M20b25 Tuning.

[max]

Hi,
Has anyone got any good links to tuning info? My m2b25 is idling fast, and I don't really know where to start.

Also does anyone know a good place to take it too, to get it set up to its best, maybe on a rolling road? Bearing in mind I'm in Cardiff.

Cheers, Max

[Jeroen]

Start with a check on function and adjustment of the TPS (3 way throttle position switch) and TB base setup. Somehow people think they need to adjust the TB to adjust idle.

[nuke laars]

Further to Jeroen's comment, you need to ensure that that the TPS microswitch clicks when the throttle is at its rest, this send a signal to the ECU to use the idle setting.
People blindly mess with the throttle stop screw, thinking that it will adjust the idle, it doesn't.

[Eddie.]

I also have a high idle on my M20B25.

I can only echo the above comments, ensuring the TPS is working correctly. It's not uncommon for them to get gunked up with oil. Take it off, check it, check it with a multimeter that it's getting the correct signals, and refit it correctly. E30Zone/Google search will give you the information you need.

This didn't actually fix it for me, so I now believe it is a small vacuum leak, potentially on the inlet. It's on my list of things to do.

[luke]

The quick and dirty way to check the TPS is to just to unplug it and run the car - if idle is higher than before, and then drops back to what is was with the TPS plugged back in, the TPS is working, if the idle stays the same whether the TPS is plugged in or not, then it's not working.

Presuming you have motronic injection, sometimes resetting the computer by removing the negative lead from the battery with the headlights on and leaving it for a few minutes will help with strange minor issues too.

[Jeroen]

You can also take a multimeter and measure if it switches (just measure resistance on the pins with the connector disconnected). The setup is pretty simple with tree wires, it should switch at idle and at WOT. Usually the switch is clogged internally, or the TB is maladjusted. In both cases it doesn't switch back to idle again. Not saying this is the only cause but it is a simple check and a very common issue.

But as always, a little more info is more than helpful, like when the issue started, what work or mods were done, any other issues, etc.