IMRCs close before reaching 3000 RPM

[WINDED]

I have a 98 Windstar with 130000 miles. Recently I replaced the IMRC actuator nearest the radiator. Was getting p1537 and found the IMRC actuator would not hold under vacuum. Both actuators work as expected at startup, however after 12 minutes at idle the PCM seems to signal the solenoid to release the vacuum and cause the vehicle to lope or stall. I have timed this three times while either in park or sitting in drive with the parking brake on. Why would the PCM signal this if the vehicle hasnt reached 3000 RPM. I have had the codes pulled and get P1537,P1538 which makes sense if the solenoid is being deactivated. Just had it checked by the FORD dealer and they reprogrammed the PCM per a TSB. They said they couldnt find a problem, but I only discoverd the 12 minute rule after I got it back. My wife has a long wait in the school line to pickup my son and it happens there every time. Any insight would be greatly appreciated.

[busboy4]

Hi
recently replaced the control solenoid on my '96. On my van, per the EVTM manual, the solenoid should have battery voltage with the key in run. Therefore I believe the control solenoid opens allowing vacuum with power on, and the PCM shuts off power above 3000 RPM allowing the IMRC's to spring closed. That's all to say: I wonder if the solenoid is failing. If you could manage to "back probe" the power/gnd to the solenoid while the vehicle is running, and see whether or not you have power to the solenoid after the 12 min. point when your IMRC's open, you would know whether or not the PCM is commanding them open or whether the solenoid is "failing" closed in the presence of an open command i.e. voltage.

[wiswind]

OK....this is a long shot......
I am guessing that the combination of the vaccum being released and the stuck open codes are in opposition of what the PCM is looking for.
So, I am wondering about the vaccum source......and under the conditions you mention, the IMRC vaccum control solenoid.
The vaccum control solenoid for the IMRC is located on the back of the upper intake manifold.....passenger side.

I have read about a filter getting clogged in a vaccum control solenoid.
There is a little "cap" on the solenoid that has a felt filter inside.
I read that this cap can be removed, and the filter cleaned.
The filter becoming cogged can somehow cause the solenoid to malfunction.....the air filter is permitting a very small amount of air to flow in from the atmosphere....and somehow this small flow permits the solenoid to "breath".....and not get stuck.
I am just repeating what I have read....as I have been super lucky and not had an issue with my IMRC.

[Freakzilla69]

I'm just curious, I have a '98 too and I was wondering if the dealer told you what the TSB was for when they flashed your PCM.

I know mine hasn't been reprogrammed and I'm wondering if I should.

[WINDED]

Thanks BUSBOY4 and WISWIND for your input. I will try to check these ideas later today. However I am still curious about the fact that it takes exactly 12 minutes for this to occur and when I turn the key off and restart the van the system functions again until you reach 12 minutes and they release. I have tried tapping on the solenoid and it had no effect on the operation.

[WINDED]

Freakzilla69 I found the TSB listed on the web. I have the number at work and will post it here. It was supposed to be for rough idle and stalling.

[WINDED]

Freakzilla69 the TSB #5271 is the one. Here is a link to where I heard about it. http://autorepair.about.com/library/a/1i/bl785i.htm

[WINDED]

Well I took another look at the IMRC solenoid and monitored the leads coming from the PCM and at start up there is 12V to power the solenoid. This opens the vacuum line and actuates the actuators. After 12 minutes the solenoid is deactivated and the vacuum is removed. When this occurs there is no change in the voltage at the solenoid it continues to have 12V applied and the other lead continues to measure just over a meg ohm to ground. I also connected a current meter in the circuit and at 12 minutes the current died. When I cut the engine off and immediatelly restart the solenoid activates and it will take 12 minutes for it to deactivate. I have tried disconnecting the solenoid while the engine is running and reconnecting but this changes nothing it still wont work again until I restart the engine. I even connected the solenoid up to a 12V battery and it stayed activated for well over the 12 minutes. Should'nt the 12V potential at the solenoid change when the solenoid is deativated? I am at a loss now it seems to me to have to be the PCM. Any thoughts?

[busboy4]

I want to make sure I understand: at 12 min. is the 12v "signal" still there at the solenoid? If so, I would think the PCM is still sending an open signal to the IMRC's via the solenoid, but the solenoid is closing anyway - does that sound right? That would point to the solenoid would it not?

Thanks

[WINDED]

Yes. After 12 minutes the 12V is still there. However, it will not activate the solenoid. I can run the engine without the solenoid connected vacuum or power and after 12 minutes with 12V still at the connector I can reconnect the solenoid and it will not activate. Only after turning the key off and restarting the engine without delay will the solenoid again activate. This is only when the van is at idle not if you take off driving everything seems to operate without trouble only in extended idle situations does this rear its head. I cant believe it has anything to do with the solenoid unless it has a built in timer. I cant figure it out.

[wiswind]

OK.....I just double checked on the wiring diagram and descriptions on Alldata.
The IMRC vaccum control solenoid is ENERGIZED to have the IMRC runners CLOSED.
When the solenoid is de-energized, the runners are OPEN.....held open by springs.

To energize the solenoid......as with many items controlled by the PCM.....it is kind of backward from what most would expect......

The PCM provides the GROUND......not the +12V.
When the engine is turned ON......+12 volts is applied to one side of the solenoid.....and stays there.
The solenoid is energized by the PCM connecting the other side to ground.....providing a +12V drop across the solenoid......
+12V on the "hot" side, and near zero on the PCM side.

