Engine Performance problem
1988 Volvo 760 4 cyl Two Wheel Drive Automatic 170, 00 miles
After engine reaches normal operating temperature, around 180 the engine rpm is extremely erratic. Engine rpm speeds up and down in neutral and under a load making it difficult to drive. A little history. After the volvo was driven and the engine was shut down after being hot, it would not restart. No spark. It would only start after the engine cooled down. Replacing hall sensor( distributor ), distributor cap, rotor, and spark plug wires. Seemed to fix the hot start problem. The following day I drove the car to work and I started having this erratic rpm problem after the engine got hot. The vehicle starts whether it is hot or cold, but rpm becomes erratic after engine gets hot. I have repaired several vacuum leaks, and tested engine cooling temp sensor. Resistance seems to be within range both hot and cold. I don't have the speciality tools nor the expertise required to troubleshoot other system related components. HELP!
Most likely the Idle Speed Control Motor controled by ECU. Has electric motor that moves to allow air to bypass throttle plate to keep idle steady.
On 2.3 on left side engine under intake on 2.8 back engine attached to air intake hose.
Hope this helps
Thanks for donate
May, 15, 2009 AT 7:20 PM
How do I test the idle speed control.
May, 18, 2009 AT 11:42 AM
See if motor is running and pull hoses off see if pentiel moves. Can OHM check motor see if winding good. Also check voltage to motor.