rough idle at start up.... please help!

[beaten240]

Hello all!
I just bought a '91 240 that had a few issues. I took care of pretty much everything except a strange idle situation that comes up occasionally. It only happens sometimes, and there seems to be no rhyme or reason to it, but when you start it it will run horribly for about 30 to 90 seconds. You have to give it gas in order for it not to stall. It's fine once you get it out and about. You can stop it and restart it, and it will generally be fine. But sometimes not. It never has the smoothest idle, it's always a little lopey, nothing bad, but as i said, occasionally it will run really rough.

It generally doesn't throw up a check engine light. It has a couple times, but with no real correlation to this idle problem.

I've tried checking the Mass air flow sensor by unplugging it when idling. The car certainly notices it's been unplugged, it will race for a second, throw up a check engine light, and then run about the same as before it was unplugged.

I've also tried to check the fuel pressure regulator. I disconnected it and plugged the vacuum line coming from the intake. This seems to have no impact what so ever. Could this possibly be the problem? When i first disconnected the line i sniffed the hose from the regulator side and i could smell fuel vapors. Not sure if i was smelling them from the intake (traveling all the way through the vacuum line) or if they were from the regulator.

Sorry this is so long, but i wanted to be thorough.
Any help would be greatly appreciated....
Thanks!!!
~Nick


It should also be said that it has relatively new plugs, and it runs just fine once you're going down the road. It also smooths out fine if you keep her above 1500-2000 rpm when stationary. (as said before, will generally idle fine as well though)

The idle control valve is clean...

[billofdurham]

Welcome to Matthew's Volvo Site.

When you pulled the hose from the fuel pressure regulator did you have fuel coming out of the pipe? The best way to test the regulator is with a pressure gauge but fuel dribbling out of the pipe is a good indication of a problem.

Also clean the throttle body and make sure that the throttle position sensor clicks just as the throttle closes completely.

For more information do a search for fuel pressure regulator with the author wojeepster. Very informative.

Bill.