90 Volvo 240 DL Stutters/bucks at 2500 RPM

UpstateNY · Post by **UpstateNY** » 09 Jan 2008, 10:41

The title about says it all. In any gear (5 speed manual), and only between 2000-2500 rpm, there is a subtle stuttering/missing/bucking-whatever one could call it. It isn't an extreme sensation but it is sufficiently noticable to be irritating. Acceleration, performance or mpg do not seem to be dramatically affected. Acceleration from 2500 rpm is normal. It's just when I am driving at constant speeds ranging from 2000-2500 rpm. I must say, in 5th gear it is less noticeable-but I attribute that to speed. I just replaced plugs, rotor, cap, and air filter to no avail. Oil and flame trap are recent also. Vacuum lines are clean and attached. Any suggestions?

UpstateNY · Post by **UpstateNY** » 29 Jan 2008, 13:28

I haven't received any replies to my inquiry so I thought I'd ask again. I've also used Ventil Saber (valve cleaner), higher octane fuel and Techron to clean the injectors. Still no luck - have got the "buck"- I'm stuck - oh darn!

Post by **jonesg** » 29 Jan 2008, 14:03

I had problems with my '90 740, from standing start it bucked until 2500rpm, then it would take off fine.

Turned out to be fuel pump.

I think the only approach is to sort out whether its fuel or ignition/elec first.
Can you test fuel pressure?
Does your car have a fuel pressure regulator? thats simple to test.

UpstateNY · Post by **UpstateNY** » 29 Jan 2008, 20:37

Thanks for your reply. I'm not sure how to test the fuel pressure, and I don't have any pressure gagues. But since it only happens at a certain rpm I agree that I'd better look more closely at the ignition. I bet I end up at the garage though.