I have a 1992 Volvo 240 station wagon, 208K miles. Car runs well and has been reliable, except recently has started to idle rough when the engine is hot. Car starts fine and will idle fine for about 10 min (longer in colder (less than 30 degree) weather. Car runs fine at cruising speeds and rough idle clears if you increase engine speed even slightly. Cleaned throttle body, replaced air filter, ran cleaner through the fuel system. Computer shows diagnostic code 2-3-2 "computer compensating for rich or lean mixture at idle. Air mass meter is checking out with correct resistance. Any advice appreciated.

 

MWL- sounds like my 89 240DL wagon. I cleaned out the idle valve (see a post I submitted about a week ago) it's a thing about the size of a 8 oz can under the intake manifold. Cleaned it out and now she idles (hot) fine. I've got the same code on my engine light too. Is your car blue? Dave

 

Thanks for the suggestion about cleaning the idle control valve Dave. I cleaned the valve and it did help with the idle performance. I also cleaned the throttle body, replaced o-rings on the injectors and all helped some. Over time though, the idle got rougher again, computer would through a "failure in signal from the air mass meter" and "failure in signal from fuel injectors". Turns out that there was one primary problem that was the root cause, a broken intake manifold gasket! To diagnose,
spray carb cleaner around just about everything in the intake side of the
engine. When you hit the spot where there is a leak, the engine smooths
out. Now, the engine runs as smooth as when brand new.