P0301 Cylinder 1 misfire

[wyovino]

 

MY2000 C2 Tiptronic Cabriolet, stock intake, around 70k miles.

 

I changed out the coolant tank about two weeks ago. During the tank install, I broke the oil filler tube.  I wrapped it tightly with Gorilla tape as a few people had mentioned  that as a temporary fix.   I've driven the car about 250 miles since then with no issues. I detect a bit of gasoline smell in the exhaust but I'm not sure if it's my imagination since I had to disconnect the fuel lines during the tank R&R and I'm a bit paranoid after I work on my car.  There are no black deposits on or near the tailpipes.  Yesterday I was driving and was very low on fuel. I noticed a slight shudder every 15 or 20 seconds while I was idling at a traffic light. I filled it up as I thought maybe that was causing the shudder.

 

When I got home, I cleaned the MAF with MAF Cleaner. I started the car briefly and it seemed fine.

 

Today I pulled the car out and it was running rough immediately . Within about a minute I got a CEL P0301 - Cylinder 1 Misfire. It didn't rain yesterday but the humidity was close to 90% 

 

I had changed out the spark plugs about 20,000 miles ago but didn't replace the coils at that time, which I assume were original.  I just ordered new plugs and coils and will install them when they arrive.

 

Would a bad MAF or leaking oil filler tube trigger a misfire on just one cylinder?

 

I was planning on delaying the oil filler tube replacement to next year when I'll have my Indy replace the 7 year old LNE IMS  and the AOS.

 

Is there anything I can check in the meantime? 

 

Edited July 5, 2018 by wyovino
More detail

[JFP in PA]

It is probably the coil on that cylinder.  I would pull the coil and look closely at it, if there are visible cracks, that is your culprit.  You can try swapping the coil to another cylinder to see if the problem follows it, but if it is cracked, it is toast.

[wyovino]

Thanks.  That's what I'm hoping the issue is.  I've ordered new plugs and coils all around as they're all probably due.

[B3-CPO]

On 7/5/2018 at 4:40 PM, wyovino said:

 

Is there anything I can check in the meantime? 

 

 

I've also read about a lot of homemade patches in order to avoid not having to replace the oil filler tube, but I'm a little reluctant to say thats good advice. Seems like a lot of the more experts say that lots of problems can come about from vacuum leaks. Is the crack right at the end of the flex section? Have you tried a simple vacuum test to see if it's sucking air?

[wyovino]

It broke at the end of the accordion section. I don't believe it has a vacuum leak because the car ran great for about 300 miles before I got the CEL. I'm inclined to think that more than one cylinder would throw a code from a leak. I'm not of the mindset to do quick fixes but I made an exception in this case because I needed to get the car on the road quickly. I've ordered new plugs and coil packs and will see if the issue goes away after I put them in.  I was going to hold out for next year when I have some engine-out work done, but I'll bite the bullet and replace the filler tube now if the new coils don't fix the problem.

 

How would I test the vacuum?

 

Do you know if the glue/solvent used in PVC plumbing would work on the filler tube? The break was clean.

Edited July 7, 2018 by wyovino

[JFP in PA]

The primary reason these tubes crack is that they become brittle from heat over time.  Trying to patch a failed unit is an exercise in futility, it is going to fail again somewhere else.  Replace it.

[wyovino]

I checked out a few YouTube videos and it looks like it's a PITA, but doable. I'll order the filler pipe and address that after the new coil packs arrive.

[wyovino]

Update:

 

I changed the plugs and coils on bank 1 (ran out of time and will do bank 2 when I get a chance)

 

The plugs and coils from bank 1 looked just about perfect. There were no cracks in the coils. Once they were cleaned with a rag they looked new.  I tested cylinder 1 coil with a VOM and it compared exactly to the new updated coil.

 

Cylinder 1 coil was slightly wet at the accordion folds, but not beneath them. I'm not sure if it was oil or coolant as it was very slight. The spark plug was dry.

I didn't see any moisture on the other three coils.

 

When I changed my coolant reservoir, I pulled coolant from the tank but didn't drain the system. There was still some coolant in the lines and it leaked out once they were disconnected.  I'm wondering if the problem was caused by coolant seeping down into the spark plug tube.  I've rerouted the coolant tank overflow hose to the outside of the heat shield.

 

In any case the car is running good and there have been no new codes, but I've only driven about 75 miles so far so I'm not ready to call it fixed just yet.

 

I put a 1 1/2 inch rubber coupler with stainless hose clamps on the oil filler tube as a temporary measure until I replace it with the new one that I have on hand.