ABY engine cuts out when I floor-it. Overboost? HELP!

[tobodestroyer]

Hi,

My ABY S2 has started to cut out when I really push the throttle. The car accelerates like mad and then, at about 4k revs, it feels as though I've just slipped my foot off the throttle; the nose of the car dives as if the engine has stopped and then half a second later it's pulling like a train again. If I keep my foot down then it will do this two or three times in quick succession (over about 50yds). If I back off the throttle and keep the revs down then it's all totally fine.

Have I just described a turbo-boost problem? I'm still learning about how these turbo charged Audis work so please bear with me. The engine is usually very smooth but I have noticed a slight bit of lumpiness when driving round town within the speed limit. Could the two problems be connected?

My car has no turbo-boost guage, one of Paul's Homefries fitted and (apart from that) is in standard form. (I have noticed that the spring on the wastegate appears to be wound in quite a long way but I've been advised to leave that well alone).

Thanks for you help.

Tobo

[YELL MAN]

Could be a boost leak.

[newsh]

Yes, almost certainly a leaky hose.

[Al Wyn]

Would have said a hose Pete... still no boost gauge eh

[UrS4boy]

While it might be a boost leak, seeing as its mostly a stumble, I would suggest cranking the waste gate spring UP a few turns to see if the problem goes away.

When I installed my 1.9 Bar WG spring, I left the adjustment the same as I had my OE spring. That was too much (rate of boost rise was more than the ECU could handle and it caused a nasty nasty stumble if I floored it to WOT too quickly or for too long - it was fine if I just eased into it though).

[tobodestroyer]

While it might be a boost leak, seeing as its mostly a stumble, I would suggest cranking the waste gate spring UP a few turns to see if the problem goes away.

When I installed my 1.9 Bar WG spring, I left the adjustment the same as I had my OE spring. That was too much (rate of boost rise was more than the ECU could handle and it caused a nasty nasty stumble if I floored it to WOT too quickly or for too long - it was fine if I just eased into it though).

Thanks. I may give that a try as I have no idea what WG spring the car has been fitted with or how many turns of the thread have been added. As a guide, how much thread (if any) should be showing in standard fettle?

[ericd]

get vag-com or somebody with it and see what's been logged befor pulling the ecu fuses, obviously if it's easily repeatable it'll not be a problem...

[tobodestroyer]

OK. I've just VAG-COMmed my car and it came back with this;

VAG-COM Version: Release 311.2-N


Chassis Type: 8C - Audi 80 B4
Scan: 01,02,03,08,15,26

Address 01 -------------------------------------------------------
Controller: 895 907 551 A
Component: 2.2l R5 MOTR.RHV HS D02
Coding: PMC 1
3 Faults Found:
00281 - Vehicle Speed Sensor (G68)
03-00 - No Signal
00544 - Maximum Boost Pressure Exceeded
27-10 - Implausible Signal - Intermittent
00513 - Engine Speed Sensor (G28)
03-00 - No Signal
Readiness: N/A

Address 03 -------------------------------------------------------
Controller: 4A0 907 379
Component: Bremsen-Elektronik
Coding: 0265103050
Shop #: BB 23836
No fault code found.

Skipping Address 15-Airbags

End -------------------------------------------------------

Does this help me to diagnose the problem?

I've taken the bumper, aux-rad, intercooler and all hoses leading to the turbo off for further inspection. I see that the car still has the original O-ring on the Intercooler rather than that fancy blue hose. I've now got to replace all the rust cack round the bottom of the oil cooler too.

I'll replace the timing belt while I'm in there too.

[Jamo]

Inspecting the hoses wont cut it, you need to pressure test the boost system.

[tobodestroyer]

How do I get that sorted?

[Jamo]

I'm sure someone local to you on the forum will have a boost testing kit and help you out, basically you pressure the boost system with air and listen for leaks

[NEO]

And in combination to listening for them spraying all hoses with soapwater helps, then you get a visual clue to. And spray all areas where the hose connects to see if it leaks from the clamp.

[ericd]

If you're doing all the work you mention t/b etc, you may as well take all the hoses off and inspect them specifically around the marks left by the clamps on the hoses, flex them at the ends as thats the only way you might see a hairline cut on bl ack hoses, if you don't see any clamp marks them it probably wasn't tight enough, if you can replace some of the old/dubious clamps that would be a good time to do it , use the correct 6/7mm flexi shaft driver to tighten them all up , also with new clamps and refitting older ones, check them the next day (there's always 1 or 2 that seem to creep back on first fitting) and re-tighten them again.

most of us have seen the problems you described "fixed" by things as simple as retightening a loose clamp or completely refitting all hoses etc,etc,. The use of a pressure testing kit as suggested would be good, if you can get someone with a mityvac to check the small bore stuff as well

[NEO]

FInally found the problem on mine witht he same symptoms. Just thought I should link it in here if any one is digging in the archives. =)

http://www.s2forum.com/forum/showpost.php?p=428334&postcount=13