Loss of boost - only in 3rd gear ??wtf??

[hooley]

All,

Got a 1.8tqs that boosts well in all gears except for 3rd.
Boost build nicely from 2000 to about 3500/3800rpm and then the boost drops off (like someone has thrown out an anchor) then picks up again.

Car is fine in 2nd, 4th and 5th....

Just put on a Forge 007p and this hasn't cured it.

Any ideas?
Wild stabs in the dark?

Cheers
Jas

 

[hooley]

Forgot to say - car is chipped and has had this problem for quite a while.
It is more noticeable when cold, and sometimes isn't a problem on part throttle, but is on full throttle.

J.

 

[Westy]

Do a search for MAF mate

 

[hooley]

I've read quite a lot on it, and tried running the car without it connected
Runs a little rougher and still has the boost issue.

Cheers
J

 

[Westy]

Ok that was just a starting point. HAve you got access to VAGCOM? If you do you could log your boost readings and see where its dropping.

Also have you checked your diaphram on the recirc valve and your boost pipes?

 

[hooley]

Brand new Forge 007p
Boost pipe were ok when last looked a few months ago...

But why only 3rd gear acceleration???

Jas

 

[Westy]

how long have you owned the car, has it always done this since you've had it? HAs it been mapped?

 

[hooley]

Owned 2.5 years
Chipped 18 months ago by Chipped-UK. No faults showing
Problem started about 6 months ago but only a problem on full throttle

I've got a vagcom cable from eBay and a shareware version of the rosstech software, but not sure I can scan with it. I can read faults and the only one showing is an oxygen sensor on the exhaust

Any more ideas anyone?
Cheers
Jas

 

[1animal1]

personally before doing anything id unplug the maf and see if it drives better....if this doesnt work reconnect then remove the DV (diverter valve), put your finger over the top hole and push the piston in from the bottom, press finger tight over top hole and if piston drops easily then the DV is at fault..... other than this its a general check of the pipes....you get maxboost in third in most cases so could be boost leak - failing all of the above it could be your coil packs missing, trouble you have then is changing all 4 or buying a new one and using the trial and error method.... there may be other things but these are what i would check first

 

[fran-s3]

Yes just to chip in on the above I think the main thing is to identiy if it's missfiring when u feel its not boostng... Best way to determine this as said is by hooking up VAG-COM and doing a run while in 3rd and looking at the missfire column. If my memory servers my correctly it's column 060 u need, but u may need to look that up first. If it is a missfire then as said coil pack, MAF or fuel pump in my case when mine was hesitating! Keep us posted.

Edit: Just spotted you've found you have a fault with your oxgen sensor, which is your lambda sensor! I'd def think this has something to do with it!!!!

 

[hooley]

DV brand new
Maf tested and car runs pretty much the same but less torque (it feels like it) and turbo feels like it kicks further up the rev range and does not pull as well
So I feel the maf 'might' be ruled out

What maf fits the 180 engine? Is it the same as the 1.8t non-quattro ( I know the S3 is a different size)

If anyone near the herts/beds/bucks borders fancyswapping maf's for 10 minutes (maybe also coilpacks, but these are also different on the cars

Mines a 2000 AJQ drive by wire 1.8 tqs

Cheers
Jas