[BMWM.D.]

Figured I’d post this as maybe it’ll help others out.

I haven’t been driving my ZL1 much these days due to other car projects, but last weekend I took a buddy out for a few hard pulls. I felt like the car was maybe down on power, but didn’t think too much of it. I chalked it up to good traction and/or PTM possibly pulling some midrange torque. This weekend I took it out some more and realized it wasn’t the tire smoking monster it usually is. It felt down on torque and was actually hooking from a 30 mph pull with TC turned off. Normally it’ll lose traction in 4th, sometimes 5th (A10 trans).

So now I’m concerned. I pull up the boost display on my P3 gauge, and it’s only making 6-7 psi through the midrange. It’s inconsistent, and sometimes will hit 10ish psi up top. Definitely not right, as it will usually make 12 psi peak, and have nearly full boost everywhere.

So I hook up my laptop and take some logs with HP Tuners. This was my first log since finishing my blower pulley tuning 2 years ago. In fact, I haven’t done any mechanical work on the car (other than oil changes) since then. Besides the boost curve, everything looked good on the log. Thought maybe I was getting throttle closures, but nope.

After swapping belts and chasing my tail a bit, I noticed the bypass valve being erratic while idling. It should be wide open at idle, but it was sort of moving around. After a little investigation, I found one of my crankcase vent lines was actually touching — and sometimes blocking — the vent on the bypass valve solenoid.

A quick reposition of the hose, and the car is back to trying to spin me off the road in 4th gear. Boost is back to 11-12 psi all throughout the rev range. I forgot how fast this thing was, and now I’m wondering how long this has been intermittently going on. None of these components have been messed with or changed from stock, so I feel like this is a pretty easy thing to happen.

Hope this helps someone, but I’m sure glad it was something simple.

[puppykat33]

can we get a pic or the line that was blocking the vent? or rather how it was sitting and how you repositioned it?

[BMWM.D.]

These aren’t my photos, but the vent I mentioned is covered by the foam I’ve circled. The hose that makes a 90 degree bend (seen in bottom pic) is the hose that was pushed up against the vent on my car. I just repositioned the hose in the plastic holder clips for now. I guess we’ll see if that keeps it away permanently.

[puppykat33]

thanks bud