Hi Fitz, I appreciate very much your information on the IAC on the B230F and other engines.

My question is that my 1993 940 B230F with 140K miles has an idle surging problem.

The local Volvo shop where I get my work done has cleaned the IAC and said that the car's computer is now likely at fault as he "has four or five computers and the idle circuit is dead". A new computer from this shop is about $900 installed. Does this sound plausible or does the IAC need cleaning some more?

The mechanic, who has been tremendously reliable and honest for some years now, cleaned the IAC, he also cleaned the throttle body and put a bottle of LubroMoly Ventil Sauber directly into the vacuum line at the front of the injector rail and "burned the carbon" off the valves. After this, the car ran very smoothly for about 3 weeks, but the idle is now surging up and down at 500-800 rpms when I put the car into gear or when I turn on the AC.

Please help and advise as I'd rather put in a new IAC myself for $150 from FCP Groton than a new computer at $900 !

Thanks so much,

Lee in Central Florida
--
'93 940