defective idle (servo) motor?

**harimon21** · October 19th, 2010 10:27 AM

Hi guys. I have not driven my lancer 91 efi for 3 days now. Whenever the engine is running idle or driving, the rpm just fluctuates nonstop like crazy ranging from 1800-2200 rpm. I suspect it to be the idle control motor (servo motor). Whenever i turn the ignition key (engine still off) i can here a mild whirring or grinding sound coming from the servo motor that does not stop. Car's drivability is crazy. also check engine light is on. How can i pinpoint that this is the cause? Any diagnostic test i can do to verify this? Motor seems to receive current, because whirring noise disappears when wiring is disconnected from it. If the motor is the problem, can it be repaired? Iead from the forum that a brand new servo motor is not cheap. Please help!

**CivicVTi** · October 19th, 2010 03:56 PM

It could just be a dirty idle air control valve (IACV), air cleaner element, or MAP sensor. It could also be a malfunctioning oxygen (O2) sensor. Have your car OBD scanned to pinpoint the problem.

**stiggmoto** · October 21st, 2010 08:59 PM

PM me sir Ts

**michaelb** · October 23rd, 2010 02:17 PM

same problem tayo, tumataas ang rpm, ano kaya ang sira?

**t2erns** · October 24th, 2010 06:20 AM

right, pa scan mo muna yung cause ng MIL (check engine light) maaring ito ang problema mo. the iac maybe doing its job para hindi mamatay ang engine mo. visually check vacuum hoses, pcv, etc.

**harimon21** · October 26th, 2010 09:30 AM

I had the idle control assembly replaced last Saturday. Now, the check engine light is gone. Idle is stable but seems to settle at around 1000 rpm. It should be around 650-850 rpm with this model. I tried to adjust the idle screw to 800 but it always seem to settle at 1000 rpm after a while. Also, the engine seems to be a little sluggish than usual, like a bad timing. Should the timing be adjusted when servo is replaced?

**tip_tipid** · October 26th, 2010 02:25 PM

timing is not affected by changing the idle control assembly.
idle rpm can be adjusted by the idle bypass screw, which normally is covered
by a plastic plug. This is not normally adjusted. The bypass shoiuld be adjusted
while the AC compressor is engaged to set the idle when the AC compressor
engages.

**dray** · October 28th, 2010 12:35 AM

I heard my mechanic once telling a car he fixed with the same conditions, he replaced the tension wires and servo motor..

**harimon21** · October 28th, 2010 12:02 PM

Apparently, when idle assembly is replaced or idle speed adjusted, the throttle position sensor should also be adjusted. I had my TPS adjusted to correct specs and presto! car is now running fine.