About this page
This is very much a work-in-progress. There are gaps, possibly some missing links, and certainly things that need to be added to fill it out. However, since there is about one
idle problem per digest, this may be helpful to some... Please
email me if you have any suggestions, questions and *particularly* if you find anything unclear.
Just about everything on the car can effect idle. I've tried
to limit the information for this section to problems
and components which which usually show up as idle symptoms.
If you have any addition questions, problems, suggestions, etc,
please feel free to email me.
I am particularly interested in symptom and solution descriptions
of real problems for the Real Stories of the Idle Patrol
page .
Normal Idle Behavior
The normal idle for a DSM is 750 RPM. However, due to specifications
for various components, an idle of 700-825 RPM displayed on your
tachometer can be considered normal (in the absence of
other symptoms). This specification applies to a fully warmed
vehicle with all electrical accessories switched off (except
Canadian vehicles, which have DRLs).
The car will have a higher idle under certain circumstances:
- The vehicle not fully warmed up (+0-500RPM, slowly falling)
- The A/C is on (+200-250RPM)
- The vehicle is not at a complete stop (+150-200RPM)
Idle Control
The idle is controlled by four things:
- FAIV - Fresh Air Inlet Valve
- BISS - Base Idle Set Screw
-
- ISC - Idle Stepper Control Motor
Idle Related Components
Control:
- Engine Control Module (ECU)
- Idle Stepper Control Motor (ISC)
(Idle Solenoid is 1.8L vehicles)
Sensors:
- Idle Switch
- Throttle Position Sensor (TPS)
- Reed Switch
- Cam Angle Sensor/Top Dead Center Sensor
Adjustment:
- Setting the base idle (Base Idle Set Screw (BISS))
- Throttle Cable Adjustment
- Idle Switch position
Common Idle Problems
Miscellaneous Somewhat Related Info
- The plug at throttle end of the throttle cable casing has been
known to come loose and wedge the throttle open.
- Check out the Hot
Start Problem page on Club DSM
- See some general testing info at DSM Simple Tests page.