Code 551, replaced IMRC and still no secondaries... suggestions?

[ACV1081]

Was getting code:
551 Problem in Intake Manifold Runner Control (IMRC) solenoid/circuit - Solenoids
on a friends 91 SHO and have since replaced the IMRC, but still have no secondaries. Rev the engine and they just don't react. I know he's losing lots of power because of this, but I don't know where to go next in terms of making them work again. The lines to and from the canister are fine and it seems they are just not getting vacuum. Any suggestions as to what could be causing this?

 

[projectSHO89]

Verify whether they open and close properly when the engine is first started and when the engine is shut off.

You can test the vacuum portion of the cicuit manually by rerouting the vacuum hoses to the intake port and bypassing the IMRC solenoid.

If the vacuum operation checks out and the 551 code still exists, verify the electrical connection to the solenoid. The red wire should be always hot with the ignition on. The other wire should also be hot except for when the solenoid is supposed to be energized. The PCM grounds that line to energize the solenoid.

Steve

 

[sdpatt]

Adam, recall that the secondaries are closed by vacuum and opened by releasing the vacuum and allowing the springs in the diaphragm actuators to extend the actuator's shaft. If they are not closing, then it is a lack of vacuum or power to the solenoid. If they are not opening, then the vacuum is not releasing (usually pinched hoses or high friction in the actuator/butterfly shaft mechanism).

 

[AutoSHO]

I believe that for the computer to throw a 551 code, it has to be an electrical problem. The computer otherwise cannot sense whether the butterflies are opening or not. I would say to look very closely at the wiring from the computer to the IMRC.

 

[Off Road SHO]

Adam,

Check to see if there is any water or corrosion in the connector on the IMRC itself and the junction connector at the back of the engine. After a thorough washing (boo hiss bad) water collects at the wiring harness connectors and if not displaced with WD-40 will corrode and cause high resistance and eventually open circuit.

Tom

 

[ACV1081]

Thanks!

Thanks for the responses everyone... I will be looking into the aforementioned suggestions as soon as he is over at my house again.

 

[RonPorter]

If the vacuum operation checks out and the 551 code still exists, verify the electrical connection to the solenoid. The red wire should be always hot with the ignition on. The other wire should also be hot except for when the solenoid is supposed to be energized. The PCM grounds that line to energize the solenoid.

Steve

I have also developed the same issue on my car. Tried three solenoids with no luck. Vacuum test works OK

Anyway, both sides hot? Seems that maybe the red side would be hot, and the other side open until the car is started to ground it and activate the solenoid to close the secondaries. Then at 4K, the ground would be disconnected to let them default to open again. Make sense, or no?

I had just tried throwing a meter plugged into the two female ends on the input wire, and I saw power when the car started. Haven't gone back to it since then.

 

[AutoSHO]

I believe both wires should be hot (12v) until 4k, and at that point one is grounded.

 

[RonPorter]

I believe both wires should be hot (12v) until 4k, and at that point one is grounded.

I'm not the electrical guru by any means, but it doesn't seem to make much sense that both would be hot. I wouldn't think a hot lead would be then grounded. Since the solenoid is not grounded to the engine (plastic part & clip), it would seem to make some sense that one side would be grounded upon startup to complete the circuit & activate the solenoid to allow vacuum to close the secondaries, then the ground would be disconnected at 4K to disable the solenoid and let them reopen.

Other sensors work this way, but I don't have a manual around to track this through. But then, stranger things have been designed!!

 

[AutoSHO]

I'll go examine mine tomorrow after I put it back together, and report what I find. My secondaries are definately working correctly.

 

[RonPorter]

Thanks. I'm a bit stumped on it, as we swapped solenoids with Fred Hurder's car at Lapeer a couple of weeks ago, to no avail. I then got another unit, which also didn't work. Can't believe that they are all bad!!

Also, does it specify 12v going to the solenoid? When I did my quick check with ameter the other day, it seemed to be in the 8-10 range (don't use the meter often, so I didn't verify...I was just looking for juice). That seems quite high for a sensor/solenoid being triggered by the pcm, but.......

 

[AutoSHO]

Have you tried swapping PCMs? Seems like it would have to be a computer issue if the solenoid is not bad.

 

[RonPorter]

No, I haven't. Don't have another X2J handy.

I also don't believe it's anything that serious, I still think it could be in the wiring......or maybe the solenoids aren't good.

Some background.......they quit working a few weeks ago, right after a clutch job. The nature of my driving right after the clutch job (20 easy miles around town, then a 1,000-mile trip) didn't show it up, plus the front idler (or maybe the alternator...will find out in a day or so) started whining on the trip, so I drove it easy, not knowing what the problem was. The bottom-end seemed soft. When we discovered the inop at the dragstrip, the solenoid had the clip broken off, so it looks like it hit something when the engine was free with the tranny out.

