2010 a4 will not start

[robc]

First post on here, stock motor was driving today motor started to run really rough pulled over in my driveway still idling tough turned on and off a few times still running rough now will not start back up. Scanned it po300 and p0303 random misfire and cylinder 3 misfire. Replaced coil pack on #3 still will not start just cranks the EPC light did come on before the last time I shut the car off Any ideas?

[The Infiltrator]

I would post this here. Did the codes come back after you cleared them?

[van462]

A few possibilities, timing chain may have jumped a tooth or a fuel injector may have become stuck open. What type of scanner do you use?

[robc]

The codes did come back up, I am using a Mac

- - - Updated - - -

Mac tools task code scanner

[Gunnark100]

To many possibilities, not bad link for this error:

http://www.autocodes.com/p0303_audi.html

[robc]

I would think if a injector is bad the car should start but run really rough also the mileage on the car is 38,000.

[van462]

The codes did come back up, I am using a Mac

- - - Updated - - -

Mac tools task code scanner

You should be able to read sensor data with that. You could monitor fuel pressure on the high pressure side. At idle mine indicates 561 psi. If you cut off the car the fuel pressure shroud stay in the 500's if it drops off then likely a stuck injector. You usually have a strong fuel smell in the exhaust and often white smoke when cranking.
One cylinder usually won't stop a car from running unless its dropping fuel pressure so low that the other cylinders are starved. Eve then I would think a low fuel pressure light would illuminate.
If the exhaust cam has jumped a tooth on the timing chain you will not get a code other than misfire. The ECU monitors the position of the intake cam to the crank when/if it gives a timing code. The upper timing cover is fairly easy to remove. 5 bolts plus 1 or 2 screws that holds the "dipstick tube". Have the car on ramps, remove the lower shield and rotate the crank (having spark plugs removed makes this easier). Check cam sprocket to chain timing mark alignment. If the tensioner has gone bad the amount you will see the cams and chain jump around when you rotate it will be scary looking. This failure can destroy a head very quickly.

[robc]

I hope it is not the timing chain tensioner. Will it fail with only 38,000 miles. Also there was a burning smell in the car when This all happened today. And when trying to start the car by pressing the key in the motor will stay cranking after the key is released and not stop till the key is pressed again

[van462]

The early years have a tensioner design that relies on oil pressure for chain tension. After engine shutdown tension was maintained by a spring loaded racheting pawl. If the spring breaks then you lose chain tensioning during engine starts. So a low mile vehicle can be affected, one that is used on short trips even more so as it will have gone thru more start cycles.
Pressing the key initiates a stay sequence that runs without having the key pressed in. I don't know if it's time or number of revolutions based. Trying several start attempts creates a lot of starter heat. You may have smelled that, but who knows.

[robc]

Thanks I will try to check the timing marks tomorrow. Sucks it died on the side of the street Will the cam or crank sensor be a possibility?

[robc]

New update this morning took a better look the car started very hard white smoke pouring out of the tail pipe hooked the scanner up while the car was running open fuel system 1 came up and misfire #3. Pulled the plug soaked with fuel. So looks like a bad injector replace all of just the one?

[van462]

Injectors warranty was extended to 70k or 80k as well. Unsure how vehicle age works into this. Give audi a call you may get them done for free. I believe they replace all four when they do it.

I wonder if letting the car cool down allowed it to start. If an injector is stuck spraying fuel it ends up washing down the cylinder and into the oil system. It flashes off in the hot oil and the PCV system sucks this now fuel laden mixture back into the intake, the N80 vavle is also purging gas vapors from the charcoal canister as well. The resulting air mixture may have gotten too rich to burn in the other 3 cylinders.

[robc]

Thanks!! I called today my factory warranty ended on 5/25/16 smh. The lady didn't want to know anything said they will need to do their diagnostics at $135 hr. Then I asked about the oil consumption she said my car has no complaints hard to believe everyone I talk to with a 2010 a4 needs a quart of oil every 1500 miles. This will be the last Audi I will own. But I will try again with the extended warranty on the injectors

[van462]

I read on another forum the injectors went to a 10 year 120K. You may be better off talking to the dealership service department vs AOA. The service department will likely be reimbursed by AOA for their work so they may actually help you on your path. I would expect a diagnoses fee up front that may or not be reimbursed.

[robc]

Thanks will definitely call the service center again tomorrow I think I just got a girl on the phone who didn't know anything

[robc]

Update picked it up from the dealer injector replaced under warranty. Thanks for all the help

[van462]

Glad it worked out well.