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IMRC Stuck

My IMRC valves in the intake manifold are stuck either open or closed. What is the effect on performance and should I have them repaired?

The effect of faulty IMRC valves is generally not that great although it would be my preference to have them working. These things alter the torque characteristics of the engine during acceleration.
It’s possible that computer codes could be present for this problem.

As to why they’re inoperative that will take some diagnosis as there are 2 of them and they’re controlled by the ECM through vacuum lines, solenoids, etc.

Are you assuming they are stuck because of a code? What is the code? What year is the truck?

The truck is a 2004 Ford F150, 5.4L, 3 valve. Do not know the code but dealer told me they were stuck in the closed position. I will get the code and post. Truck is as we speak pulling a trailer through the Rocky Mountains and the driver just called and said the engine seems weak. He is running out of overdrive at about 3200 rpm.

Well, you can’t “run out of” overdrive. Overdrive refers to a gear position. But it is right in that RPM range that the IMRC module is supposed to open the butterflies. So I’d say that the feeling of a lack of power could very well be from those being stuck closed.

It surely would help to know what the code is, but it is electronically operated so at the very least the driver could check to make sure that the wiring harness for it is intact.

If they are just gummed closed with carbon s/he could try a can of Seafoam into the engine’s intake.

Do you know what the dealer did other than pull the codes?

The other things to look at with the truck are the fuel pressure under load and to check it for any signs of an exhaust blockage, though loss of power can be related to any overdue maintenance items.

I called the dealer and they read code P2604. I do not know what this indicates?

I’m thinking that something just doesn’t add up.

There may be something I am missing, so take this as wide open to correction. But a P2604 indicates a problem in an intake air heater circuit…

and, intake air heaters are only used on diesels…

and I don’t think there is a Ford 5.4L diesel.

I suppose if this was the supercharged 5.4L, maybe supercharged engines use intake air heaters? But these are cold start items and I can tell you more for sure that P2604 doesn’t say a thing about the IMRC.