IMRC open all speeds?

[ricky]

Hi 98 SHO stock, got the dreaded 1518 code this week and figured the IMRC finally had bit the dust despite regular intake cleaning. A visual inspection showed no frayed cables or broken gears. Start it, IMRC opens and stays open regardless of RPMs. Shut it off and it closes just as pretty as you please. Start it up again, it opens again, with about the same delay as the A/C kicking in when you first crank up. At present it poses no driveability problems except a little lack of low speed torque. Any ideas on cause and/or fix? Thanks for any help. By the way 1518 is the only code showing.

 

[SHOZ123]

Did you open the IRMC box? Mine did the same thing and the cable inside was frayed. This did not allow the wheel to completely retract and make the switch inside.

There should be more than normal slack at the butterfly actuator if this is the case. It's not a case of the butterflies actually being open but the cable does not retract enough.

 

[ricky]

yes I opened the box and saw nothing wrong, cable not frayed, pully good shape and gears intact. It acts as if the IMRC thinks the motor is at 3500k at idle. Does the IMRC get the signal to open from the PCM or just engine speed and opens accordingly? THANKS

 

[ricky]

Forgot to add to earlier post, I'm pretty sure the butterflys are opening after start and closing at shut down. I removed the appearance cover and observed both of the spring loaded levers [front & rear] opening and closing THANKS

 

[BodylessSHO]

Almost sounds like a PCM problem...Have you done anything to the car lately?

 

[SHOZ123]

Inside the IRMC there is a switch that sends 5V back to the PCM to show that the IRM is closed. When the cable is out the switch is opened.

When the PCM sees 5V all the time it thinks the IRM butterflies are closed all the time and you get code P1519. When the switch is open all the time the PCM thinks the butterflies are open and you get code P1518.

 

[ricky]

No, haven't done anything to the car. SHO is still stock except welded cams at 80k. Last thing done to it was oil change at 170k. Other than oil changes, I flushed the trans, spark plugs, and cleaned intake at 150k. PCM is giving the correct code because butterflys are open only closing at shut down. If it sounds like an IMRC problem I'll replace it. Other than the dealer, where can I get one? not interested in using any non SHO parts regardless of cost. THANKS as a shot in the dark [for me a least] could a bad TPS cause this?