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1998 Ford Windstar IMRC - how many?

03-23-2008, 10:29 AM
My mechanic has told me that I need to order two parts to fix the IMRC in my 1998 Ford Windstar. I understand there is a right and a left. Why are there 2 and what is the function of each? Originally he told me that I needed to replace the rear IMRC - is there such a thing as front and rear? That lead me to believe I needed only one part.

The symptom is that I smell exhaust fumes when opening the door of the car. How are these fumes a consequence of the IMRC?


03-23-2008, 11:25 AM
I do not see the connection between the IMRC and exhaust smell.

If the IMRC is not working, you should get a Check Engine Light (CEL) with a code stored indicating the problem.

Left, right, front and rear is confusing....
This is because the factory documentation calls the back side of the front wheel drive motor the "right" side.....and the front side of the motor the "left" side.....
This is a carryover from the rear wheel drive configuration.......the motor is turned sideways in the front wheel drive configuration.
The side of the motor with the drive belt....A/C, Water called the "front" of the motor.

The IMRC is vaccum driven on the 1996 through 1998 3.8L windstar.
They went to electrically driven starting in 1999.
I have a closeup picture of the right (rear) IMRC actuator and linkage to the shaft here

Both IMRC actuators share the same vaccum what usually happens is that one actuator develops a leak.....robbing both of them of the vaccum needed to operate.

The IMRC is in the OPEN position with the engine OFF....held there by springs.
When the engine is started.....and below a high level of RPM, the IMRC is in the CLOSED position, held there by the vaccum to the actuators.
So....they are easy to troubleshoot at idle.
With the engine at idle.....remove the vaccum line to 1 actuator and hold your finger over the end of the vaccum line.
The actuator that you unplugged should OPEN, and when you plug the end of the vaccum line with your finger, the other actuator should CLOSE.
If it does not.....then it is likely defective.

IF the connected actuator pulls in correctly....then reconnect the actuator and disconnect the other one......and repeat the test.
You should feel vaccum in the vaccum line at some point in this test.

The IMRC shafts pass through the lower intake shaft for each bank of cylinders.
This picture shows a closup of 1 of the butterflies.....

Each cylinder has 2 intake ports.
One port is open all the time......the port with the "butterfly" or plate on the shown in the open position...(engine OFF).
When the engine is running below 2900rpm, the shaft is rotated by the IMRC actuator to block the 2nd port.....when the engine rpm is above 2900, then the PCM sends a signal to a solenoid that blocks the vaccum to the IMRC actuators, and the shaft rotates to open the 2nd port...causing the engine to produce more power.

I did read something about a different RPM level for activation of the IMRC versus the 2900 that is for my '96.....being used on other years.
Also, I do not recommend racing the motor to try to activate them.......the closed with engine OFF and OPEN at idle is all you need to determine if the actuators are working.
Seems that the PCM activation and the solenoid are not high failure at all.

03-23-2008, 09:10 PM
Thanks, wiswind, for clearing the confusion on front, rear, right and left for the IMRC.

As the original owner of this Windstar, and having maintained it fairly well, I can say that it is a good time to be more educated if I intend to continue to maintain it from this point forward. As part of this education, I would like to know if the quote that the Ford dealer made to repair the IMRC is reasonable at a cost of $455. What am I getting for this? I was told that the parts can cost $300 apiece at full price and $200 at off-market and was told by different shops that I need one or two of these. I am assuming that the dealer is replacing one. What exactly is being replaced? Also, I feel that using the dealer is a better option since they seem to understand this van better than my mechanic, even if he claims he can save me on the parts.

The other main question I have is what is the symptom of the IMRC problem - is it loss of power? What happens if this is not repaired, since the van is running OK now? Why have two mechanics linked the exhaust smell with the IMRC?

I just had a tune-up and had to replace an MLP switch for a cost of $530, because the transmission was stuck in low gear, so I want to do the right research to determine my expected outlays to keep the van running well.

Thanks in advance for your help.

03-24-2008, 10:59 AM
I have read posts about a aftermarket IMRC actuator that did not work properly due to the electronic I would stick with Motorcraft.

If you have a CEL lit, you most likely will not pass emission testing, if they have it in your area.

Otherwise, it would not be good to have 1 side working and the other side that would have 3 cylinders operating under different conditions than the other 3.
Also, the vaccum leak could cause drivability issues....
These 2 factors could also seriously impact fuel economy.

Also, the most economical (fuel efficient) position for the IMRC is in the CLOSED position.....which requires the actuators to function.
One could fasten the IMRC closed....but you would still get a CEL for this as the PCM would not get a open reading when it was expecting it.
I am not sure if this would or would not impact the starting of the the IMRC is open when the engine is not running, and they close when they get vaccum.

One of the links that I provided shows the right (rear) actuator, this is what they would be replacing.
The actuator has a vaccum diaphram that pulls the shaft in toward the actuator when vaccum is applied.
The actuator also contains a resistor that tells the PCM what position the actuator is in.

05-26-2008, 03:19 PM
Thanks to the information in this forum, I did the IMRC work and am pleased that the engine is running a lot more smoothly now. Hard to believe I was running on only half the cylinders for a while...

In the same visit to the Ford mechanic, I also had the oil pan replaced since I was able to figure out that it must be the oil leaking onto a pipe that was causing all the fumes that I reported above. I figured this out after the problem got so bad that after only 4 miles of driving locally, I came home and actually saw smoke coming out of the hood! So the whole job did cost me, but now I have a running van that we were able to take on a 500 mile trip since the work was done.

One sidenote - the Ford mechanic wanted to replace a lot of gaskets and seals in order to fix the oil problem and this would have cost a lot more, especially in labor. I asked him to identify the 2 or 3 worst oil leaks and then he came back with a lower quote to replace the oil pan, which he claimed had rotted significantly. What are some of the other areas in the engine compartment that typically need replacement seals to stop oil leaks after driving for a number of miles?

Thanks for the great forums! :smile:

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