What would cause my 1996 Volvo 850 non turbo to idle unevenly?

I own a 96 Volvo 850 non turbo when your driving it and giving it gas the engine runs at an even RPM but when idling the RPMs go up and down but rapidly short. I was wondering if maybe it the airflow mass meter?|||With my '94 940 (non-turbo B230fd engine /4 spd automatic w/ 134,686 miles), leaks in the exhaust system cause erratic idling. Actually, it's in the shop right now getting the exhaust manifold gasket replaced. In my case, it's either that lower 'back pressure' on the motor affects performance, or something that runs on vacuum or pressure (exhaust gas return circuit or ?) isn't getting what it needs due to the exhaust leak.





There are other causes, but this one is current for me, and easy enough for you to check... are there any visible holes/cracks/breaks in pipes or either muffler or the catalytic converter? Is it noisy? Do you feel puffs of exhaust under your car, or smell exhaust in the cabin or under the front of the car? It was also suggested to me that the catalytic converter might be plugged, but restriction hasn't seemed to affect idle that way in the past, for my Volvos anyway ('87 through '90 244 and 245s, B230f 4 spd autos). So, that gives you something simple to check. If you do find leaks in exhaust system, 'muffler tape' is an inexpensive and quick way to see if that's causing your idle problem... just tape up the holes thoroughly and see if the idle smooths out (but if you can't thoroughly cover the leak you won't know for sure). IF that did work, FIX the problem, as the metal tape won't last long at all. Keep your brick purring, man, and good luck. Hope it's a simple problem (always check those first). Just my two cents.|||It may be the MAF, they do fail, but you should have a check engine light on if that was the case.





It's more likely that there is a vacuum leak. Get a water spray bottle and spray a stream of water around the intake manifold and see if the idle speed changes. The gaskets often leak around #1 cylinder. Check the vacuum line that is right behind the power steering pump, it deteriorates and leaks too.|||most likley dirty fuel system