Strange boost problem.....

[JonathanS]

Hi Guys,

I was hoping that someone might be able to shed some light on a problem that I am having with my manual 2002 TT (non X50).....

I bought the car about 4 months ago and one of the wastegate actuator rods was corroded and not attached to the wastegate itself - at this point the car still went well and recorded 0.7 bar boost on max throttle. I have a workshop so repaired the wastegate rod and replaced the actuator rod nuts on both sides (trying to guess at the correct place to set them) I obviously did not set them right as the car then only recorded a maximum of 0.5 bar afterwards. I booked it in to my local Porsche dealer to carry out the major spark plug service and to set the wastegates correctly. So that was yesterday and I have been testing the car - now under WOT it shoots up to 1.1 bar then flutters down to about 0.5 then goes up and stays at 1.1 bar but to me if feels no quicker than when I first bought it (when it boosted to 0.7 bar) I am also worried that this is causing a problem elsewhere as the PSM and ABS failure lights come on and stay on till I turn the engine off now when I boost it hard - like up through the gears on a motorway at full throttle. Does anyone have any ideas? I have no knowledge of whether the car is 'chipped' or 'flashed' although it does have upgraded boost pipes and a titanium exhaust.... It has covered 54k miles. I am wondering if the dealer may have left a pipe loose around the DVs when they stripped the back end for the plug change (I have read elsewhere that leaks in this area can cause an overboost situation?) Or that it has had a badly flashed ECU due to the amount of boost that it is showing. If I am having these PSM and ABS lights come up is it most likely that I have now got a bust MAF - initially it took about 20 miles for the warning lights to come on but now it seems as soon as it is giving max boost up through the gears.

Please help!!

Many thanks

[wross996TT]

Boost issues in general could be:

1. Leaks (including DVs and WGs)

2. Plugs/coil packs

If you are getting ABS/PSM lights...first get the actual codes...those could signal several things...one of which is blown MAF.

If you are seeing 1.1 sustained, your ECU is flashed. I don't know what "upgraded boost pipes" are. Do you mean headers? Why are they touching the DVs for plug change?

[JonathanS]

I meant that the car has a set of silicon hoses running to and from the intercoolers - I was wondering if this had been done to help with extra boost from an ECU flash. I didnt think that the guys would go near the DVs for a plug change (I didnt when I did my own on my previous TT) but I was hoping it would just be a simple leak or something from there so I dont have to go and get my ECU flashed back to the standard state to get rid of this overly high boost and strange power delivery. Thanks for your suggestions, I will try and get codes read as soon as possible!

[JonathanS]

A little more information - today I plugged the car into my Snap On OBD11 scanner and the only fault code stored was P0234 - Turbo charger overboost. Does this mean that possibly my DVs are not functioning correctly??

Thanks again for any help!

[wross996TT]

P0234Boost Pressure Characteristic, Upper Value Exceeded

- Above Limit

Possible fault cause

♦ Leakage at pressure hoses from frequency valve to the bypass

flaps

♦ Frequency valve faulty

♦ Vacuum modulators for bypass flaps leaking

♦ Bypass flaps incorrectly adjusted

Silicon hoses are put on as a precaution due to more boost...they will not create overboost in any way.

[JonathanS]

Thanks - I realise that the silicone hoses are only usually put in as a precaution when raising the boost levels that is what led me to think that my car has been flashed at some point in the past. I think that I am going to get the DVs off the car and inspect them - they look like the originals anyway to I think that I will put some Agency Power or Forge items in their place. My wastegates have been correctly set this week at my local Porsche dealer and are functioning correctly from what they have said. I think that since they have set the WGs correctly the DVs can no longer handle the increased boost. I hope this is all it is anyway - the car does not feel that it is actually getting the extra power that 1.1bar of boost should provide, it actually feels slower than before....

Thanks again for your help.

[JonathanS]

I have fixed the problem... I decided to check over all the pipes around the DVs - they were all fine. I then thought I should look around the wastegates and their actuators (even though Porsche had just set them....) I found that the lovely Porsche Mechanic that had worked on my car had forgotten to re-attach the vacuum hose to one of the wastegate actuators!!!!! I havent paid them so yet so looking forward to what they have to say on Monday! The car now boosts to 0.6 bar (and holds it) with the odd peak of 0.7 bar so I guess all it correct and it is in the standard tune.

Thanks for your suggestions wross.

[wross996TT]

I have fixed the problem... I decided to check over all the pipes around the DVs - they were all fine. I then thought I should look around the wastegates and their actuators (even though Porsche had just set them....) I found that the lovely Porsche Mechanic that had worked on my car had forgotten to re-attach the vacuum hose to one of the wastegate actuators!!!!! I havent paid them so yet so looking forward to what they have to say on Monday! The car now boosts to 0.6 bar (and holds it) with the odd peak of 0.7 bar so I guess all it correct and it is in the standard tune.

Thanks for your suggestions wross.

No problem...glad you got it resolved...just because they are Porsche mechanics doesn't prevent them from making simple mistakes...LOL you just pay more for them.