So I took my car into the shop for the past 4 days and they replaced my faulty refurb MAF w/ Audi's newest revision, replaced a torn motor mount as well as my 02 sensors and checked my timing for me. Sadly all 4 days they had the car, it didnt do the whole cold start/first 5 seconds car is on boost drops from -15inHG to almost 0 and car acts like it wants to stall.

No codes on VAG, No CEL - wtf?

Here is Everything I have replaced so far: Coolant Temp Sensor from ECS, MAF, 02 Sensors, Hitachi "E" Coils, NGK Spark Plugs, Mobil 1 0w-40 Oil, Timing Belt/Tensioner and Water pump from ECS, New C.A.I. and Exhaust and new PVC valve.

What in the world could be causing this? I am 100% Stumped and so is the mechanic.

Is their and Air pump that comes on when you start the car for the first time that day? I notice on cold days I can hear, what sounds to be, an extra source of suction and after 20 seconds or so it turns off. I have a new OEM fuel filter i'll put on I suppose and run some Injector Cleaner through the system and see if that does anything at all...at this moment I don't know of anything else to check....No leaks anywhere, timing is right on the button.

Only on cold days it does this...[sm=dontgetit.gif]

 

I would check the EGR/Combi vavle. Make sure the vacuum line to it is still together and the air line to it are still intact also. Also follow the line across the front of the engine to check for crack/breaks in the line. This will be the air coming from the other line on your intake so make sure thats is intact aswell.

Combi valve is the silver circle under the compressor filter in the middle of the pic

 

Woot - I now have the culprit on tape and you can hear it Loud and clear.
Uploading now...

 

http://www.youtube.com/watch?v=3NJc5dphqE8

Here is the infamous "Pop" I keep suffering from. This is a LIGHT one - some times it will pop 4-8 times!

 

Hmm Cincy you may be right - I scope out the 2 easiest to see small diameter rubber hoses (The FPR one and the Valve you spoke of) Both look pretty badly weather checked and cracked. What role does that Combi Valve play in start ups/running?
Also I only saw 2 connections on the valve. One being a hard plastic tube (Im guessing this is the air line you speak of) and the other being the frayed rubber hose one. The one out of the FPR has a short distance of rubber to the bottom of the intake manifold. Thank god to whoever sent me that link to hose techniques and my silicone ones arrive monday.

 

just wondering.... how much did you pay with parts and labor to replace to 02 sensors

 

Definately change any/all vaccum lines if you can, then if you still have a problem see if you can check your upstream O2 sensor with a VAG COM and pull your oil cap and smell for gas, your injectors could be leaking into the cylinders causing it to flood and cause a hard start.

 

o2 Sensors cost me $245 w/ no labor to install. Not too bad of a price considering they were direct from Audi. I had considered the aftermarket ones that I would have needed to crimp on - But Ironically that's what the mechanic took out. Whoever crimped it/ Attempted to solder it failed. Water/dirt was in between the crimps and the sensor was shot. Soo out they came and in with the new!

 

Tech79 - It's interesting you mention the injectors since I took a rather in depth look at the yesterday. The majority of them have black (not oil) deposits around the sides of them (almost as if they're leaking) When I changed my oil as well, it had a strong scent of gas (Stronger then normal)

Are there any good Injectors that are match flowed for our cars out there that people are using? (At a reasonable price?) And definitley I will change vacuum lines tomorrow once the kit arrives. So far I only spotted the 2 Cincy informed me of - I'll check for more.

 

just replace all the vac/boost hoses you can. about 2-3 are attached to the underside of the intake manifold. and a lot of the ones on top of the valve cover......that sound is weird....i just started to hear a similar sound not as loud and only on cold starts....i just got my egr block off plate in and the resistor for no CELs so we will see what happens.....cant wait to get that pcv and egr crap out of there.