if i drive my car hard the boost wont hold all the time mainly in 3rd gear. it will boost to about 1.1 then drop off after about a second to 0.7ish and hold there but other times it will hold 1.1 til about 5000rpm is when it will start to gradually drop off. any ideas

thanks

Sounds like a boost leak. Can you hear and air leaks when the boost drops?

I think if you are going up hill it should hold boost longer? (might be talking ****e). You should see a peak figure, it will then drop slightly and should hold there, which is what you are describing. Fluctuation would be if it was 0.7, then at 1.1 then 0.7 again etc etc.

it happens totally random though say if i come off 1 island and boot it it will old around 1.1 come off the next n it just has no power what so ever could it be getting to hot i.e intercooler not working properly?

Your N75 solenoid valve controls the boost, so that really must be the first port of call.

I would also get a smoke test done to make sure you haven't got any boost leaks.

Steve

Is it remapped? Remapped stage 1 should be peaking about 1.3 and holding about 1.0 (depending on the mapper but that's the usual figures).

i always thought it was mapped but now im not so sure because mine peaks about 1.1 then drop off to about 0.7 but sometimes will not really drop of at all til about 5000 rpm

It sounds like a remapped one thats running badly, you wouldn't get a standard one peaking that high.

could be standard, just with a boost gauge that over reads?

its a bit more than that now i fitted my new fmic last night and now i have no boost at all it keeps poppin (excess fuel in the exhaust) and just generally runs like **** i have checked for leaks and found none (had a smoke test done) the pipes i have had to custom make myself 3" collar joined to a 2" pipe then a 2.5" collor to join to the pipes. is this going to small or could there be other problems.

Any fault codes with the over fueling? Do you have a blowing exhaust at all? How old is the pre cat lamda sensor?

its a bit more than that now i fitted my new fmic last night and now i have no boost at all it keeps poppin (excess fuel in the exhaust) and just generally runs like **** i have checked for leaks and found none (had a smoke test done) the pipes i have had to custom make myself 3" collar joined to a 2" pipe then a 2.5" collor to join to the pipes. is this going to small or could there be other problems.

Get Vag-Com on it at the very least you can do a fault code scan.

Or if you can, try and do some logging - actual vs requested boost (block 115), and log the timing and lambda values (blocks 020 and 032)

As Steevie said, check the exhaust. particularly the connection between manifold and turbo as if it's leaking badly there your turbo wont be spooling up and your lambda probe will be reading a mixture of fresh air and exhaust fumes which is probably why its overfuelling.

its had a decat done and both lambada sensors are back in the exhaust just no cat between them and do you think it is just coincidence then with me fitting my new fmic that this has got worse?

You need to get vagcom on it ASAP you have an issue det is bad !!!!

It could be a few things the only way to diagnose it is to do some logs.

Have you had it mapped for decat??

im going to get it plugged in tomorrow and no i wanted to get my intercooler fitted before i had it remapped. had my brother have a look tonight and he says it sounds like an air leak at the back of the engine somewhere.

Bet its leaking at the manifold. You didn't disturb anything back there when you fitted the intercooler pipework did you?

no my pipework is from the inlet to the cooler then from the cooler to the pancake pipe. just going down the garage now to see if i can find anything

Is it an FMIC? The pipework normally goes straight off of the turbo to the intercooler, then from the intercooler straight to the throttle body.

If the coolers got the inlet and outlet at the same end then you can keep the pancake pipe for the turbo to cooler part of the pipework

If it's an ebay special with the inlet and outlet at opposite ends then the turbo to cooler part of the pipework goes over the gearbox and the pancake pipe isn't needed any more.

both pipes are the same side so i have kept the pancake pipe ill take a picture of it tomorrow and upload it