93 940 turbo volvo runs only without air filter


my wife’s car with 210K wouldn’t start. i took the air filter out and it runs. i put a new one in and it ran fine for one day. it started doing the same thing so i took it out and it runs fine now. have any suggestions.


My best guess is that something associated with the air filter is causing the problem. Are there any electrical connectors or vacuum lines you need to disconnect to access the filter?


no none - my mechanic has suggested maybe the mass airflow sensor whatever that is…


Actually, I was thinking that the MAF sensor may be bad. I think that this would be a good place to start.


When you say it runs fine with no air filter, have you DRIVEN it without the filter? Or just run it? Have you experienced any loss of power during acceleration or driving?

The reason I ask is, I had a very similar situation on a vehicle I have. It was losing power and failing to start, so I began troubleshooting by removing the air filter. It started right up! Seemed to run and accelerate (just revving) fine. Then I put a new air filter in, and it was right back to not starting.

So then i tried just driving around the block with no filter, and discovered that it still had almost no power. It would RUN fine while stationary, but could not actually drive.

As it turned out, the air filter was a bit of a red herring, as the problem was actually my FUEL PUMP. The fuel pump was not outputting proper fuel pressure. I guess my theory is that with low fuel pressure at the injectors, they were just barely squirting enough fuel into the chambers to keep the thing running as long as it didn’t have to overcome the resistance of sucking air through a filter. Who knows.

Anyway, i just wanted to offer that as something to consider. You could test your fuel pressure now and see if it’s within specs. A fuel pressure guage is maybe $10, while a new MAF is $$$$. :slight_smile:

Good luck!


i just took it in the shop and my mechanic said i needed a new Constant Idle motor (CI motor). also said i had a couple of other vacuum leaks… haven’t heard of the ci motor but all told it’s going to cost me about $500…


The trouble was found; but, removing the air filter could have caused damage to the MAF (Mass Air Flow) sensor. Unfiltered air has grit, dust, and pollen in it which can damage the MAF element. MAF’s are expensive on other cars. On a Volvo, it is probably somebody’s mortgage payment! In short, DON’T run an engine without an air filter. +++ not Anon. me-art12


Try disconnecting the MAF. If that helps, I would suggest replacing it. As noted if un-filtered air got past the filer when it was changed, that could do in the MAF.


ok! they replaced the IC motor and it works great now! Just wanted all to know. thanks for all your help!