Power loss above 4,000 RPMs? Check your IMRC!

[skater]

If you are experiencing a loss of power between 4,000 and 5,000 RPMs and have the 2.5L Duratec V6 engine, you may have a problem with your IMRC.

If you've been linked to this thread, please read it and try the diagnosis steps below. We have hundreds, possibly thousands, of threads where people have had this problem, and we're tired of explaining it every time. It's nothing personal.

What is it, and where is it?: The IMRC (Intake Manifold Runner Control) is a box that is mounted just underneath the plastic "2.5L Duratec" cover in your engine bay. It's purpose is to open the secondary air intakes, which are controlled by butterfly valves in the lower intake manifold. The IMRC has a long cable coming out the right side that loops under the intake and connects directly to the rear bank of butterfly valves, and a linkage from there connects to the front butterfly valves.

Failure Modes: It is common for these to fail. In particular, they frequently will work fine when cool but then fail once the engine gets hot. Usually they fail to OPEN the butterfly valves, which means that your engine will choke around 4,000 RPMs or so because it's not getting enough air. Sometimes they fail to CLOSE which means your engine will run poorly under about 3000 RPMs.

Occasionally the linkage between the two sets of valves will become disconnected, so the IMRC is working but is only opening the rear bank of valves.

Diagnosis steps:
1. Pop the hood and start the engine when it's cool. Watch under the throttle body and rev the engine. Around 3,400 RPMs (it varies), you should see the linkages moving that are opening the butterfly valves for the secondary air intakes.

If you see the front bank of valves open (i.e., closer to the front of the car), then both are opening. If you don't see the front bank opening, watch the rear set to see if it's working. If it is, then your problem is that the linkage is disconnected - the IMRC is fine. Reconnect the linkage and you should be good to go.

2. Drive around and get the engine nice and hot, then try it again. You should see the same thing. If it's not moving, your IMRC is failing.

3. If you are having an intermittent problem, you can also disconnect the electrical connector on the IMRC (you have to remove the plastic Duratec cover to do so) and drive around and see if that's what your intermittent problem feels like. Note this is likely to throw a Check Engine code.

4. Of course, the IMRC isn't the source of every problem. If the IMRC is working correctly and the problem is different than what you felt when you drove it in step 3, please post (in another thread, not this one; if you've already started a thread, please continue that one) and let us know that you've tried these steps and that isn't the problem.

Repair/Replacement:
1. The best thing to do is simply replace the unit. You can find used ones fairly cheaply, or you can buy a new one from a Ford dealer. Try calling TeamFord. I think, though I haven't priced one, they run about $200.

2. You can replace the transistor in them. This has had mixed success. I don't know if it really works or not. See here.

3. Cleaning them: Some people have had luck using electric motor spray to clean them. I think this is a temporary solution, usually.

4. Some people have relocated their IMRC. Others feel this is ghetto. See here for one thread, and here's a thread on CEG about it.

5. Less drastic than the relocation is to simply remove the plastic Duratec cover that probably traps some heat inside. The cover is cosmetic only, so you don't lose anything mechanically.

Steps to Replace It:
1. Unplug the electrical connector.
2. Remove the bolts holding it in place.
3. Disconnect the cable. You have to squeeze the end together and push it through. It's under the throttle body, so you may want to take off the intake to have more room to work.
4. Remove the old unit/cable, being careful to note the routing of the cable.
5. Put the new unit in, following the same routing.
6. Connect the cable, bolt box down, connect the electrical connector, and test it.

Please send any corrections/clarifications/updates to me. Thanks!