gotta 04 1.8T got a p0171 code i just changed the fuel filter had a valve cover gasket leak changed that. cleaned my MAF which is only 4 months old. all vac lines are good no leaks. i disconnected my MAF and the car ran the same just had the traction control light come on but thats normal. i dont have a vag-com can anyone help me.

 

just found a bad check valve the one that is on top the air box. it was sticking in the closed position major corrosion on the inside

 

You gotta becareful with them checkvalves, some people eliminates them and there's plenty of DIYs, but Audi put them there for a reason.

 

So did the bad check valve fix your lean problem? You could have another internal VAc leak that really can't be tested with traditional vac leak testing equiptment. You have to do the old pinch the hose off aft of the check valve to find out if a check valve is the problem.

Bad/dirty MAFs have been know to cause the car to run lean. The thing is, your throttle body is trimming out the long term trim most every time the car is under load in turn maxing it out and throwing the lean code. Internal vac leaks would likely affect idle performance being a dead give away. MAFs are a little slower to react. Have to you cleaned it?

 

what is the reason for all those check valves? can someone tell me

 

took the car to audi they didnt help for ****. told me o2 sensor and t.b. i gave it a shot still didnt fix it. got a 1800 rpm idle in park and it still misfires when stopped, in or out of gear doesnt matter. does anyone know bout cheaper ck valves i could find around town? audi wants $60 for each valve in anchorage.

 

My car set this code late last week, so i used a smoke tester onit and foundit to be a broken check valve.

I was at the dealership today, for the COP recall, and had them give me a quote on a check valve (the one to the right of the combi valve on the firewall) and they said that i couldn't get just the valve i had to get the hose that is attached to it.

I was quoted $255 for parts and labor to replace it. I think i am going to have to do it. Because after one of my coils going out today my cat is on it's way to an untimely death!

 

Do you think your could post a picture of where that valve was on your car? I've been checking for cracked valves all over the place and just can't find one. I would be greatly appreciative. I have had this problem for going on 6 months now and I am just really getting tired of it. I'm too stubborn to break down and take it to the dealer. Thanks.