Roush 427IR Idle issues

[169mph]

Originally Posted by twobjshelbys

This is a fuel injected 8-stack from Roush. I had the same engine. It's quite finicky.

After it warms up does the idle stay at 1150?

Do you have the dual fuel pumps? Have you checked pressure? I added a pressure gauge at the end of one of the fuel rails.

Thanks for the response.

It usually idles at 1050-1150 rpms. The rpms start dropping after it's been running for a few minutes. They'll drop until the engine almost stalls then they go back up normal for about 20 seconds and then the RPMs drop again. It's a cycle. Eventually the engine stalls. I keep the RPMs up when I go for drive but that gets old quick.

I have a Walbro 255 in-tank fuel pump, which I plan to switch to an aeromotive 340. I going to replace the fuel filter downstream of the pump when I switch fuel pumps.

I had issues with backfiring when decelerating in the past but after replacing the exhaust flange gaskets it rarely happens. Could an intake manifold vacuum leak cause the idle issues?