Odd lack of power until 4.5K after idle (BAM converted mk2)

Hi there, I have a BAM converted mk2 running on the S3 management with standard ECU, DBW ect.

The problem I've got is a distinct lack of power after the car has idled for even a few seconds, it still pulls ok but not well until you reach about 4.5K (with foot to the floor) or until after about 5-8 seconds (normal driving) then normal power delivery is resumed. The engine pulls like it's meant to what ever the conditions unless you come to a stop and let it idle, then pull off again. Also the idle feels slightly rough once warm.

When stated from stone cold the problem isn't there until after a minute of two of driving.

The fault code i'm getting is 17963 - charge pressure upper limit exceeded

There are others codes are regarding the conversion such as, 18057-missing signal from ABS, 18058-missing signal from cluster, 17526-2nd lambda open circuit, 17931-missing signal from crash sensor.

The engine is relatively low mileage (70K), it has a brand new genuine turbo, golf rallye intercooler, ITG filter, forge 008, new n75, catch can set up, N249 bypass, I also skimmed the head and replaced the head gasket prior to fitting, it has brand new NGK plugs and it has a brand new MAF. The wiring conversion was done by Andy at ACR. The vendor that sold the engine to me said the car was not mapped and I have good reason to believe him.

What on earth could be causing this? Could the fact that cold start and just after seem to be fine point to something like the lambda? As if until slightly warm the ECU would be running from the base mapping, before switching to lambda feedback?

 

The new N75 valve isn't a N75J valve by chance?

 

The one I've got has part number 06A 906 283E, there seems to be a bit of talk around about this causing problems. I've have another in the garage that I think is an F so I'll give that a go shortly

 

I had a simular fault on my old Nissan Primera GT, it turned out to be dodgy aftermarket Lambda even though it was working sort of. After unplugging it the car run much better, so fitted a bosch one and hey presto sorted!!

 

Tried the 'F' suffix'd N75 and no change. Will try unplugging stuff next as Chrisrpal suggests. One thing i've just noticed that if I sit at idle and pump the brakes the idle drops further and hunts in time with the pedal going down. Another clue perhaps?

 

Yep i'd second that.

Especially the air lines underneath the inlet manifold.

 

i would also check your cam timing aswell

 

Is there a one way valve in the servo vacuum line?

 

Ah, cam timing would be a good one to check - cheers. Yes there is a one way valve, it's the mk2 one as it has a take off for the MFA, would the mk2 one take the boost ok? I'll check the vac hoses, timing and servo connection when it's daytime and hopefully not snowing.

Thanks for all the input so far

 

if cam timing was wrong I would expect to see some correlation errors and implausable or setpoint not reached type issues.
cars map std or remapped?

 

Faulty Boost pressure sensor?

 

I believe ecu is running on a standard map. Boost pressure sensor being the map sensor yes? Any way to check it? Still have been able to check the servo pipe etc due to the weather at the mo

 

My Mk2 is forever blowing the vacuum line off the back of the cluster, i've even tried zip tieing it on there. Going to need to get a proper clip or something now.

Worth checking, if you have a boost gauge, you should be seeing it @ idle at -1 bar if you don't have any vacuum leaks, if you have a small leak such as the vac pipe off the back of the cluster coming off, it'll float just above -1 bar. That alone on my 20v is enough to disrupt idle, intermittently it'll almost cut out with the rpm dropping right down then recovering last minute.

Ideally we could do with seeing some logs so it's easier to see what's actually going on.

 

-1 bar of vacuum? Seems a lot. Would have though 0.6 or so would be normal? Anyway the only vac gauge I've got reads in inHG's I got 16inHG which is about half a bar. Possible leakage then.

Still haven't checked the under the bonnet stuff lol

 

Re-did the servo line, cleaned the throttle body +alignment, now vac gauge reads a healthy 18.5 inHG's. car still does the very annoying holding back as described in the original post!

Which groups shall I log and post up?

 

002,020,031
003,020,115
002,115,118

 

v v v v New improved logs further down v v v v v

 

The actual boost v requested seems to go all over the place! Anyone know what's going on here?

 

What should i be investigating weekend. Map sensor, air leaks?

 

vac lines to the waste gate, etc mixed up.