Strange Boost Leak

[jonnaz]

have been having bad running issues with engine hunting ect performed a boost leak test from after the intercooler to stop any pressure leaking through the turbo oil seals. when pressurising the system air escapes from the throttle body via the rod for the butterfly showen in pic (quite big leak) also when the pressure exceeds 1 bar the TB stops leaking and injector #2 has a slight leak, i will change the o ring on the injector which should sort that.

Any ideas why it is leaking from the TB and how to fix it or is the TB shot?

[S2central.net]

Never seen that before, but then I would always bung at the TB hose - seeing as the butterfly valve and beyond is never going to be airtight as one or more valves will be open and the piston rings wont be airtight ==> you just end up pressurising the crank case.

Seems odd that you are getting air leaking from the TB shaft and that injector O-ring as I'd expect much more air to be escaping via less restricted routes.

[jonnaz]

pressure is escaping very slowly when above 1 bar i think only from the injector if there was an exhaust valve wide open it wouldnt pressurise. anyone know if there is a seal for the tb shaft?

[S2central.net]

I don't think there is a seal on the TB shaft... never had to pull one apart before - and they are stupid money from new.

[Rusty]

Problem with not testing the IM Paul is that you don't test the injector seals, N80 related pipes, or any of the small diameter pipes that feed off the head. Ideally use a compressor to get air in there quickly, it woun't hold pressure for long but you'll hear any leaks over the bnackground piston valve leak

[Thuppu]

have been having bad running issues with engine hunting ect performed a boost leak test from after the intercooler to stop any pressure leaking through the turbo oil seals. when pressurising the system air escapes from the throttle body via the rod for the butterfly showen in pic (quite big leak) also when the pressure exceeds 1 bar the TB stops leaking and injector #2 has a slight leak, i will change the o ring on the injector which should sort that.

Any ideas why it is leaking from the TB and how to fix it or is the TB shot?

Well, I have also a small leak from the throttle body axle on my AAN. But the engine runs fine nevertheless. So this kind of leak is not common?

[newsh]

TB shaft leak is normal as the shaft wears, my 3B leaks from there. Grease it up to slow the wear down.

[newsh]

I reckon you have a MAF connector or wiring problem. Also check the ground wires on the inlet manifold.

[jonnaz]

get code 533 adaption limit exceeded out of the ecu i have checked everything else and car runs really lumpy when maf is disconected. i have had the hunting problem for nearly a year doing my head in
The air flys out of the tb when pressure is below 1 bar and seals up when above 1 bar. should injectors hav no leak at all? the one i have is very small havent checked any other intectors as the inlet valves must only be open on cyl # 2.

[newsh]

Isn't it weird that its aok for a while after you unplug the MAF connector?

Read this. http://www.s2forum.com/forum/showthread.php?t=24544


Get a piece of really fine (1000 grit?) wet and dry paper and wear it out a bit. Pop the pins (one at a time) out of the MAF connector, you can do this with a bent piece of paper clip if you don't have the tool. Drag the wet and dry paper a few times through the connector pin. Wash with some contact cleaner. Refit.

[newsh]

Are you sure its the TB you can hear leaking and not the pipe just underneath it on the bottom of the inlet manifold? Very strange that it stops leaking above 1 Bar I guess if its like mine you can change the sound of the leak by wobbling the shaft..

[jonnaz]

i will give it a whirl tomorrow. i am guessing it ur taking the female pins out of the conector, and not the male pins out of the maf. yes it is fine after unplugging the maf and plugging it back in for a few minuets then goes back to hunting.

Thanks

[jonnaz]

yes opening and shutting the throttle changes the sound of the air escaping.

[newsh]

Yes, the pins out of the female connector. My theory is that there's quite a heavy current goes through the connector to clean the wire every time you start the car, this current puts a hot spot on the connector pin which affects the reading of the MAF. Wiggling the connector can put it right for a few minutes or days but eventually it comes back. My coupe would last up to a few months and run ok then suddenly be rubbish again, it would feel like it had a boost leak, the adaptation code would come up, sometimes it would do a boost cut, it would rev up suddenly as though the ISV was playing up, etc, etc... Since cleaning by the method above its been fine for a year or more.

Have you tried grabbing the shaft of the throttle butterfly and feeling for play up and down - side to side?

[jonnaz]

had the pins out of the maf connector rubbed them with wet n dry ect. car is still hunting at 1100 rpm it must be air entering of leaving the system. only does it when up to temp. there is ni play on the TB shaft.

im thinking about sending it somewhere to get sortd as i am getting sick any suggestions.


here is a link to the other thread relating to the surging of the car.

http://www.s2forum.com/forum/showthread.php?t=42003