N54 Hissing at Idle - hiccup from full stop acceleration.

[matreyia]

There is a hissing sound...not there before at idle. Sounds like where the rear PCV area is located... when from a full stop, aggressive acceleration..the car will hiccup and then go right back to pulling strong as if nothing was wrong...but the more aggressive the pedal...the more strong the hiccup and will feel as if it will cut off the motor at some point.

My theory is the low side hose connection at the Valve Cover is leaking...and thus idle and low pressure driveability is affected. When pushing the pedal hard, the low side ceases to function and boost side takes over, but since there is a leak at the low side, the switch is being delayed to catch up with the abnormal vacuum state at idle RPMs.

Anyone ever had this happen?

I have lowside and highside catch cans and ports plugged.

 

[martymil]

Sounds like a vacuum leak, can be a little bitch to track down.

 

[matreyia]

Sounds like a vacuum leak, can be a little bitch to track down.

Yeah...and it's not the typical BMW B.S. "it's normal" either. It was not there before...DEFINITELY NOT THERE BEFORE.
I think its the hose connection at the plugged location that is getting too crispy so it's not sealing correctly. That hose came with the Radium Catch Can. I will replace this hose today with a more pliable one that can be properly sealed. Also, there is a potential that the RB PCV low side plug itself is leaking around the gasket and Valve Cover opening.

 

[fmorelli]

I had a heckuva time installing the RB PCV external valve on my setup. Two o-rings and one did not want to go - I think it was the inner o-ring on the RB. Given we were plugging ports, we didn't see a need for it and installed with just the outer o-ring and it worked great. If your stuff went in clean, great. If you had to fight anything, consider an unhappy o-ring. I agree this is not the typical BMW BS, but if I recall you recently made these changes so high degree of chance that the problem lies in most recent work/parts. Good luck!

Filippo

 

[matreyia]

I had a heckuva time installing the RB PCV external valve on my setup. Two o-rings and one did not want to go - I think it was the inner o-ring on the RB. Given we were plugging ports, we didn't see a need for it and installed with just the outer o-ring and it worked great. If your stuff went in clean, great. If you had to fight anything, consider an unhappy o-ring. I agree this is not the typical BMW BS, but if I recall you recently made these changes so high degree of chance that the problem lies in most recent work/parts. Good luck!

Filippo

I don't recall any problems with the RB adapter installation... I do feel physically that the hose connected to the adapter is way too hard and crispy to seal properly. There is a tiny give if you actually push and pull perpendicular to the adapter and valve cover hole/connection point, but that's probably normal and within nominal range...since the adapter itself does not have an actual thread that threads onto the connection hole. It just goes into the hole by lubing and pushing. Dependent on the rubber o rings to seal.

 

[matreyia]

I had a heckuva time installing the RB PCV external valve on my setup. Two o-rings and one did not want to go - I think it was the inner o-ring on the RB. Given we were plugging ports, we didn't see a need for it and installed with just the outer o-ring and it worked great. If your stuff went in clean, great. If you had to fight anything, consider an unhappy o-ring. I agree this is not the typical BMW BS, but if I recall you recently made these changes so high degree of chance that the problem lies in most recent work/parts. Good luck!

Filippo

Yeah, the RB adapter was installed long enough ago and it used to be connected to a Mishimoto Catch Can...then I got a Radium can and replaced the old hose with the one that came with the Radium can... BAD THING TO DO. The Radium hose is too hard from the start.

 

[NoQuarter]

For the large diameter hose, I had to switch to something much more flexible as well

 

[matreyia]

OK, found the culprit. After inspecting all hoses and connections and reconnecting them, and cleaning the RB Toyota adapter, I found two things...
1. the 90 degree connectors were backwards and not fully sealing. Fixed.
2. the cheap ebay oil catch can that replaced the Radium catch can had a design flaw that was in the form of a massive leak from one of the holes on the top of the can.

....AAAAND I just saw that I said, "right side" when pointing to the left side of the can... good lord. Just pretend that I don't speak good Engrish.

I plugged the leaky screw hole with a bolt I had in my scrap box and used teflon and thread sealant.
See photos and video link. All is quiet now. No more hissing sound at all.

 

[matreyia]

Ok... hissing is solve, but hesitation hiccup still persists... only hard acceleration after engine temps are reached. I suspect PCV Vent hose solenoid...the thing connected to the throttle body itself. Yes... I replaced the throttle body and it was not the problem. All hoses replaced, all connections and clamps replaced...