I just bought my first VOLVO, a 91' 740SE (turbo) and moved it from a warm San Antonio, TX to 8000' and the cold of Evergreen, CO.

Sometimes, if the outside temp is below 40 degrees F I don't develop power over 2500 RPM. The car always starts, idles smoothly, but sometimes I can't get over 2500 rpm, and in neutral it's difficult to rev above 2800 rpm.

If I'm experiencing this issue, I'll warm the engine up for 5 minutes, turn off the ignition, restart the engine and sometimes the power symptons are completely gone. Other times after restart, the symptons are better, but I can't get the engine over 3500 rpm.

Other hints and attempts to fix the problem
* very average gas mileage ... ~20 mpg on the highway
* power isn't that great for a turbo, 0 to 40 mph is very average
* Replaced the fuel filter
* Replaced the fpr (fuel pressure regulator)

Thanks for any help!

Your turbo impeller could also be sticking. Keep an eye on the "turbo" gauge when you have periods of loss of power. If you can't get the needle into the yellow zone then the turbo impeller is stuck. OK to run like this but you'll definitly miss it! If this is happening occasionally now it will eventually stop permanently so start saving. It's a rather expensive fix if you can't do alot of the work yourself.

You may have a clogged cat. Broken or melted chunks of the ceramic matrix can intermitantly block exhaust flow and prevent revs beyond a couple of grand. Also you will notice a loss of power. You may also have an intake leak allowing unmeter air to lean the mixture, this would show up at cold start and perhaps more so at lower ambient temps. Check the intake and vacuum plumbing for broken split or disconnected lines. If there's a service port/plug up stream from your cat on the header pipe ... try removing it and see if the revs and power increase. That would indicate the problem is a clogged cat.

You mention un-metered air. Would a filter housing that had broken clamps possibly allow air to come in through the edges - affect this. My 760t seems to surge down at times - like it is losing power - but it picks back up in just a sec. Not near the problem that our friend has, but maybe a link?
--
'89 764 (110K), '94 940T (180K) , '92 745T (totaled 2-10-05 RIP)

The metering is done by the AMM downstream of the filter - so I dont think a loose filter would contribute to unmetered-air..

Noe