jbuddens21

Hey guys, I'm having a problem with my 2001 A4 2.8L Quattro that I've been working on for a few weeks now and am stumped. At this point the car cranks but doesn't start. I'll explain what happened but we've tried a decent amount so here goes...

A few weeks back, my A4 had been running normal until one night I went out to start my car and right away I noticed it didn't feel like the engine was running correctly. I didn't even pull out of my driveway and moments later my check engine light started flashing to which I quickly turned the car off. I tried to turn the car on once more a few minutes later to see if it happened again and same as before, I could feel mild engine vibrations and the CEL was flashing.

I didn't try to start the car again that night but thought maybe it was because of the cold (it was about 10 degrees F that night) and tried to start the car once again the next day to which it still started and gave a flashing CEL. Upon looking in my book and online I learned that a flashing CEL means an engine misfire so I quickly turned the car off knowing the problem isn't going to just go away and waited for my mechanic friend.

2 days later he was able to help me out so he came over to see what's up. I tried to start the car once more so he could briefly hear it run but this time it wouldn't even start!

The CEL codes I was originally getting were P0304, P0305, P0306 for cylinder misfires and one other code about my o2 sensors detecting faulty readouts. I read online that many misfires happen because of a faulty ignition coil so I replaced that. Unfortunately the car still wouldn't start, even while receiving a jump to ensure it wasn't from a dead battery.

We figured maybe one of the spark plugs had gone bad from the misfire. We pulled out spark plug wire #4...covered in oil. We pulled out spark plug wire #5...covered in oil. As you can guess, spark plug wire #6 was covered in oil just as bad.
Fast forwarding, not only was this issue on the right side of the engine but it was also on the left side. We took off the valve covers on both sides and the valve cover gaskets were all crusted and in bad condition so we replaced both.

I had cleared the codes after we first replaced the ignition coil and despite replacing both valve cover gaskets, the ignition coil, and all 6 spark plugs/ wires the car still won't start and doesn't give any CEL or codes.

The car cranks and tries to turn over...we can tell blue spark is coming from the spark plugs, we confirmed fuel is coming from the fuel feed line to the fuel rail, and we can see both cams moving and the timing belt looks to be connected and moving properly when trying to start the car.

Someone told us to check the camshaft & crank position sensors so we checked the resistance on them...camshaft sensors are in spec but what I think is the same as crank sensor (Engine Speed Sensor in my Chilton's?) shows a resistance of .825 ohm when spec calls for 1 ohm. I've seen people say a slight fluctuation is OK but not sure if this is too drastic and is the problem?

Other than that we can't figure out what could be causing it not to start. We've also tried most of the hopeful tricks like disconnecting battery & ecu / leaving key on ACC 3 mins / resetting codes. Anyone mind sharing a better technical knowledge on what we should try to help figure out why it won't start? I still have no codes to go off and am just trying things randomly at this point.

Thanks in advance

4Driver4

Foot to the floor and crank until it starts. Figure and cranking it at least 30 seconds.

SilverSline

Do you have VagCom? Check the values for the coolant temp. sensor. If its bad, it certainly can cause a no start.

4Driver4

I do, but it's not my car.
Did you mean to respond to the OP?

jbuddens21

So far I've only been using an OBDII Bluetooth Module and an app called Torque on my phone to scan and run tests. Part of that app allows me to check a lot of sensors, one of which was my coolant temp. It read out at 0 degrees Celsius when it was around that same temperature outside.

At the time I thought that meant the coolant temp sensor is working correctly...is the VagCom value something other than a temperature reading?

I already ordered a VagCom cable earlier this week and it should hopefully be here soon.

jbuddens21

Thanks for your response.

I've tried flooring it for a second or two but didn't do it for too long out of fear of flooding the engine with fuel.

It should be safe to do it that long (over 30 seconds)?

4Driver4

Why would I tell you to do something that would hurt the car?

Man up. Foot to the floor, crank until it starts. Expect a rough start, one cylinder at a time.

jbuddens21

Fair enough...I'll be at the car tonight so I'll post how it goes then.

Again, I appreciate the advise!

AudiMick

This is the classic way of "unflooding" a car. When you floor the pedal on most vehicles the throttle position sensor tells the ECU and cuts off the injectors.

Once the motor catches, you may need to feather it some.

jbuddens21

Thanks again for everyone's help...I finally got a chance to try this out last night.

It didn't want to start with just holding down the gas and cranking it but then I also tried the idea of feathering it. Eventually I heard it trying to catch more and more until it finally did!

Once it started running though it sounded like there was a serious valve tap or something.

I imagine the original misfire might have caused something to bend?

The tap is certainly coming from the top driver side of the engine, somewhere realted to cylinders 4/5/6 which my codes also reported as the side with a misfire.