Air leak, any idea what this is?

[Rpmayne 0]

Hi, any idea what this is? Idle is rough especially cold, found the yellow bit in the middle of the picture sucking in air. If I block the holes up it improves the idle. Can’t see any other pipes disconnected. The open ends look clean as if something has fallen off. Cheers.

[Dox 23]

It’s the non return valve for the brake servo. If leaking it will affect fuel mixture and running / idling as well as servo brake performance 

[Cressa 44]

Definitely needs both ports blanking off. Its vacuum. Normally has a small plastic cap on each one

[Rpmayne 0]

Thanks for that, I’ll blank them off. Had it down the garage to bleed the brakes, may be they were left off. Cheers.

[Dox 23]

There’s no need to touch that vac pipe to bleed the brakes, that’s dry, takes vacuum from the running engine with the throttle closed to the servo. When the throttle opens the non return valve closes to maintain vacuum in the servo to assist brake pedal pressure, reducing effort on your leg / foot 

[Rpmayne 0]

Ok may be they both just fell off then, blanked them both off a now it idles, happy days. Cheers.

[Cressa 44]

1 hour ago, Rpmayne said:

Ok may be they both just fell off then, blanked them both off a now it idles, happy days. Cheers.

An easy fix is always nice 😊

[oneohtwo 8]

This is interesting. I too noticed these were exposed just after my rebuild but the engine ran fine. On enquiring on here and finding they are usually capped off I sealed them as I didn't have the caps. After I did this the engine ran horribly - idled OK but if I lifted off the throttle it would start hunting at idle and then stalling. I assumed the original caps weren't supposed to be air tight but were just to stop dust getting in so I unsealed them again until I got the caps. 

Everything has run fine in the meantime although I thought it odd that this was just unmetered air getting in, but ordered the caps anyway. Unfortunately ordered the wrong caps so still waiting for the right ones, but why would I be getting the opposite result of everyone else?

I am assuming it means something else isn't quite right, perhaps the throttle needs adjusting slightly for idle?

[Dox 23]

I'd be looking for another leak

[oneohtwo 8]

Took it into Stealth today for an ABS fault and mentioned this to Vince - he said it was most likely the ECU had adapted to the leak, and then when the holes were covered couldn't respond. They sealed them off and reset the ECU so hopefully that solves that one.

[Cressa 44]

Got to love an easy fix. At least it Is sorted

[oneohtwo 8]

Further update on that, picked the car up from Stealth on Sat - ABS pump all refurbed - but they also looked at this more and found the idle valve was sticking. The engine had been running fine with the pipe uncapped because that was the only way it was getting in air to idle. When they were capped off it was stalling and hunting when driving and coming to  a stop because the idle valve wasn't working properly. 

They got it off and cleaned it up with carb cleaner and some oil to free it up a bit and it has helped. On testing they found it stalled once but then was OK, and said it may still do this but to try and keep cleaning the valve. Since getting it back I have found it stalled a few times so this needs more work. Unfortunately it's obsolete from VW, hence why the didn't just replace and they've had mixed results with ebay specials. Will have a look to see if there are any new decent brands available. So not quite an easy fix, but at least I know what's going on now and can fix another gremlin!

[fla 9]

1 hour ago, oneohtwo said:

Further update on that, picked the car up from Stealth on Sat - ABS pump all refurbed - but they also looked at this more and found the idle valve was sticking. The engine had been running fine with the pipe uncapped because that was the only way it was getting in air to idle. When they were capped off it was stalling and hunting when driving and coming to  a stop because the idle valve wasn't working properly. 

They got it off and cleaned it up with carb cleaner and some oil to free it up a bit and it has helped. On testing they found it stalled once but then was OK, and said it may still do this but to try and keep cleaning the valve. Since getting it back I have found it stalled a few times so this needs more work. Unfortunately it's obsolete from VW, hence why the didn't just replace and they've had mixed results with ebay specials. Will have a look to see if there are any new decent brands available. So not quite an easy fix, but at least I know what's going on now and can fix another gremlin!

convert to obd2 and all the stalling issues disappear!  I do find its one of the best overall mods for a VR

[Dox 23]

29 minutes ago, fla said:

convert to obd2 and all the stalling issues disappear!  I do find its one of the best overall mods for a VR

Isn’t the idle valve built into the throttlebody on obd2?

[oneohtwo 8]

Ahhh yes! I would like to go OBD2. I had a thought to do it during the rebuild but then I thought changing/fixing too much at once would create more chance for things to go wrong. In hindsight that was probably the time to do it though. Although saying that with how rushed it was in the end, maybe it was best I didn't add too much more to the job list. Can't really do it now though... so will have to find a fix for the idle valve.

[fla 9]

5 hours ago, Dox said:

Isn’t the idle valve built into the throttlebody on obd2?

It is, yes. Its a motorised throttle body

[fla 9]

1 hour ago, oneohtwo said:

Ahhh yes! I would like to go OBD2. I had a thought to do it during the rebuild but then I thought changing/fixing too much at once would create more chance for things to go wrong. In hindsight that was probably the time to do it though. Although saying that with how rushed it was in the end, maybe it was best I didn't add too much more to the job list. Can't really do it now though... so will have to find a fix for the idle valve.

perhaps a plan for next year?

[1xshaunx1 27]

5 hours ago, fla said:

It is, yes. Its a motorised throttle body

And still available new

[Dox 23]

13 hours ago, 1xshaunx1 said:

And still available new

For how long? The last car vw fitted with a cable throttle must be nearly 20 years old?

 

I had a golf vr6 in 1999, 3 years old and 46k, the revs used to hang (fall too slowly between gear changes) on that one, took it to AmD in Oxford who ran a diagnostic and declared the tb may be faulty. I also had an Octavia 1.8t DBW that did similar (BAM engined tt is slightly better, but still hangs a little). I’d prefer the odd stall to laboured gear changes or faster changes that make you look like a novice driver.

I quite like the crudeness of OBD1 and cable throttles over DBW, maybe I’m just odd?

[1xshaunx1 27]

All electric motors will pack in at some point, which the obd2 tb incorporates, some call it a step motor. Some last a lot longer than others. I had a second hand one initially fitted which I found surged at 2k revs, a new VDO one cured that and gave 10 more bhp after fitting, before and after power run to see if any difference. 
My point is if you want it to run better obd2 will help same as the coil pack mod, can be done and fairly easy. 
If you are happy with a duff sunroof motor don’t fix or use that either.