Volvo: 1988 240DL, fellow volvo owners, mixture problem

Question
We actually have a 1986, 1987, and 1988. 86 for parts as frame rusted bad.  Having problems with the 88.  5 speed trans.  When it rains or is damp it is hard to start and sounds like it is missing on 1 or 2 plugs. Once it warms up it seems to be ok but doesn't seem to have much power when going up hills. Have to downshift to 3rd gear where the 87 goes right up in 5th. We have had to replace the air mass meter 2 times over the past couple of years. The last time we used the one off the 86.  I noticed today, while the car was still running rough, that when she started up after a stop sign the exhaust seemed to have a very light brownish color to it and the car hesitated then took off and the exhaust cleared up. I noticed this as I was behind it in my car.  My wife also said that the engine would speed up slow down speed up slow down etc. when idling. It also jerks while driving at highway speeds at times.  Not consistently, can go weeks without doing it.

Any thoughts ?

Answer
This is a tough, but common situation.  It sounds like you are having a mixture problem.  Does the exhaust smell like gas when you drive the car?  There are several components that can cause these issues, including a faulty airbox valve, which is responsible for controlling the temperature of the air that the intake gets.  Also a bad oxygen sensor can feed the ECU computer a bad signal, which in turn adjusts the fuel mixture to an overly rich setting, causing some of your symtoms.  I would also think about the car needing a cleaned throttle body.  Although the symtoms tend to be more consistently bad, they do sound the same as your issue.  Because this is such a broad reaching problem, I'm also going to refer you to a great, free site called www.brickboard.com.  I suggest you post your question in the 240 section, where you'll get several responses from fellow Volvo owners.  Good luck!