mmasire88

I have 04 1.8T that would appear to have a very hard to track down vacuum leak. Basically, it starts up and idles around 1200~ when cold. about a minute later it will drop down to 800~ and thats where the fun begins. I'm getting a mis on cylinders 1, and 2. I replaced both coils with genuine vw/audi as well as all 4 spark plugs. I also replaced the maf. I'v cleaned the throttle body, replaced the y-fitting mounted on the back of the valve cover. I have removed the crank case breather hose, and check valce(which appears to be working correctly, but to no avail nothing has helped/worsened/fixed the issue at all. I will add that there is a very loud hissing noise, which sounds like it's coming from inside the intake manifold. It's not coming from below it, or behind it. My question is, what could be causing a misfire on only cylinders 1, and 2? Possibly the intake manifold gasket, or head gasket? There's no difference at all in the way the car runs, when the maf is plugged in or not either, not sure if that has anything to do with anything, but I figured I would add it in. Thanks in advanced for any help guys!

naconi

Not sure what you mean by this part "I have removed the crank case breather hose, and check valve" but the breather assy on the 1.8T goes from the oil filter assy through a t-valve that goes through the PCV up to the intake, the other part of the t-valve goes up to the PRV. All the plastic parts involved in that get brittle and break. Since it runs under the intake that could be the noise you are hearing.

http://www.audizine.com/forum/showth...rittle-Crumbly)

mmasire88

Sorry I guess I should clarify. My breather hose, comes off the crank case, curves up into a T, which has a check valve built into the T. Iv been making my runs throughout the vacuum system. Check for,cracks or old brittle lines, bad check valves etc. I had replaced the breather hose, because upon trying to remove it from the crank case it completely shattered. But aside from that it was fine, and the check valve was working. The loud hissing noise I'm hearing is definitely coming from inside the intake manifold, I have an 01 a4, also an 05 a4. And neither of them have any sort of noise coming from the intake manifold. I'm getting misfires that seem to be completely restricted to cylinders 1-2 that I am having a rough time trying to figure out. It sounds like a loud vacuum leak, just coming from inside the intake manifold. If I put my ear right ontop of the manifold it sounds like it's coming from inside, almost like it's cracked and sucking in air, or leaking possibly the gasket is bad? I'm just not too sure what else would cause only 2 cylinders to misfire, I'm going to run compression tests tomorrow and compare 1,2 to 3,4.

mmasire88

So I just finished a compression check, and the results are as follows. Cylinder #1 165psi, cylinder #2 118psi, cylinder #3 158psi, cylinder #4 160psi. I will also add, which I completely did not think was relevant, that when I replaced the coils and plugs. Cylinder #2 the plug and coil were completely black. I thought that maybe they were stained from leaky VC gasket. I am now realizing that it may not be quite that simple. What are the chances I have a crank, on the head somewhere near cylinder 2, and it's causing blow by inside the spark plug hole? As well as low compression?

lyleswk

Cylinder #2 definitely has an issue. It could be several things: head gasket, bent valve, issue with piston ring, nick in side of cylinder, etc. I'm afraid the only way I know of to figure it out is to tear it down. Anyone else?

mmasire88

I finally figured it out, it seems that about 3/4 of the threads are stripped out. When I was redoing some compression tests. It was all over the place. One time id get 150+ another I'd get 80-90. Finally I put a dab of oil in the hole with the spark plug threaded in and on the down stroke it would suck all the oil in and vise versa on compression stroke, around the spark plug. I've did some reading on time-sert's kit and decided to give it a try seems to be a fairly easy and straight forward repair! Wish me luck! : x