Preatorian

If you mean the boot between the spark plug and the coil ya. but also if there was an issue there I would think the problem would move to another cylinder when I moved the coils around. Bought replacement wires today and spliced those in for the plug to the coil. unfortunately no change. Unplugged the MAF to see if that would change anything and it ran a little rougher for a second then really back to the crappy running its doing now. I did torque the exhaust manifold bolts when I put it on prior to putting the engine back in the car and I don't hear any exhaust leaks. where is the F hose? I did replace the plastic hoses when I rebuilt the engine cause they were all cracked. also replaced all the woven vacuum hoses and clamps. wish my paranoia there would pay off!

Anyone have any thoughts about getting another ECU to try? Think I'm just wasting my money? Could the fuel pressure regulator cause this issue since its right over the number 6 cylinder that's causing me all this grief?

Texas Twin T

When was the last time you ran some fuel injector cleaner? Maybe run a can of Sea Foam in your next tank of gas.

http://www.seafoamsales.com/how-to-u...treatment.html

Preatorian

ran that in my last tank of gas before I did the complete motor rebuild. Plus I also had moved the injectors around recently after having this problem to eliminate the injectors as a possibility. Still no thoughts from anyone about possible ECU causing my issue?

s4master1

Slow down here and walk away from the car and analize the situation.
is mostly #6 misfiring, if one cylinder has large number of misfires it will cause other cylinders to misfire also, so let's just worry on #6 for now.
what is directly connected or closer to #6? brake booster vacuum hose.
is a 3 way hose, connects to the intake manifold, intake boot between the MAF and throttle body and to the brake booster pipe.
is not to hard for somebody to connected the wrong way, it has a check valve in it and when connected backwards it will create misfires in #6.
try disconnecting it from the intake and plug the intake hole to see if any change in misfires.
also even if not connected wrong the check valve can fail causing the same effect.

Preatorian

Advice well received. There's been many a time with this where I've had to just call it a night and look at it later for my sanity. Learned a lot through the process though. I've narrowed it down to the only plausible cause left. I did not consider the vacuum check valve and will take a look at that tonight. Talked to an Audi mechanic last night and his synopsis is a sticky valve which would be why its sometimes sporadic. Plus when the heads were off the machine shop only did vacuum tests and did not disassemble the vavles. So I'm going to run some cleaner in the oil this weekend and see if it helps. If not the engine will be coming back out to have a valve job done.

Preatorian

ok so a little update. Tonight I went to Autozone and bought a quart of Castrol ATF. I read a bunch of posts on the web about freeing sticky valves with ATF so I figure its worth a try. Put in the quart of ATF, started and car and just let it idle. took about 10 min to get up to operating temperature. I was advised to only run it for 10 minutes but that was just the amount of time to get warm and the misfires continued so I let it run. at about minute 12 got a couple of glimpses of a motor without misfires. continued to run. at about 16 minutes all of a sudden my misfires started slowing down. at about 20 minutes they were almost completely gone. finally stopped the car at 24 minutes after a good two minutes of running and not posting misfires or codes. So as of right now things are looking promising. going to let it sit over night and then run for another 15 minutes or so and pray this continues to improve. so far so good. too bad I already ordered the head kit this morning. guess I have my contingency plan ready.

Preatorian

Update - ATF only slightly masked the issue because of its friction modifiers. Pulled the motor out again took the heads to another machine shop and had them completely disassemble and check. Problem has been found. The issue is one bent valve over the number 6 cylinder and worn out guides all the way around both heads. My 2 and 3 cylinders were slightly more worn that the others which was why they were intermitent. Unfortunately its not cheap to rebuild both heads so it set me back a pretty penny, but atleast I now have the piece of mind knowing my motor is 100% now with everything I've done. Wish I could say the same for the transmission. So note to all if you take the time to pull the heads to have them checked do your valve seals and have them actually check the vavles. it's worth the extra money. could have saved myself a lot of time.

Preatorian

Also of note. The valve was bent just enough so that it still closed completely albeit slower than the rest but enough to have compression tests still show proper compression. Once the engine was actually started and running at a higher RPM the issue is magnified. When the machine shop checked vacuum on the heads it passed just fine because the valve was able to close. So I unwitingly assumed all was well with the valves. Wrong

evilEE

WOW! The tiniest things with this damn awsome machine! Glad to hear you found it!