# Audi A3 1.8T AUM, feels very weak/sluggish and backfires on start up



## VWF Clay (Aug 11, 2006)

My 2002 Audi A3 1.8T AUM has been out of action for a while, I blew the head gasket a while ago so it went in to a mate workshop to get that sorted out and gave it a service, cambelt, waterpump, thermostat oil change and been replacing any water/boost/vacuum hoses that were worn or looked a bit dodgy. 
While the head was off I had some mild Billet Performance Cams fitted, 247 / 252 degree with 8,8mm / 9,5mm lift.

The car is all back together now, but if you turn the key and hold it there’s a loud backfire out the exhaust. But if you turn the key and then quickly turn it off and try again, then it starts fine. 
My mate then asked me to come take it for a test drive because he thought it was a flat. So I took it for a drive last week. The car is drivable, it goes and does rev up, but slowly, and didn’t feel right, it does seem a bit sluggish and didn’t always feel like smooth power, almost a bit of hesitation or surging at times. Yeah it just feels very flat and underpowered!

I then got the diagnostic contraption plugged in and found these two fault codes: 

16725 
P0341 Camshaft position sensor (A) circuit bank 1:range performance 

And 

17705 
P1297 Connection turbocharger to throttle valve: pressure dropped 

Have any of you chaps experienced this and have any ideas what could be wrong? 

Quite a few people have said the timing is probably out or it's a tooth out on the cambelt or chain. 
So my mate took the tappet cover off and double checked it again and he says it looks right? But I think I’m going to get it double checked again. 

I have been driving the car to work this week hoping the problem would clear, but it’s still the same, very weak! 

Have any of you chaps seen or heard of this sort of thing happening??? 
And do you perhaps have any ideas or suggestions...??? 

We really don't know what to try now??? 

Thanks


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