Rough Idle

My parents own a 96 3.8 Windstar and it has trouble codes P1537 and P1538. I know that these are for the IMRC's. I'm assuming the fact that the diaphram is not sealing correctly means that the IMRC's won't open at the upper RPM like they should. Seeing as the van rarely sees anything above 3500 rpm I assume that getting them repaired can be put on the backburner. However, the van has recently developed an irratic idle at approx.750 rpm and even died on me when I was changing from reverse into drive. Are the IMRC's causing this or is there something else going on?

The actuator diaphragm(s) may be broken, which would leak unmetered air into the engine .... which may be the cause of the rough idle.

Is that a repair that can be done here or would a dealer need to take care of it?

You should do some searchs on this forum. I have had no personal experience with the pneumatic actuators. From what I understand, the replacement actuators, bought new, are quite pricey.

But some poster has repaired them using his own techniques.

Those actuators are normally closed at idle. So if one is bad, it will probably cause enough vacuum loss for the other one to stay open which is why you are getting codes for both imrc's. I doubt both went bad at once. However you can check them (with the engine cold and off ) by pulling off the vacuum hose attached and to one and push the rod in. Then cover the vacuum hole on the actutator and release the rod. If it doesn't hold then that one is bad. If the first one holds then check the second. When you find the bad one, leave the vacuum line off and disconnect the actuator rod from the intake butterfly. Block the vacuum line with a screw or something and manually move the butterfly to the closed position. Now you should have enought vacuum for the good actuator to work (assuming one was good, if not disconnect both vaccum lines and block them and disconnect both rods and close both butterflys). Your idle should improve now as the van is running the way it should with the butterflys closed. Those butterflys open at 3000 rpm or so normally. Unless you constantly exceed 3000 rpms it is not a rush to replace the imrc, I have the same problem with my van and it is running fine with this temporary fix.

thanks for the help I figured out that it is the firewall side actuator. I called ford and they said it would cost $240, is there anyplace I could get a cheaper one?
2. When I plugged the leak and closed both banks the idle didn't improve it's still pretty choppy, but only at idle, no problems when driving. Any suggestions?

thanks for the help I figured out that it is the firewall side actuator. I called ford and they said it would cost $240, is there anyplace I could get a cheaper one?
2. When I plugged the leak and closed both banks the idle didn't improve it's still pretty choppy, but only at idle, no problems when driving. Any suggestions?

1.) Try www.y2kford.com/default.aspx?html=parts.html

Follow above link and order by part number.
They have the intake manifold runner control's (IMRC"S) for $143.40(each) plus shipping. Actuator parts are #F65Z-9S514-DA and #F65Z-9S514-CC.

I believe that the first part number is the firewall side actuator but check with them (or your local dealer) to be sure. Make sure you get some new bushings too (they hold the rod on the butterfly linkage), I don't have that part number handy but they shouldn't be more $7 or so at your local dealer.

2.) Are you sure you closed them? Both should be pushed towards the center of the engine to be closed. In other words push the front linkage towards the rear and the rear linkage towards the front. That's assuming you disconnected both actuators since you say you closed both. It's been awhile since I did mine but I'm pretty sure that that is the position for them to be closed. You could start the van and (carefully!) move them to what we assume to be the open position and the idle should get worse. If closing the butterflys doesn't complete fix your idle problems, then I would suggest changing the Idle Air Control Valve. It should run around $40 and is extremely easy to replace as it sits right on top of the engine manifold by the throttle body/air intake.

Yeah the right bank actuator is the faulty one, I placed a screw in the vacuum line of the faulty actuator and started up the engine, the left bank opened as it should. I then opened the other bank of IMRC's with the engine running and the idle didn't improve any. Thanks for the help I at least know what to replace once we decide to tackle the IMRC problem.

Is there anyway to be sure if it's the IAC. I removed it and looked to see if it was dirty or clogged, but I'm not sure how clean it should look. To me it looks like a normal amount of crud accumilation.

Yeah the right bank actuator is the faulty one, I placed a screw in the vacuum line of the faulty actuator and started up the engine, the left bank opened as it should. I then opened the other bank of IMRC's with the engine running and the idle didn't improve any. Thanks for the help I at least know what to replace once we decide to tackle the IMRC problem.

Is there anyway to be sure if it's the IAC. I removed it and looked to see if it was dirty or clogged, but I'm not sure how clean it should look. To me it looks like a normal amount of crud accumilation.


Cobra232, at idle both banks should be closed, not open. Was that a typo? They only open when you give a lot of gas (over 3000 rpm). If they are open still at idle then that is a problem. I'm not sure how to test the IAC, but other then the computer itself the IAC is the most responsible for idle speed.

sorry, yeah that was a typo. It just seems counter-intuitive to me the way they work, anyways I got everything sorted out

My 98 Widstar registers both codes - but I found a simple solution! I hope it works for you. I found that I could eliminate the Check Engine light by adding CHEVRON PRO-GUARD - it apparently frees up the sticky mechanical portion - the electronic controls work OK. Bought the 4-pack at Costco - under $10.00. Good luck.

I have the following OBD II CODES:
P1537, P1538, P0401, P0303
Found linkage to rear (bank 1?) IMRC disconnected. Reconnected but valve will only go to 1/2 closed position at idle and will not hold position when tested manually (push rod in and block vacuum inlet). (Front accuator seems to work ok).
The little plastic bushing that holds the rod in the linkage was $6.36 at the dealer....whata rip!
Could replacement of the IMRC this take care of the additional OBD codes as well? Idle is intermittently rough as well as under normal cruising speed.

BTW I tried the link to y2kford above but could not come up with these parts.

I have the following OBD II CODES:
P1537, P1538, P0401, P0303
Found linkage to rear (bank 1?) IMRC disconnected. Reconnected but valve will only go to 1/2 closed position at idle and will not hold position when tested manually (push rod in and block vacuum inlet). (Front accuator seems to work ok).
The little plastic bushing that holds the rod in the linkage was $6.36 at the dealer....whata rip!
Could replacement of the IMRC this take care of the additional OBD codes as well? Idle is intermittently rough as well as under normal cruising speed.

BTW I tried the link to y2kford above but could not come up with these parts.


PO303 is cylinder 3 misfire detected
PO401 is insufficient EGR flow detected

I think that these two problems are related, but I don't think fixing the IMRC's will help with these problems. You might have a bad EGR valve, and/or your EGR ports might be clogged.

As far as the IMRC's at y2kford try cutting and pasting the part numbers directly into the "search by part number" box... works for me.