S55 supercharged idle searching

[JonArkS55]

I have a problem in my S55
We have changed all sensors and timing chain and still with the same problem.
the car idle is searching all the time and the strange thing is that when pressing break pedal the idle come normal, when release brake the idle start searching again.
Any help pls?

 

[E55BOF]

Slight leak in a vacuum hose or connection somewhere, I'd say.

 

[JonArkS55]

Slight leak in a vacuum hose or connection somewhere, I'd say.

All vacuum pipes checked for leaking and connections checked. We are thinking throttle body maybe

 

[Bellow]

Fault in the brake servo? Disconnect the hose, block pipe and see of the variance with brake pedal application vanishes.

IAC valve more likely culprit than throttle body. Located on the throttle body it can be removed for cleaning. DO NOT physically alter the position of its plunger while removed.

 

[JonArkS55]

Fault in the brake servo? Disconnect the hose, block pipe and see of the variance with brake pedal application vanishes.

IAC valve more likely culprit than throttle body. Located on the throttle body it can be removed for cleaning. DO NOT physically alter the position of its plunger while removed.

I already disconnected the brake servo and the idle search still continued.

 

[Bellow]

I already disconnected the brake servo and the idle search still continued.

Did you do this...

when pressing break pedal the idle come normal, when release brake the idle start searching again.

.... with the servo disconnected and the engine side of the pipe blocked?

 

[JonArkS55]

Did you do this...

.... with the servo disconnected and the engine side of the pipe blocked?

Yes buddy

 

[Bellow]

The different behaviour with the brake pedal could be electrical ie, something is switched in or out when the brake is applied.
I'd take a look at the IAC valve next (given its job is to control idle speed) but if it is failing to react - what is it failing to react to ie, what additional loads are present that are identifiable?

My check for a functioning IAC valve is full steering lock and engaging drive (auto trans). If the idle doesn't falter with either of those loads being introduced then the IAC valve is doing its job. How does yours react to that?

If your engine is hunting without loads being applied (and AC switched off) it implies that something is forcing the hunting and the IAC valve isn't reacting in time. EVAP system? PCV valve? EGR system? Two of those are under electronic control and could be influenced by brake pedal position. Can you easily disconnect the brake pedal switch? Cruise control will also be disabled with the brake.

 

[JonArkS55]

The different behaviour with the brake pedal could be electrical ie, something is switched in or out when the brake is applied.
I'd take a look at the IAC valve next (given its job is to control idle speed) but if it is failing to react - what is it failing to react to ie, what additional loads are present that are identifiable?

My check for a functioning IAC valve is full steering lock and engaging drive (auto trans). If the idle doesn't falter with either of those loads being introduced then the IAC valve is doing its job. How does yours react to that?

If your engine is hunting without loads being applied (and AC switched off) it implies that something is forcing the hunting and the IAC valve isn't reacting in time. EVAP system? PCV valve? EGR system? Two of those are under electronic control and could be influenced by brake pedal position. Can you easily disconnect the brake pedal switch? Cruise control will also be disabled with the brake.

When the A/C and all kind of loads like lights etc are on it stills continue idle searching. Almost a year ago the engine started to do the idle search and when i take it for a long drive it will settle the idle but now unfortunately it is doing it all the time. No errors are showing on the star diagnosis the only thing is showing is on the computer when we press the brake the Idle speed detection comes on when we release the brake it comes off and this is a strange thing.
This is when i press brake it comes ON

This is when i dont press brake pedal it comes OFF

 

[Bellow]

when we press the brake the Idle speed detection comes on when we release the brake it comes off and this is a strange thing.
This is when i press brake it comes ON

This is when i dont press brake pedal it comes OFF

Suspect that is where the problem is but things like 'idle detection' are beyond my pay grade. You'll need better advice than I can give.

 

[Alps]

will be the little hose behind the rocker cover. common, normally pops off during rocker cover work of any kind

 

[JonArkS55]

Suspect that is where the problem is but things like 'idle detection' are beyond my pay grade. You'll need better advice than I can give.

I thankyou very much for your help

 

[JonArkS55]

will be the little hose behind the rocker cover. common, normally pops off during rocker cover work of any kind

Hi
Can you pls send me a pic where i can find the hose pipe pls?

 

[Alps]

Hi
Can you pls send me a pic where i can find the hose pipe pls?

if I recall its on the right hand side near the bulkhead side, in between surge tank and rocker cover. you may need to remove the surge tank to see it although it can be popped back in without. use a mirror to see.

bit tricky to get a picture... esp as I've sold the E55

 

[JonArkS55]

if I recall its on the right hand side near the bulkhead side, in between surge tank and rocker cover. you may need to remove the surge tank to see it although it can be popped back in without. use a mirror to see.

bit tricky to get a picture... esp as I've sold the E55

We have checked that as well buddy and everything seems to be ok.
We cannot find the problem