rivverat

1996 Ford Windstar 3.8 L 92K miles one owner.
P1538 IMRC stuck open, (Bank 2). That is the only code I get, no others. Both IMRC’s SEEM to be operating properly. The van runs fine, no roughness and does not hesitate or die.

I have verified:
-there are no holes in the actuator diaphragms, that is they both hold vacuum
-the butterfly rods move freely and smooth as silk
-I replaced the little plastic linkage retainers
-operated both IMRC’s manually and by removing the vacuum hoses
-ran engine up over 2950 rpms and verified both actuator do in fact close and then open after rpms drop.
-cleared the code (and CEL) by removing the negative battery cable.

The light came back on after driving about 20 minutes. I pulled over and raised the hood and checked both IMRC’s again, they were open when idling, closed when I pulled the vacuum line which is correct.
So… I’m thinking that the IMRC SENSOR may be bad. It is integral with the IMRC. The wires that plug into them are a 3-wire plug. I have tried to test them with continuity and ohms but really do not know the proper procedure.
The readings I do get seem to be consistent between the 2 IMRC’s though.

Does anyone know if there is a procedure to check the sensors?

Does anyone know if I should be looking elsewhere?

rivverat

Ok, for anyone that is interested, I had time to look further into this weekend, here's what I found:
I re-checked what I had previously verified, that is, that the actuators did in fact open and close when they should, and that the linkage and such was not in any kind of bind. I also went to the library and got a hold of an engine wiring diagram that shows the IMRC sensor circuits.
I cleared the P1538 code and then I swapped the plugs around, that is I put the plug from bank 1 on the bank 2 actuator and vice versa. Then I drove the van to run some errands. The check engine light came back on after some drive time so I went to AutoZone to have the code read. Guess what?
It was a P1537 (which is Intake Manifold Runner Control Stuck Open (BANK 1). (BTW, IF you have AutoZone or someone else read your error code be sure to get the alphanumeric code and not the description for them, different code checkers have different descriptions, and they wanted to sell me a new Idle Air Control, which was not the problem.)
Went back to the house and got out my meter, unplugged the electric plug for the sensors, and read resistance across the sensor terminals. Bank 2 sensor did not have the same readings as bank 1. So I feel 99% sure that both IMRC's work mechanically correctly, its just that bank 2 sensor is cooked and tells the computer there is a problem. So now I get to try and find a cheap IMRC for bank 2.
Hope this helps some one else.

clocker

This was an excellent post. Thanks so much for the help.
Ian

k8e

I am having the same problem with a 98 Windstar (i.e. P1538 code) and was wondering if you could tell me how changing the IMRC worked out for you and about how much the repair costs. I received the DTC at the county emissions testing center, so is that a more reliable reading the an Autozone reading (I've gotten the same Idle Air Control code before too)?

Thanks.