Turbo Lag - 2.0tfsi

[medvwb6]

Hi everyone, good afternoon.

I own a 56 plate b6 2.0tfsi with 78,000 miles on the clock, ive had the car remapped a while back and all was fine until the DV went, got that changed and all was good, about 2 weeks ago my dad had put diesel in the car and drove it for a mile or so.....had to call the right guys to come and pump the diesel out, the car was running extremely rough for a while but i filled up with Vpower and a few days later it was running back to normal, infact even smoother. (cambelt and water pump have already been changed)

Now i have noticed a lag in the turbo, that's what it feels like anyway. I have changed the N75 solenoid valve and that made an improvement but there is still the lag, what else can i do? I've taken the fault codes but left them at work but i do know one was "Boost control valve" which i think is P0239...the others are CAT Bank 1 below efficiency .

These codes were taken before i replaced the painful N75 valve, all hoses were fine.

The one thing i do notice, the harder i press the gas the less it seems to pull but if i find that spot and slowly push on the gas then the feel of a turbo is there and does pull you back a fair bit. But this aint all the time.

Could this have anything to with the throttle position?

Any help is much appreciated.

[martin1810]

You need a proper VCDS code read. The cat won't like the diesel but usually recovers ok. It really isn't worth guessing.

[medvwb6]

Hi Martin, thanks for your reply.

Ok, the codes taken are:

00665 - Boost Valve
01056 - CAT Bank 1 with P0420 below efficiency.

Another thing i noticed last night, strangly the car seems so much better when the engine is cold :S there is a lot more pull to it, whilst i never push the car when its cold i did try and there was a massive difference...

Its become that bad that a 1.8tdi 1 series bmw was going faster..........

Thanks in advance.

[martin1810]

The codes don't really help as I doubt you would spot a P0420 code from driving. That code means that the ecu is not happy when comparing pre and post catalyst lambda (oxygen) sensor readings.
It can be a failing catatlyst, faulty wiring or sensor, air leak etc. You may have to drive a bit more and then run another vcds fault read to see if anything else shows up.

[medvwb6]

hi again,

right, ive taken the engine cover off and checked for leaking hoses etc...couldn't find anything then i done the dipstick test, removed it and the car run rough! i heard a hissing noise and it turned out it had came from the PCV - crankcase vent valve.

i only had this changed about 2 months ago but it was a used one from a breakers because vw didnt have them in stock...

is there any other reason this would go again if i bought a new one?

also, does this PCV affect the MPG? myn has dropped dramatically.

[martin1810]

Any air that can "leak" in is unmetered air and it therefore effects the lambda readings which give information to the ecu about fuelling, so that screws up the fuelling and is going to affect the mpg.

[medvwb6]

ok, so it made no difference - i took it to a vw specialist and i was wrong when i said about putting the dipstick out....thinking the PCV is at fault.

they cannot find any problems with it, but the boost valve code 00665 wont clear, i have to book it in for a days investigation. Ive got a feeling this will become costly.

any further ideas what this could be?

[medvwb6]

sorry just to add, about 4 months ago i had the DV changed to the latest vw revison, could this have possibly gone or would i notice a more dramatic loss of power? would a carbon build up affect this?

[-M-]

If you have had the ecu remapped then anything on the boost side would be subjected to higher boost levels that the vw stock items could possibly take - stock VW DV only need a small split in the diaphram to cause power loss.

Have a look at www.awesome-gti.com.uk or www.forgemotorsport.co.uk - a bit costly but if you up the power from stock then other things need to be reinforced also.

[medvwb6]

Hi, thanks for your help.

The only reason i never mentioned the DV was because i had it changed a while back to this one:

http://www.awesome-gti.co.uk/product.php?xProd=13242

i thought as they said on the website that for chipped 2.0t this would be suitable.

Now, i will have a look tonight (weather permitted), remove the DV and find out if its split or not. The previous stock one split really bad.

Would this cause an engine warning light? as myn came on about 2 days ago.


Thanks again.