly from the mechanical portion of the Air Bypass Valve by removing the two screws, then sliding the mechanical portion away from the solenoid.
- Soak the mechanical portion in carburetor cleaner. CAUTION: Do not exceed three minutes soak time, and do not use choke cleaner, as an internal O-ring may begin to deteriorate.
- With the mechanical portion completely submerged shake in all directions. Then push in on the rod that mates with the solenoid assembly, and again shake in all directions with the unit submerged and the rod held in as far as possible.
- Remove the mechanical portion from the cleaning fluid and dry out thoroughly using shop air.
- Assemble and install the valve.
- Check idle speed.
Cleaning Throttle Bodies 