When the solenoid is DE-ENERGIZED by the PCM, the PCM opens the path to ground.....so you would see +12V on BOTH leads of the solenoid.

Once you verify the electrical state for the Solenoid, then you can know if the problem is the solenoid or not.

As another note.....since you know that it is working.......sometimes......try removing the vaccum line from the actuators....and spraying some seafoam or similar product down the line with the engine on......to draw it into and through the solenoid.....to clean it.
DO NOT USE CARB. Cleaner or similar product....as it is too strong.

As to why the PCM would stop providing the ground after 12 minutes.....I am at a loss.....as I do not know of any event in the PCM that is at 12 minutes.
I have a scangauge, and have checked.....even in cold weather.....the system goes into closed loop within a minute.....(Closed loop = using the upstream oxygen sensors).

[busboy4]

Hi

Good discussion Wiswind re:

>>>The PCM provides the GROUND......not the +12V.
When the engine is turned ON......+12 volts is applied to one side of the solenoid.....and stays there.
The solenoid is energized by the PCM connecting the other side to ground.....providing a +12V drop across the solenoid......
+12V on the "hot" side, and near zero on the PCM side.

When the solenoid is DE-ENERGIZED by the PCM, the PCM opens the path to ground.....so you would see +12V on BOTH leads of the solenoid.<<<

Based on my diagram I agree completely. The only ground available to the solenoid is via the PCM. However, stated a different way perhaps, would you then not read 12V "across" the solenoid when energized by the PCM (<3000) and 0V across the solenoid when de-energized? I believe yours and WINDED's discussion assume measuring each lead's voltage to chasis ground separately. I think measuring "across" the solenoid (by backprobing the leads, or directly if the connector is unplugged) will indicate its "commanded" state.

Forgive me if I am mis-understanding either of you Gentlemen. I am still wondering if there is 12V across the solenoid (i.e. solenoid circuit complete) at the time it re-opens (12min). If so, I do not think the PCM is commanding it closed, rather it is "failing closed".

On a different note: I am wondering where the PCM gets its RPM information relative to commanding the IMRC's open. I have a hunch that the throttle position sensor may play a key role i.e. throttle angle vs. RPM. With that said, could we be having a "soft failure" of TPS information? One would think that a CEL would be generated for TPS issues, but as we are scratching our heads....

Good discussion I'm learning a lot and hope for a resolution.

Thanks

[WINDED]

O.K. I have checked the the voltage across the leads and from each lead to chassis ground and this is what I have found. At starup there is 12 volts across the two leads if I remember correctly the red lead hot and the brown lead supplys the ground which measures around 1.5 meg ohms to chassis ground. The red lead has 12V to chassis ground and the brown lead has no voltage. After 12 minutes the red lead still has 12V and the brown lead has no voltage and reads 1.5 meg ohms to chassis ground. Also across the leads I still measure 12V. I have tried to measure voltage across the two leads with the solenoid in the circuit didnt have much success. I will try again to backbrobe as has been suggested. When I placed the current meter in the circuit the meter showed the current slowly decreasing over the 12 minute span then at 12 minutes it abruptly zeroed out. I dont have a copy of the wiring for this circuit is the PCM removing the ground or shunting the current away from the solenoid via a path of least resistance. I dont know if that makes any sense I am reaching. I do appreciate you guys sticking this out with me I know at this point some of what I am saying doesnt seem to make sense. I have electronics training but I will recheck my results and repost.

Thanks

p.s. What is "seafoam"?

[busboy4]

HI
thanks for the detailed response. First, seafoam is a fuel/intake additive that many have used to help "de-carbon" the intake system - most have used the pcv or brake vacuum line to "suck in" the seafoam liquid. You then let it sit, engine off for 5-10 minutes to soak, and then fire it back up and smoke the neighborhood I also have used it in a tank of gas for injector cleaning although I believe Berryman's Chemtool is more highly touted for that use.

To your solenoid. As Wiswind detailed, the circuit diagram ('96) shows 12V+ coming to the solenoid on the red line - hot when key in run. Then the brown line running to the PCM which provides ground. As he said, the PCM then must be providing "switched ground" if you will to control the solenoid. i.e. eliminate ground to de-power the solenoid, shut off vacuum and allow the IMRC's to spring to the open, high RPM position. As by your numbers, resistance to ground on the brown wire remained constant, even after 12 minutes, I believe you are still getting an "IMRC closed" signal from the PCM, as the brown wire should be "open, i.e. no ground" when the PCM signals the IMRC to the open position - high RPM. I can't really help but blame the solenoid in that situation as it seems to have a closed circuit (commanding vacuum on) yet opens anyway shutting off vacuum. I wonder if 12 min., while consistent is just arbitrarily the amount of time it takes for the solenoid to heat up enough to increase resistance to the point that there is no longer enough current flow to keep it open? Hopefully you will get some other opinions too. I know this stuff is frustrating.

[WINDED]

It is definitely the PCM deactivating the solenoid. I was able to rig up the meter across the solenoid in the circuit and at the 12 minute mark voltage ceased appearing across the solenoid. I also monitored voltage to chassis ground and had 12V at the red lead and the brown lead after the solenoid deactivated. In addition I monitored the resistance on the brown lead to ground and at startup it had approximately 1.2 M ohms and after the solenoid deactivated it showed over 20 M ohms. This is all taken with the solenoid in the circuit. Now why would the PCM be cutting off the solenoid at idle? I havent had the codes read since I got it back form the dealer but last time I did the only codes were p1537 and p1538. I am going to take it to Autozone and have them pull the codes today.