Lumpy idle (very lean AFR) if pumping brake pedal

[Kaldek]

So here's a new one for you folks. Never really looked at my brakes much (as they just work) but in switching over to the Brembos yesterday and pumping the pedal for testing the brakes I noticed my AFRs going way lean and the idle going very lumpy.

If I press the brake pedal, the AFR is not affected. However, as I let off the pedal the AFR goes full lean momentarily and you can *just* detect the engine going lumpy for a second. If I rapidly pump the pedal it goes waaay lumpy and almost wants to stall.

So, normal behaviour, or dodgy booster valves? I was thinking perhaps the valve in the rear of the booster (which sucks in air from the footwell) might be sticky and hanging open when I let off the pedal. I've checked the one-way valve in the booster hose, it seems to be working fine.

 

[NuffNuff]

Air in the system or bad booster

Just to clarify mine idled weird pumping when I didn't have all the air out, full flush and bleed twice

In the morning your pedal will be all the way up and hard as on first application

The bleed takes a lot of fluid and heaps of air is in them. The pistons add a lot of air

 

[trotty]

Pumping pedal is using the vacuum in the manifold for the brake booster. I get it, I can make most cars idle funny when pumping brakes on the spot. It's normal/always thought it was normal is u are affecting the flow in the manifold.
Unless it's hissing or brakes are very hard when car is running I wouldn't worry bout it.

 

[Kaldek]

I can make most cars idle funny when pumping brakes on the spot. It's normal/always thought it was normal is u are affecting the flow in the manifold.
Unless it's hissing or brakes are very hard when car is running I wouldn't worry bout it.

I'd go and compare it to the behavior of our territory, but the Ford uses a MAP sensor for air metering which wouldn't be anywhere near as affected by such an air leak.