What is happening now??

I was driving on the highway doing a few consequent kick downs to check that when I depressed the gas pedal all the way down and press the switch, car would always down-shift. I did this a few times and noticed that if I am above 4000rpms and then press, the trany would sometimes decide not to downshift, even with pedal pushed all the way down. Perhaps that is normal

Now here is the thing: As I did that a few times, I noticed that the S/C shut down on two occasions as I pressed the pedal to accelerate. I know exactly how it feels as I had the I/C pump replaced 6 months ago and I know when S/C is not working.

Unlike with the classic faulty I/C pump behavior, the S/C came back on line quickly. At the end of my runs it was always on.

Is it normal for the S/C to shut down under certain conditions - likely too high AIT, despite of the working I/C pump ?

yes, it is normal if your IAT gets too high, it will shut down the supercharger...this can still happen even with a working I/C pump, especially on consecutive runs like you are describing with it being hot outside...

This just happened to me when playing with a new M5 (yeah would have killed me anyway) on the freeway Sunday. OMG, how depressing.. Luckily he probably didn't know as the traffic started getting heavier and we had to slow down anyway.

It wasn't that hot out 80-90 and was only driving for like 15 minutes or so. I was going around 80 and floored it and the engine roared but went no where. This is the first time the SC shut down since I have owned it. It was working again within a minute and hasn't given me a problem for the past 2-3 days. I went ahead and ordered a new IC pump anyway because it was replaced quite a while ago. Guess I will just replace it anyway since I am selling the car and don't want it to fail right after I sell it.. LOL..

OP - I've had something like this happen if I go WOT off the line - when it shifts from 1st to 2nd IIRC it just DROPs power/revs suddenly - it's back immediately once it shifts into 2nd. So if you're from a dig and running into it, maybe it's that (which is explained usually as hitting the rev limiter, but I've often wondered if it isn't IAT).

I've never had it happen at other speed/shift/rev bands, so if you're getting it going from 2nd to 3rd, or independent of shifts it might not apply.

I've seen several others report the power-dump I describe above.

Sorry if that just clouds this issue, but it's known effect.

That power dump on the 1-2 shift is generally the ECU backing off the torque during shift, due to lost traction. Try turning off the ESP and see what happens. Mine does a lot, when it is cool and I hit the throttle just right. It means the engine is producing a lot of power and ESP is overly aggressive.

if it's not the i/c pump then it could be the throttle position sensor. some people has problem with the throttle sensor which kills the signal...it would feel like you are pressing the throttle all the way, but the sensor is not sending full signal.

Yippie! I'm not the only one having issues with my S/C clutch not engaging.

Mine only does it from a stop...about 1 out of every 10 stops it won't engage. To get it working, I take my foot off the gas and re-apply pressure.

I've replaced the S/C and most of the sensors, but it still does it.

I'm guessing it is the sprint booster or TP sensor.

check your plug wires..

I had a problem with one of my Magnacor wires not making good contact and it was shutting down my kompressor.

I ran like that for about 2 months thinking it was my kompressor clutch.

The aftermarket wires are nice, but stock are better.

Thanks all for the feedback. A few things for me to consider:

* I had the whole S/C clutch replaced under warranty because of the bearing , so the harness may not have been connected well

* the throttle sensor was replaced a few months back and after that I changed the pedals with the nice aluminum set. I was careful with the harness, but who knows.

* I/C pump replaced a few months back, as I mentioned already

* no SB installed

Now that I think of what happened again, when the S/C did not work on accelleration, it seemed that it was back on as soon as I let off the gas pedal and keep cruising for a little while (can also tell by the sound). Though when I pushed the pedal again, I could feel the S/C going off - like something tripping the car and then the slow acceleration. All this at about 60 mph.

I really hope it was only the series of pedal flooring and rpm revs that caused all that.