P1300-Really stumped with this one!

[b7_Andy]

So as the title says I've got a P1300 code that I've spent much time trying to figure out, but have had no luck. I bought the car a little over a month ago and the engine felt great. The misfiring started very slowly about 2-3 weeks ago, I had a hard time at first even telling that it was misfiring. Now the misfires are pretty bad and it has a check engine code, but it's slowly gotten worse, didn't all happen in one day. Right away I guessed it was the ignition coil pack, or ICM, or whatever name we want to give that thing that sits in front of the intake manifold. I got a used Genuine Audi coil pack from the junkyard and swapped it, nothing changed. I tested resistance on my ICM, the junkyard ICM, and my friend's 2.8 ICM (which I know for sure is working), and they all were relatively close. Not sure if I was even testing it right, I put the positive lead on the middle of the 5 pins and tested each of the other 4 with the negative lead. Can't remember exactly what numbers I got, but they weren't far off from my friend's working ignition coil. So I figured maybe it has a bad O2 sensor. Used my multimeter to test resistance on my O2 sensors, got 2.7 Ohms for all 4 of them. I even forgot to plug one back in and drove the car afterward and nothing changed so I know the O2 sensors are good. Next the MAF... pulled it, drove it, nothing changed, so MAF is probably good. Next was pulling spark plug wires. Pulled each one, every one of them had spark and the engine ran rougher each time I pulled one. So I'm thinking everything ignition related is good. Next was fuel injectors. with the car idling I pulled the electrical connector for each injector, engine ran rough every time I pulled a connector so I'm pretty sure injectors are good.

That was pretty much all the testing I did so I'm pretty stuck. When I was driving the car every day last week and finally pulled codes, I had a P1300 and P0302. Since doing all this work I haven't seen the P0302 come back, but every time I mess with stuff and go test drive it I'm left with just the P1300. It's a weird code too because it means misfires with low fuel level. Does that mean low fuel level in the tank? Is the engine not getting enough fuel? Kind of a funky code. My fuel level sender is messed up so I can see why the car would think the fuel level is low. I'll probably solder the connection tomorrow, but don't think that will affect the misfires.

Also the misfires don't start until the car is warmed up. Once the engine's warm it starts the misfires like crazy. It idles fine, if I go full throttle it doesn't misfire that much, it's only when I'm giving the engine partial load like 25%-90% throttle. Also after I swapped coil packs and messed around with it all my readiness monitors freaked out... This is what they're showing:
This is when I thought the O2 sensors were bad, but they tested okay... Vacuum leak maybe? Yes. My vacuum reservoir was missing. It was like this when I bought the car but ran fine a month ago. I installed a new one, didn't change anything. Vacuum is still -11.8 at idle (which doesn't seem right, should be between -7 and-8? I might have a vacuum leak somewhere else). The car doesn't burn any oil at all so I don't think there's a major mechanical or internal engine problem or bad compression.

So what I think could be causing the problem:
Valve cover gaskets are leaking pretty bad, definitely some oil in the spark plug holes.
No idea on the condition of the fuel filter (car has 175,000 miles).
Possible vacuum leak somewhere but I doubt it because it would have caused the misfires when I bought the car.

I apologize for the super long post. I wanted to provide as much information as I could. I've worked on lots of Audi's over the past couple years and can usually figure this stuff out, but this one is really kicking my ass. If anyone reads this whole post and can offer any insight to a solution I would greatly appreciate! Thanks in advance for anyone that feels like tackling this one!

[Alex-A4-Avant]

Would change the fuel filter is it is a starved engine it would be pinking so if nothing changes then you know you have a good fuel filter

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[b7_Andy]

Would change the fuel filter is it is a starved engine it would be pinking so if nothing changes then you know you have a good fuel filter

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Ah I knew there was something else I wanted to check today... Forgot about the fuel filter. I pulled the pump out to solder the connection for the level sender, the wire was completely split so I got some copper wire from Autozone and I will try and reconnect it on Tuesday. I pulled the spark plugs to inspect them and they were pretty oily on the thread side (especially cylinders 1 and 4).
The spark side looked the same on all of them. They're a little old and could probably be replaced soon but no signs of a misfire on one certain cylinder. So I cleaned them up, cleaned out the spark plug holes and put them back in. I checked all my fuses, none are broken. Cleaned the MAF too while I was at it. Didn't get a chance to start the car today so will report back on Tuesday. Also my friends "working" 2.8 that I compared my coil pack to just started misfiring and won't start now... So possible ignition coil problem is up in the air still. I still think it's pretty unlikely to test 3 faulty ignition coils but I guess it's possible. At this point I'm thinking it has to be fuel filter, possibly fuel pump (I noticed that the car still has the original fuel pump and I can hear it whine when the car is running), or possibly ignition coil. I'll see when I play with the car more on Tuesday.

