98 AGU boost problems HELP!!

[Robbo1144]

Hi all,
Drove the girlfriends a3 today and noticed it was over boosting and felt like the car was lurching,
so i plugged into VCDS lite and did a few WOT logs. found quite a few strange things.....
heres one of the logs, it was a 2nd and 3rd gear WOT run

Another strange thing is it doesnt throw any fault codes, and i also unplugged the MAF sensor and it ran on the basic map, also checked all boost hoses etc for boost leaks, also checked the turbo because it was squealing its head off but it turns out it was cavitating because of the overboost.

the specs of the car are,
1.8t AGU 150
JBS k03 Manifold
k03
FMIC
Forge boost hoses
Forge DV007
Forge cold side reallocation kit
Miltec cat back


Any help would be gratefully appreciated,

Cheers,

Robbo

 

[Welly]

Knackered MAF dude by the looks of things.

AGU is absolutely reliant on airflow readings for calculating boost (in most instances) as it doesn't have a MAP sensor.

That MAF is under-reading quite substantially, you should be seeing 120 g/s on mass flow or so on a standard K03 150, with the mods you have should be a little more.

Start with changing that.

Also - all those mods and no map?

 

[Robbo1144]

Cheers for your help mate, thankfully got a spare one in the garage
hows things goin anyway dude?

Robbo

 

[Welly]

Good mate thanks, sling the spare MAF on and take it out. See what's what. Quick and easy test.

Unusual for a MAF to cause overboost.... But nothing surprises me.

 

[Robbo1144]

will do as soon as, gona be about a week until it actually arrives in germany. BFPO post is shockingly slow. i knew i should have flung it in the boot when i drove over last week.
Suppose its a "wait out until further info" lol
PS no map because shes skint!

Robbo

 

[Robbo1144]

Cheers for your help welly, i took the MAF off at work today and gave it a clean, car goes good now no overboost, or crazy cavitating noises.

still goin to fit the new one when it arrives anyway, i think the overboost was due to the ecu thinking it wasn't getting as much air as it actually was, so it was keeping the N75 from opening the waste gate and sending the fuel trims a bit low, so more air with less fuel= bag of s**te

Cheers,

Robbo