Time to troubleshoot a hiss (possibly EGR related).
Posted: May 1st, 2009, 12:57 am
This started happening after ZE went in, with headers, high flow cat (meow), etc.
Been like this for a couple of years now, but I was always too busy with other parts of the car to sort this out.
Anyway, what happens is if I rev the car and then lift off the throttle, as the RPM drops, there's a continuous hissing sound coming from what seems to be back side of the motor, exhaust area... This hiss also corresponds with certain hindrance in performance. Specifically, at WOT as the car is under load, I can hear it a little bit, but it is most severe when I lift off the throttle in higher RPMs, and as it hisses I experience some major engine breaking.
Now, I don't know how much engine breaking ZEs with a stock flywheel do at higher RPMs, but it seems I get a bit too much.
It goes like this.
1. In gear, rev to say 4K or 5K - no hiss unless WOT
2. Lift off the gas completely, still in gear - for a moment there's complete silence and no engine breaking
3. After a moment of silence - very loud hissing (think turbo blow-off, only continuous) and the car bucks forward pretty severely, as if I dropped the clutch, and then massive engine breaking as car rapidly decelerates
I don't experience this when I'm cruising slightly on the gas, but if I lift, I hear it.
Somehow I feel this might be EGR related or something of the sort, because I'm not sure what else it could be. I checked all my vacuum lines and connecitons, and found no leaks.
Been like this for a couple of years now, but I was always too busy with other parts of the car to sort this out.
Anyway, what happens is if I rev the car and then lift off the throttle, as the RPM drops, there's a continuous hissing sound coming from what seems to be back side of the motor, exhaust area... This hiss also corresponds with certain hindrance in performance. Specifically, at WOT as the car is under load, I can hear it a little bit, but it is most severe when I lift off the throttle in higher RPMs, and as it hisses I experience some major engine breaking.
Now, I don't know how much engine breaking ZEs with a stock flywheel do at higher RPMs, but it seems I get a bit too much.
It goes like this.
1. In gear, rev to say 4K or 5K - no hiss unless WOT
2. Lift off the gas completely, still in gear - for a moment there's complete silence and no engine breaking
3. After a moment of silence - very loud hissing (think turbo blow-off, only continuous) and the car bucks forward pretty severely, as if I dropped the clutch, and then massive engine breaking as car rapidly decelerates
I don't experience this when I'm cruising slightly on the gas, but if I lift, I hear it.
Somehow I feel this might be EGR related or something of the sort, because I'm not sure what else it could be. I checked all my vacuum lines and connecitons, and found no leaks.