Rough idle and high fuel consumption

the intake rail is probably stuck shut due to a broken bushing on the rail control rods at the back of the intake

Hi Karl,

Just to confirm what is happening, you were told that you have a cylinder three misfire, so you replaced the injector and now you have rough idle and high fuel consumption? Or you have had rough idle and high fuel consumption the entire time, you were then told you have a cylinder three misfire and still rough idle and high fuel consumption?

I suspect you replaced the injector to address this, and it did not make a difference. So, if that is the case, we need to start with running through this guide and see what we can turn up:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

If we have spark, fuel is most likely ok due to a new injector, but we should check the spray pattern of the injector or use a test light to make sure it is firing. Lastly check the compression and rule out mechanical issues on this cylinder.

https://www.2carpros.com/articles/how-to-test-engine-compression

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

If this all checks out, then I suspect Damon is correct that this could be the manifold tuning valve issue.

It is odd that it would cause just an issue on one cylinder, but it is possible.

So, I am attaching the info below on this for us to test. Basically, these shutter should be closed until the engine reaches 2,600 RPM.s

So, let's run through this and see what we can turn up.