Random Misfires

[jdmnomore]

Hate to start one of these threads but my situation seems to be a bit different than what ive found by searching...

Yesterday im heading home on about a 2 mile trip. Halfway there outve nowhere the car starts vibrating under load pretty bad and i get the ol flashing engine light. No loud noises or anything prompting this change in behavior it just happened. I limp home the remaining mile or so and my buddy comes by with his scanner (not VAG). The car is throwing random misfires in if i recall cylinders 1,3,5,7 or something. Shut the car off now its 1,4,8 etc.. basically random. At idle the car sounds like a cammed LS car i smell fuel and it wants to shut off but wont. My serp belt is fine, no fluids under the car and coil packs were replaced under the recall. Spark plugs have been on for about 25k however from what ive read im on the fence as to whether they may be the culprit.

Any suggestions people as to what is going on before I send this thing to the stealership?

[Joey]

Sounds like the car might be struggling for fuel? Maybe the pump is dying on you?

[jdmnomore]

Joey that sounds spot on. The pump has been extra loud as of late. Also I had a couple cold start issues where the car would start and idle rough like it wanted to die and then recover, like when the fuel pump is dying. So this would cause these types of misfires + fuel smell + vibration when accelerating?

To add some details I was able to cycle the car about 3 times it appears to build pressure which is why I didnt think fuel pump. The main question I have is what would cause to misfire in different banks randomly.

[Joey]

Joey that sounds spot on. The pump has been extra loud as of late. Also I had a couple cold start issues where the car would start and idle rough like it wanted to die and then recover, like when the fuel pump is dying. So this would cause these types of misfires + fuel smell + vibration when accelerating?

Well, lets look at it like this. If the car was getting no fuel it would not start or run, period. With a little bit of fuel you can still run the car, but you are not injecting a sufficient amount into the combustion chamber to ignite and run properly. This would surely cause the misfires that you are experiencing. The vibration you are feeling is the misfiring and stumbling of the motor trying to do its job without the proper amount of fuel.

The fact that you smell fuel only enforces the assumption that it is fuel related. It could be a couple of things. Either you have a bad leak (you would be able to see it somewhere), the fuel lines are clogged, or your fuel pump is on its way out. I am thinking the latter with the way you have described everything.

[jdmnomore]

Joey once again I appreciate your help. Now to find a fuel pump at a decent cost.

[jdmnomore]

Joey what do you think about it possibly being the crankshaft position sensor?

[Joey]

Joey what do you think about it possibly being the crankshaft position sensor?

It is another possibility. Did you have any sensor fault codes from the VAG readout? Can you print the result?

From the symptoms you have described though I would start with the pump. I believe it is cheaper than a new camshaft sensor.

[jdmnomore]

Unfortunately all I was able to use was a generic scanner and the only codes were random misfires. Its funny you said "camshaft position sensor" also because ive seen both that and crankshaft position sensor mentioned which is confusing. Im thinking of just going ahead and ordering VAG from ross-tech or whatever and waiting til that arrives.

So all that being said, im under the hood today and I noticed something very odd and concerning. No idea if how this would contribute but check out this pic.

That residue on my coilpack wire is coming from the coolant tank directly above it. I ran my fingers below it and there is a lot of that residue on the bottom of the coolant tank itself as well as a bit of moisture. My coolant levels are a bit low also right at the min line even though I added some not to long ago. Im stumped as to what is going on there and if it could possibly have contributed to my issue.

[Vee8s4]

The coolant tank is prone to cracking and leaking. Not sure it's related to your misfire issue...but definitely something you should fix.

[jdmnomore]

Thanks for the info Vee will get that squared away. The more I read the more confused i get. Whats interesting is the car cranks and builds pressure everytime. The fuel pump is barely audible but I swear I hear it priming. These two things are causing me to lean away from the sensor or pump although ive been thinking my pump might go for quite a while. Anyhow now what im thinking is maybe the intake manifold bolts got loose somehow. Going to call a friend tommorow to see if I can use his tools.

Will keep you guys posted on this. If I cant figure it out tommorow I think the car may end up at the stealership and god help me if that happens.

[Joey]

Yeah, coolant tank cracking is common. Cheap fix. A brand new expansion tank is only like $20 bucks.

Keep us posted

[jdmnomore]

Bad news from the dealer. No compression in cylinder 1. Possibly a dropped valve but the tech says he has to dig in to the motor to know for sure. Car had no chain rattle, burned no oil and was literally babied rarely ever driven hard. I dont understand how this could have happened.

[Type_Audi]

Dude, sorry to hear that.

Lets hope it is just a dropped valve. Did it make any metal on metal type of sounds when this started? Hopefully no metal-metal contact occurred.

[Joey]

Damn man. Really sorry to hear about this. Lots of engine failures occurring lately.

[norcal]

Damn man. Really sorry to hear about this. Lots of engine failures occurring lately.

lots of people entering the 100k+ mile club

[jdmnomore]

My car actually just hit 75,000 miles not to long ago I wish it wouldve made it to 100. I appreciate it though guys just trying to wrap my mind around this thing. The car is under warranty for another month but Im skeptical that they will be proactive about taking care of this. More than likely this ends up as a complete loss unfortunately I purchased this car when I was young and dumb and now I will deal with the consequences of over extending yourself financially to afford a car. Joey I may PM you if it looks like I have to dump the car b/c I have no idea how that even works and I know youve dealt with similar scenarios.

[Joey]

My car actually just hit 75,000 miles not to long ago I wish it wouldve made it to 100. I appreciate it though guys just trying to wrap my mind around this thing. The car is under warranty for another month but Im skeptical that they will be proactive about taking care of this. More than likely this ends up as a complete loss unfortunately I purchased this car when I was young and dumb and now I will deal with the consequences of over extending yourself financially to afford a car. Joey I may PM you if it looks like I have to dump the car b/c I have no idea how that even works and I know youve dealt with similar scenarios.

Let me know man. Hopefully i can help you out. Call me if you want to talk