Head Removed-Need Diagnoses Help!

[StriktlyAudi333]

-A4 B6 1.8t AMB FWD

Thought I'd share this/answer questions/take advice-

Just had to take my head off because I'm an idiot and my car loves to hate me. I was racing a V6 challenger and am proud to say that I smoked it off the line and top speed. We were on the freeway and I got to about 140 for about a mile or so but after that little adventure, I had a crank no start till about 10 to 15 cranks and then it would catch with the pedal at WOT. Ones it was warm, it would start just fine, but if it sat for 45 minutes or more I'd have to long crank it 10-15 again. I know there are several reasons why this could be but I really don't know where to diagnose the issue, being that there are multiple things it could be.

Recently replaced:
-fuel filter
-rear coolant flange & sensor
-all PCV components
-all EVAP related components
-intake & exhaust mani gaskets

I took the head off because while trying to find the starting issue, half of two plugs dropped down to the cylinders. Engine was cold and I barely had any pressure on them when I was trying to loosen them out. However I know for a fact that wasn't my starting issue.

I also (before having to pull the head) pulled the fuel rail off with injectors still connected and slid a white piece of paper under the injector tips, and over the intake mani where they go in so if I had a leaking injector I'd be able to tell. Fuel rail always held pressure and The engine sounds flooded once I'd get it started but I would run perfect fine, 100%, after about 5-8 seconds of burning out the excess fuel.

Anybody have any ideas of what my issue could be?

Thank you in advance and here is some pictures of before and after.

Car current sits with no head:

[Seerlah]

Try replacing your crank position sensor. They make the car act before it goes out, with no dtc to lead you in that direction. It's not a smart thing to throw money at parts to try and fix stuff, but this and the coolant temp sensors are sort of exceptions. CTS can be logged to show if faulty, but the crank sensor needs an oscillater. Bosch units can be had for cheap on ebay.

[Dillon Clark]

Seerlah is absolutely right! I went down the line and replaced my coil packs, spark plugs, and fuel filter, yet still had an issue with the engine dying and 10-15 cranks before starting again. It ended up being my crankshaft position sensor. Once it got too hot, it started shorting out. It's a magnetic sensor, so that made sense. I ordered one of the better ones (though not Bosch) from ECS Tuning for $55. I could have got one on eBay for $12, but I wanted the extra heat sleeve with it. Hope this helps!

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[StriktlyAudi333]

Try replacing your crank position sensor. They make the car act before it goes out, with no dtc to lead you in that direction. It's not a smart thing to throw money at parts to try and fix stuff, but this and the coolant temp sensors are sort of exceptions. CTS can be logged to show if faulty, but the crank sensor needs an oscillater. Bosch units can be had for cheap on ebay.

Thank you guys! And I totally agree about the money thing haha but I was thinking the crank sensor as well but was unsure because I had rpms while cranking? I know on heavy equipment and diesels (I'm a mechanic for Caterpillar Equipment), they don't show rpms on crank when that sensor goes but I will replace it in the Audi because that's really the only option at the moment lol. I also have live logs of pulls through all my gears but there's nothing unusual that I see (if that's relevant or not)

[Dillon Clark]

Right on man, I wanna know how it turns out.

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[StriktlyAudi333]

Right on man, I wanna know how it turns out.

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So this is where I'm at with it at the moment. I leak tested all the valve seats and ended up having to re-lap 3 intake valves. No biggie, but I found the faintest crack in the head from an exhaust valve to an intake valve. I don't don't what to do lol. It was leaking at the intake valve but isn't now that I re-lapped it to the head. First pic is with the cam caps off and what-not, second is the valves bottoms obviously, and the third is a picture of the crack if you can see it.

PS: I do my own resurfacing and machining
Cracks hard to see

[sputtle9000]

I had this same problem with my B5 A4. It confused me for a long time because the engine would sound like it was getting no compression at all. Finally I tracked it down to the downstream o2 sensor. I was able to verify this was the problem by using a blow torch to heat it up. When I heated it, the car started no problem. I recommend you give that a try.

[StriktlyAudi333]

I had this same problem with my B5 A4. It confused me for a long time because the engine would sound like it was getting no compression at all. Finally I tracked it down to the downstream o2 sensor. I was able to verify this was the problem by using a blow torch to heat it up. When I heated it, the car started no problem. I recommend you give that a try.

Thank you I will definitely try that! I appreciate the reply. Did you have any trouble codes for an O2 sensor or no?

[King5393]

Did you figure out what the issue was?

[King5393]

Did you find out what the issue was?