help! recurring problem w/ engine
 

Just discovered this forum today and wanted to get some advice/insight from you fellow users:

In the past 6 months or so, I've been having problems where the engine starts to rumble a lot harder causing the car to shake. When I stop the car and get out, I can smell a foul odor coming out of my engine. If it gets bad enough, the s80 gets to a point where it will not allow me to drive faster the 30 mph. I've attempted to have this issue fixed 3 times!

The first time the mechanic switched out my spark plugs. That seemed to fix the problem for 2-3 weeks. The same problem hit me again and I took it back. They told me now that my catalytic went bad on me. I took this car to Midas because they offered a better price on a replacement catalytic converts (OEM). That solved my problem for a month or so then I got hit w/ the same problem. Took it to a Volvo specialist and they spent a week trying to figure out what was wrong. They noticed the spark plugs were mis-firing due to the black smudges on the spark plugs. Once again I had the spark plugs replaced (they didn't think there was a problem w/ the spark plug coils). Fast forward 2 months later and it's the same thing all over again. Any ideas what's the real reason behind all these problems?

Just happened to do more research online when I got a settlement letter regarding volvo's and their faulty EMT's (not sure if this is even related).

Any ideas?

RE: help! recurring problem w/ engine
 

I would have the software for the recall done then see. Maybe a bad O2 sensor as well.

RE: help! recurring problem w/ engine
 

that's what the guy at midas said based on the codes. The O2 sensors (2 of them he mentioned) may need to be replaced. So you think the O2 sensors can cause the car to act this way? Springing up after a few weeks after a spark plug change?

RE: help! recurring problem w/ engine
 

Yes it is possible but have the local Dealer run your Vin# and see if all recalls have been done. The ETM could do that as well.

RE: help! recurring problem w/ engine
 

Thanks Tech for your assistance. I'll see if I can contact y local dealer.