throttle body adjustment

[crazydriver81]

Hi @ all!

I do need some help with adjusting the bypass screw for the throttle body and the idle RPM.

We connected the MUT-III computer to the car. My mate, an experienced Mitsi mechanic said, that the throttle body adjusting motor (stepmotor) displays the value 0, althouugh it shall show a value...

1 - which idle RPM value is correct, once the engine is warmed up?
2 - which value is the correct one for throttle bdy stepmotor?

Any help is much appreciated. Muchas gracias!
Stefan

[Davezj]

Not sure your question makes sense.

The values you get from the throttle body should be idle control valve (ICV), and throttle position sensor (TPS), if you have an auto you will have an accelerator position sensor (APS) as well.

Which ones are you referring to an what values are zero. By stepper motor I would assume thing will refer to the ICV.

It is just terminology but I think it will make your question much clearer.

[crazydriver81]

Dave, thanks for your hint. Yes, It is the idle contol valve (ICV) I am referring to.

[Nick Mann]

I'd aim for 750-800 rpm idle once warm. Not sure on the values for the ICV so can't help there.

[crazydriver81]

So we tried to adjust the idle RPM today...with no success. The bypass screw is fully closed and the ICV still shows 0 steps. The engine does not stall. The engine idles at 1100 RPM when warm. So the big question is, why does it not stall? Any ideas? The ICV is working.

[wintertidenz]

Are you sure the ICV is wired in correctly? It's possible that it will keep showing zero if the wiring is damaged.

[The Vee]

With warm engine, unplug ICV (stepper motor) start and see what idle is like. If it is still too high and there are no air leaks, it could be mal-adjusted throttle plate or stuck stepper. If it tries to stall, then adjust to 650 - 700rpm on throttle screw then reconnect stepper. ECU / stepper should then try to stableise rpm if stepper is working (takes a while). When all is done you may need to check TPS settings. You do need to establish that ICV / stepper is working. If it's seized you'll not get any benefit from throttle screw. Throttle plate adjustment as mentioned earlier is last resort as it is factory set.

[VOLK]

TPS 13.3% at idle? Idle switch in TPS giving you continuity with throttle closed? During cold starts, do you see the ICV step higher than 0? Have you adjusted your throttle stop screw at all? Fast Idle Air Valve has no leaks from coolant hoses?

I battled with my idle issues for ages too. ICV still does some weird stuff like hunt at idle occasionally or step to 0 at light throttle. Gave up on trying to fix it so I'm interested to see what you discover.

[crazydriver81]

Ok, problem solved. :D

The ICV was blocked by a piece of metal! I guess this came from the dead engine as we swapped over the TB. It has been definitely there for a long time already, as it was black from carbon residues. We swapped over the ICV from my old V6 N/A - perfect fit. Car is idling at 650 +/-20 RPM now and all is fine.

[The Vee]

Good news