[Alex-A4-Avant]

Check for a hot cylinder will be browner up the white area on the spark plugs could cause detting instead

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[b7_Andy]

Check for a hot cylinder will be browner up the white area on the spark plugs could cause detting instead

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Interesting, and that would be why it doesn't start misfiring until the engine is warm right? Do you think that would be caused by bad spark plugs or fuel starvation in that cylinder?

[Alex-A4-Avant]

Possible just throughing it out there but if it's too hot on a cylinder it could be doing damage and would need to be warm to hot to do it

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[mmasire88]

I don't see it posted anywhere in your original thread, so I'm going to ask what engine is in your car? You mentioned using your friends 2.8 ICM, so I'm going to assume you have the 2.8. I ran into a similar issue last year with with A6. It out of the blue developed a misfire on a single cylinder. After a week of throwing parts at it I decided to tear the valve cover off and found a very mushy valve that I could depress with my hand. The valve spring had collapsed/broken. I was able to replace the valve spring with only removing the camshaft, it really wasn't that hard to repair at all.

Another scenario which I am dealing with as we speak in my 1.8T A4 is cracks in the cylinder head. The symptoms were noticeably worse when the car was warm, as the heat generated from the motor expand the metal and cracks. The car would just barely run when it was warm, when it was cold it ran quite a bit better. After so much diagnosing I have no choice but to finally remove the head to find multiple cracks between the valves in all but one cylinder.

Edit- I forgot to add this in here. When my 2.8 motor developed this problem (broken intake valve spring) it originated from cylinder 2. Passenger side middle cylinder, which I believe it threw p0302 misfire code. If I were you I would do a compression check on your cylinders and see if there is a noticeable difference between any of them.

[b7_Andy]

I don't see it posted anywhere in your original thread, so I'm going to ask what engine is in your car? You mentioned using your friends 2.8 ICM, so I'm going to assume you have the 2.8. I ran into a similar issue last year with with A6. It out of the blue developed a misfire on a single cylinder. After a week of throwing parts at it I decided to tear the valve cover off and found a very mushy valve that I could depress with my hand. The valve spring had collapsed/broken. I was able to replace the valve spring with only removing the camshaft, it really wasn't that hard to repair at all.

Another scenario which I am dealing with as we speak in my 1.8T A4 is cracks in the cylinder head. The symptoms were noticeably worse when the car was warm, as the heat generated from the motor expand the metal and cracks. The car would just barely run when it was warm, when it was cold it ran quite a bit better. After so much diagnosing I have no choice but to finally remove the head to find multiple cracks between the valves in all but one cylinder.

Edit- I forgot to add this in here. When my 2.8 motor developed this problem (broken intake valve spring) it originated from cylinder 2. Passenger side middle cylinder, which I believe it threw p0302 misfire code. If I were you I would do a compression check on your cylinders and see if there is a noticeable difference between any of them.

Thanks for posting up this information! And yes I can't believe with 4 long paragraphs I forgot to mention it's a 2.8 lol. I never considered any head or internal problems but I'm glad you mentioned that. It is weird how the misfires are only when it's warm. I would think if it was a fuel delivery or spark problem I would still be getting misfires since I start the car, especially fuel delivery. The valve cover gaskets are pretty shot so I should pull the valve cover off anyway and inspect. Also the car does lose coolant. The previous owner told me it leaks out the water pump and I can see it drip from the pump after I shut the car off. But I could still be losing it in other places, not sure. Definitely need to do a compression test.

[b7_Andy]

Good news! The problem is fixed, at least for the time being haha! I cleaned all the oil off the spark plugs and spark plug tubes, put them back in and that seems to have done it. I imagine that when the engine got hot, minor expansion would cause the oil to drip onto the tip of the spark plug and cause poor ignition, or something of that sort. Bottom line, oil on spark plugs-not good. Also I fixed my fuel gauge... Most people just have to solder the connection for the level sensor because it's kind of frayed, mine was completely split. So I went to autozone, randomly bought some 14 gauge copper wire, reconnected it with some solder joints and then bam, a working fuel gauge!
I'm going to change the valve cover gaskets and spark plugs to hopefully prevent this issue from happening in the future. So if you have a 2.8 and you're getting a misfire like mine and your valve covers are leaking, check your spark plugs!