How to adjust my throttle cable?

Rick Lee · Rick Lee's Garage

My 993 has had low idle, rock solid at 500 RPM's, since the engine last came out 2 yrs. ago. I've tried everything with the ISV and looking for vacuum leaks. No dice. I'm wondering if the accelerator or throttle cable could be too loose now. But where is the adjustment point?

kang · 03-27-2007, 10:34 AM

Adjusting your throttle cable won't increase your idle, if that's what you want to do. The idle speed is controlled by the ECU. If your idle is rock solid, I think you're fine. The dash tack is not that accurate.

Check underneath the throttle pedal for the adjustment, though.

Rick Lee · Rick Lee's Garage

The idle is definitely low. Tach says 500 and I believe it. Wouldn't adjusting my pedal raise it?

kang · 03-27-2007, 11:31 AM

If you want to tighten your cable enough so that the throttle plate is partly open, just like you had your foot on the pedal a little bit, then maybe it would raise the idle. But these computer controlled cars are not like the old carbureted cars, when there was an idle adjustment screw that controlled how much the throttle plate stays open. The small amount of air that got past the throttle plate (due to this small opening) is what controlled the idle in those cars. In 993’s, the throttle plate closes completely at idle. The small amount of air used for idle comes from the ISV, and the computer controls how much air that the ISV allows. If you were to tighten your cable so much that the throttle plate stayed open, you would “fool” the computer. You might never be at zero throttle, according to the computer. I don’t know the ramifications of this, but I’m not sure I’d want to try it. I know the computer cuts fuel during overrun conditions (coasting at speed (e.g. zero throttle), etc). That would never happen with your idea. I also know that the computer “learns” what zero throttle is, to a degree. I tried to up my idle by tweaking the ISV. It works to an extent, but the computer re-learns what idle is and compensates. The computer might learn what you have done and compensate for it, in which case you are back to where you were.