2008 Avenger - Engine problem...maybe

[InkpenT]

Hi all,
Wondering if anyone can provide any insight. I recently purchased a 2008 Avenger 750. I know there was a previous problem with the engine, as the guy I bought it off had the engine repaired/rebuilt at a shop. I've had it in to the local Argo dealer for a full service check, and they say it's OK.

The issue I have is that there seems to be a miss in the engine when driving at higher speeds. Seems fine when idling. In neutral, the engine seems to run smooth until it's revved...then gets a rhythmic pulse to it. (Seems worse if the throttle is cranked quickly, as opposed to slowly building up.) When driving, it's OK at low speed but then seems to get the pulsing (missing?) when I pick up speed. Also seems to miss sometimes (low power), and then kick in. (A bit disconcerting when you're not expecting it in a narrow trail!)

I had a 650 Frontier previously, and engine ran smooth and steady all the time. So...wondering if this is at all normal for the Avenger? If not, any ideas on issue? Fuel system, EFI, engine?

[Mike]

That is not normal for an Avenger (or any machine). It seems like a fuel delivery issue. Start with the basics and make sure you have plenty of fuel. Make sure the fuel is good and not contaminated. Check your fuel lines to make sure they aren't collapsing on you. Is this a carbureted Kohler engine or fuel injected?

[msafi65]

Pull the connecters off at the ignition coils and verify they plug on tight. I've had several loose ones that loose one spark plug at times. The coils are below each end of the intake manifold. Also test fuel pressure if injected. Pressure below 35 pounds will cause problems.