Love this car but it is making me very frustrated. I have a max speed of 50-55 mph highway and 35 around town. Engine sounds fine, transmission shifts, everything seems fine except for the fact it takes almost 4000rpms to stay at 55mph which never happened before. Just replaced spark plugs, wires, cap and rotor and no luck and no engine light or codes except for an oxygen sensor code PO172 but didn't think that would cause this unless I'm wrong. Any suggestions would be great!!!

 

not sure, just throwing this out there....clogged cat plus bad o2 sensor?
Bad o2 will make the car run rich, that hurts performance. Maybe in combo with a clogged cat.

Did the performance go down suddenly? Or has it been gradual?

Check vacumme lines.

 

performance went down gradually at first but recently pretty suddenly as you can tell by my top speed. I have read about possibly a clogged cat you think that is it? The front 02 sensor has been replaced but not the rear.

 

oh, all new vacuum lines and new pcv system just replaced also.

 

Are we talking about an 850 ?? Which engine ?? Manual or automatic ??
It would be nice if you added this info to your "signature" so when you forget to tell people it's already there.

Did you have the problem before the PCV, vac lines, plugs, wires ....

Easier way to ask would be did it start after you did something ??

4,000 rpm at 55 mph ... can you feel it shift into fourth (if it's auto) or are you in third ??
If third you have a performance issue if you're positive it's going into fourth then the trans has to be slipping.

If it's a turbo try having it running and thumb the throttle open a couple times and see if the intercooler hose from the top of the radiator to the throttle body area collapses.

 

After a streatch of highway driving, look under the car and see if the cat is RED.

 

850, non turbo, automatic, The problem didn't start until after I fixed a oil leak about two weeks ago on the cam seals. The pcv system was replaced before that. And then the plugs wires etc were replaced today. I am pretty sure 3rd gear. I would have to drive it to be sure but I think third especially because of the hills around. And for rspi, the cat didn't seem to be red when I looked. I do have code po172, possible oxy sensor and bad cat causing all this bad performance?

 

http://www.matthewsvolvosite.com/for...pic.php?t=6283

Maybe a vac line came off and it's still hanging ??

 

Thanks, ill double check the lines. Anybody else have this problem and know what it is?

 

When the cam seal was replaced...which one was it? Did you have to remove the timing belt?

 

Yes I did have to remove the timing belt.

 

Could the timing be out slightly or would it not even run if it was?