172 Mk1 - High Idle when engine is warm

[dru]

Hi all,

I've recently had an issue with the idle speed on my 172. When the engine is cold, the car idles at 750rpm approx. so that's fine. As soon as the engine warms up, idle gets higher and higher the warmer it gets. Today it sat idling at 2000rpm and was so high that the gears crunched a little when I had to pop it in reverse.

I noticed also that when I'm cruising in the car and I press the clutch, the idle drops down as it should, but it bounces back up to about 1750rpm, then back down to 1000rpm, then back up... it's continuous. Once I engage the clutch there aren't any issues.

What's wrong with my car? Is it the ICV or the Lambda Sensor? I can't work it out. It's definitely not the throttle sticking as it's right up on the little stopper screw.

Any ideas?

Thanks!

 

[Christopher]

sounds like an ICV problem to me...

i only say that because mine did the same. i replaced the ICV and the throttle cable. solved it on my car.

 

[Andyman]

Throttle body , leaky gasket

 

[IsvenII]

i had almost similar issue recently with my mk1 172, revs goes up and stays there when clutch is disengaged. Had my TDC sensor replaced and throttle body cleaned, car is back tip top again.

 

[dru]

is there anything that I could check quickly just to eliminate the problem down? it seems really strange that it only happens when it's warmed up.

 

[dru]

Hey all, just wanted to let you know that I found the problem! Was a slightly frayed throttle cable which was making the ICV work a little funny as it was hunting for the idle speed when the throttle wasn't completely shut. Anyway, after getting rid of the frays, it idles fine now. The fray isn't anything to worry about as it was only very slight and not worth the money to replace the whole thing.

 

[Andyman]

Replace it !!

Its a piece of piss to replace and as cheap as chips to buy.

You dont want it to snap and it WILL fray more as time goes on