Odd engine braking question
 

So, sometimes when I pound it in 3rd or 4th and let it engine brake from 7k or so it feels weird. Like in the way it feels like it's not engine braking but then it will kick on and start engine braking. It's hard to explain. Basically it feels like I'm making no vacuum and then all of a sudden is does.

Thing is, I've logged my ECU and it is pulling normal vacuum according to the Haltech.

Any idea as to what it could be or am I just being paranoid and nothing is wrong?


It dosent' seem to act up in 2nd at all.

idle valve opens all the way and gets stuck?

No idle valve. Running a gotpsi? manifold w/ LS1 throttle. Idle is controlled with a hole in the plate. Could the spring on the plate perhaps be too soft and letting the plate open?

Yeah, letting it open, or it's hung up on something a little bit. There was a little valve thingy on NAs, but it slowed the plate down a very small amount before letting it close all the way. Basically to stop it from snapping shut completely.

Yeah this dosent have that. I remember that valve you're talking about. A few times also, under WOT in 2nd and off I KNOW the plate stays open for a hair of a second because the car keeps accelerating after i lift off the pedal.

Should I throw a stiffer spring on the throttle body then?

Definitely. Just throw a helper spring on there to make sure that's you're problem then make a more permenant solution. Look for a binding throttle cable or pedal.

For future reference, the device that slows the throttle plate on 1.6 cars is called a dashpot. It simply uses friction to accomplish its task.

Make sure your butterfly plate is not open perfectly parallel to the ground. I had a problem on my car where it was opening too far and for some reason, I guess the way air flows, it would not close immediately. I adjusted the stop just a touch and it's worked since.

Are you sure it's an LS1 throttle, and not a toyota throttle?