W126 Hunting at idle in Park only.

[matsmith]

My 88 420SEL has started hunting when idling in park only. I have searched the various threads but got mixed messages. There is only a slight fluctuation in revs but it is quite noticeable. The car performs fine other wise.

Is there any way of testing the Idle Control Valve?

Any help appreciated.

 

[opps-man]

This sounds like a perished air feed pipe. try checking the many small rubber tubes that are connected to the fuel injection system solenoids and relays.
I had a similar problem last year and it turned out to be a perished solenoid tube. total cost of repair £1.20.
Only effected the running when at tickover when demand was low,as soon as demand increased then the vacume effect closed the rip in the pipe.
Hope this helps.
Don.

 

[matsmith]

Thanks, I will have a look this weekend.