Octavia VRS hesitating on part throttle

[Saunders82]

Hello

I have had a on going problem with my VRS. It has 90k miles a stage 1 APR map and a ITG intake on it.

On full throttle the car is fine it pulls very well and is quick.

On part throttle/ normal driving there is always a hesitation like a flat spot when it comes on boost.This hesitation doesnt clear until you apply more throttle. It bogs down from 2500-4000 rpm

I car has no engine lights on.

I have replaced the temp sender,coils,spark plugs, Maf sensor, replaced the DV, replaced the N75 valve all made no real difference.

I have access to vag com but there is no codes against the engine control unit.

Any body have any ideas

[Neo_VR]

Have you cleaned the throttle body? (and then used VCDS to run adaptation on it)

 

this cured all my low RPM and part throttle issues.

[Saunders82]

Ill give it a shot

[Saunders82]

Ok did the throttle body clean and re adapt still the same

There is code now sprung up on vag com P1555 boost pressure upper limit exceeded

Any ideas where to look. The turbo has a very faint whine to it.

[Saunders82]

Any ideas anyone I'm still struggling on this :(

[f2evotomo]

N75 most likely, however I changed mine and it made a massive difference but now a couple of weeks down the line I'm getting problems again with boosting

[Saunders82]

Same as mine :( I put a new one on when it came up with the p1555 code but again part throttle it's not boosting correctly. I ran a data log on it and it's over boosting at part throttle. (Not by much 50-120 millibars) I'm going to try the n249 bypass next

[Bowders1]

I would get a boost leak test buddy.

Sent from my Samsung S3

[izard-industries]

Mine does the exact same thing! Mines all standard that I can tell of apart from a forge diverter valve. Mine seems worse when its cold, be good to know a cure for this!

[Bowders1]

Mine does the exact same thing! Mines all standard that I can tell of apart from a forge diverter valve. Mine seems worse when its cold, be good to know a cure for this!

 

I would first change your CTS (coolant Temp sensor) these can cause cold start issues and poor running until car warms up and even cause continuous poor low down running

[izard-industries]

Ok cheers will give that a go! Is this the one in the bottle? If that doesn't cure it what would be the next thing to try?

Cheers joe

[Bowders1]

Ok cheers will give that a go! Is this the one in the bottle? If that doesn't cure it what would be the next thing to try?

Cheers joe

Not sure what you mean, it is the one on gearbox side of cylinder head under engine cover. Sits in plastic coolant housing.

Sent from my Samsung S3

[izard-industries]

Ah I was thinking the one in the coolant bottle! I'll give that sensor you suggested a go and see what happens! Thanks

[Petelking]

Did you log the car?

How high are you boosting?

Log the car and see if your throttle is really opend all the way when you WOT.

Also check if you have any misfires or timing retardation when you WOT.

Edited 28 September, 2013 by Petelking

[Saunders82]

I ran the log on vcds

I ran throttle position engine speed boost pressure specified and actual and n75. At wot everything is fine after I put a brand new n75 on. I'll put a section of what I logged when the fault happens on here. I still think there is a small leak somewhere

[hazzard666]

had the same problem on my vrs, p1555 boost reached upper limit. found vacum hose from turbo to valve was split at the 90 degree bend were it attaches to valve. repaired the hose reset light and hey presto drives a treat, no flat spot/hesitation. hope this helps

[Petelking]

Yeah that would explian the cel but did you have the hesitation as well?

Op what are the block 32 numbers like?

Edited 30 September, 2013 by Petelking

[f2evotomo]

i'm still getting issues with mine, i'll have another check on vac hoses but what a knightmare this part throttle issue is.

[izard-industries]

I've just changed my coolant temp sensor. Definately seems better when car is warm still not 100% though! Think I'm going to have to get it into the local vw specialists and get them to to a boost system pressure test to see if there's any leaks!

Any other bits I could change?

[Saunders82]

Ok so I have left this for a couple of weeks as I was getting the car through its mot

So I am back on this again. P1555 has not appeared since I replaced the n75 valve. The group 032 log is

0.4% (add)

-9.7% (multi)

The second number seems low but I can't remember how those fuel trims work :( I've had to check numerous 2.0tfsi engines through work and we aim for 0% and 5%

Here is the boost logs for when it is doing the fault

Engine speed 3160

Throttle position 25.5%

Boost pressure specified 1180 millibar

Boost pressure actual 1390 millibar

At full throttle when it is not doing the fault I do have strange readings as well

Engine speed 3920

Throttle position 99.6%

Boost pressure specified 1740

Boost pressure actual 1910

Any help will be much appreciated