Could still be something in the wiring there, but it would be good to know what I should be seeing when I run a meter on the connectors when the car is off/on/revved past 4k.

 

[projectSHO89]

Could still be something in the wiring there, but it would be good to know what I should be seeing when I run a meter on the connectors when the car is off/on/revved past 4k.

Ron,

See my first response in this thread. The information you are looking for is already there.

The red wire is always hot with the ignition in RUN.

The other wire should read the same until the PCM electronically grounds that line. When it does so, current will flow through the solenoid coil and energize it.

Remember - when it's supposed to be de-energized, supply voltage on both leads. When the "low" side is grounded, you will have near 0 volts on that lead while still maintaining full supply voltage on the red lead.

Steve

 

[RonPorter]

Ron,

See my first response in this thread. The information you are looking for is already there.

The red wire is always hot with the ignition in RUN.

The other wire should read the same until the PCM electronically grounds that line. When it does so, current will flow through the solenoid coil and energize it.

Remember - when it's supposed to be de-energized, supply voltage on both leads. When the "low" side is grounded, you will have near 0 volts on that lead while still maintaining full supply voltage on the red lead.

Steve

Thanks, that does make more sense.

When I think of "grounding a hot lead", I think of standing in a puddle and sticking a finger into an outlet (!!!!). Killing the juice and grounding that side then seems reasonable. Just grounding one hot lead didn't make sense to me.

FWIW, what should the voltage be on either/both sides?

 

[AutoSHO]

OK, went out and tested my car, they work just a bit different than has been talked about here, but close.

KOER, idle: Red wire has about 13.xxvDC (my alternator is a little weak, but it was running the same voltage as the battery). Green/pink wire had about .8 vDC. Basically, the computer does not ground this wire, which means that no current can flow through the solenoid to engage it.

Wind it up to 4,000 and the computer grounds the green/pink wire. This results in 13.xx vDC on both wires (as measured against ground), meaning the solenoid is engaged and current is flowing through.

Thats how mine works, anyways. And thats probably the *only* part on my car that hasn't ever given me trouble.

Ron, is your car throwing the 551 code?

 

[Off Road SHO]

Ron,

Keep in mind that the little black cannister that is in between the plenum and the air solenoid is a one way valve with an air filter inside of it. It is important that the vacuum lines not be reversed on the filter cannister.

Some people think that the two "nubs" on the cannister face the firewall. They do not. They face the plenum and are used to lock the cannister in its' spring holder.

And BTW, if you shake the filter cannister a little and hear something rattling around inside, chances are the filter fabric retainer has come loose. This will allow unfiltered air into your plenum.

Tom

 

[RonPorter]

In the order of posts....

I have not had a CE light, and therefore have not checked for a code.

In tests of the vacuum circuit, we have tried connecting the feed lines directly to the manifold, as well as to three different vacuum cannisters, and all of these test were fine (secondaries closed as advertised), so (1) the vacuum lines are fine, and (2) the cannisters are fine (with no rattling).

From a pure function standpoint, the secondaries should work with the vacuum can out of the circuit (for test purposes), but that didn't work either.

Yep, this whole thing seems like a retty simple mechanism, and I've never had this issue over the years.

 

[projectSHO89]

Chris,

You have the function backwards.

With supply voltage on both terminals, there is no current flow through the coil so the solenoid is de-energized.

When the PCM grounds the "low" side of the coil, current flows through the coil and energizes the solenoid.

This is referred to "ground switching" as opposed to "hot switching" where one side of a coil is always grounded and power is applied to or removed from the "high" side of the coil.


Based on your test results, the solenoid is to be energized until 4k, allowing vacuum to pass to the IMRC vacuum motors and closing the secondaries.

At 4K, the solenoid is de-energized, vacuum is removed from the motors and they open.

The solenoid can be tested electrically by measuring coil resistance. It is likely between 50 and 100 ohms.

The vacuum portion can be tested with a short piece of vaccum line and your "personal facial vacuum pump". With the engine off, the solenoid should not pass vacuum. Start the engine, and it should. Monitor the solenoid "low" side to verify that the voltage is near 0 volts.

There is an internal monitor circuit in the PCM that detect the voltage level
of the output pin and is used to determine if the output pin has changed voltage levels when it was commanded to do so. It is this monitor ciruit that is used to determine whether a code 551 is to be posted.


Steve

 

[IAS92SHO]

One bank of my secondaries stopped working at 65,000 miles. I cleaned the intake and lubed all the moving parts, checked the vacuum, and it still did not work. I ended up playing around with nuts securing the secondaries to the intake and it end being the cause, or at least the solution. I loosened all the nuts, then retorqued them. If I over torqued any of the nuts by a few inch/# the secondary would not open.