I have a 1990 Volvo 740 wagon.It's a non-turbo , but it's a regina.Since I purchased it about 6 months ago it has had a sputtering problem on take off.I used to be a volvo tech which is why I searched for a volvo but I never worked on a "regina" , I have replaced plugs , crank sensor , timing belt and seals , fuel pressure regulator , O2 sensor and a few more parts to see no remedy , if anything the problem is getting worse.I recently had to replace the resonator and found pieces of the catalytic converter in it , waqs wondering if anyone knew if the regina is sooo sensitive to back-pressure if the cat could be the cause , any ideas would be greatly appreciated.

 

Regina is not known for any problems in particular besides the parts being a little scarcer, and so costlier. Any codes? I'd look at other culprits for that "sputtering" problem you are having. You have done a tune up and a timing belt but there are other possibilities... fuel pressure? MAF? That coil itself (or its ground), etc...

 

Make sure that there are no cracks in the dizzy cap.