How to fix ZFR returning to idle stall or stumble

[08VRSS]

I wanted to share my findings for other cobalt owners who have this issue.

I haven't really touched my 26psi 93 octane tune in about 5 months now, I had this returning to idle stumble since i installed the ZFR about 20,000 miles ago. AFR would swing way rich when coming to idle sometimes and almost stall I'd say about 50% of the time. I played with everything imaginable in the tune to fix it. I came across an install instruction from borg warner and decided for kicks to read it, so this fix was completely by accident and is verified it works, not one hiccup 3 weeks later.

I had installed my ZFR with the BPV hooked up to the factory BPV solenoid just like the K04 was. DON'T DO THAT. Borg warner says to hook it up directly to a port on the intake. Mine is now "T"d off with alky injection on that port. So i tried it just to see how it would react. No more idle stumbles and the BPV is very very much more reactive, any throttle changes into vacuum and i mean any, it blows off. Car seems to drive much smoother between gears.

[hhrfreek]

Thanks good info...this made my day. I didn't have a idle stumble, but I could not get my zfr to spool quickly. I routed directly to the mani and it spools super fast now and blows off instantly like you say. The solenoid had to be controlling the vac pressure the valve sees so when spooling it was leaking for a short time because there was not enough boost behind it...Maybe tune related, but I maxed out every table I thought associated with it.

[ECaulk]

Interesting. I'm going to try this on my KO4+ just to see how it reacts, I get a odd return to idle once in awhile.