Auditoy01

Ok so I am new to this. The other week I pulled the codes on my 01 Audi A4 Quattro 1.8T it gave me P0300, P0303 ,P0304, P0038. After alot of searching we replaced the spark plugs, and found the firing order, and followed the misfire by switching coil packs then replaced the coil packs that we thought were bad. The car ran fine for a few days no problems at all. Yesterday while out driving the CEL flashed once then went off. I brought the car home hooked up the code reader and it had pulled P0300, P0301,P0302. I cleared all the codes and we took it out for a drive to see if it would happen again.....it took about 15-20 minutes before it did but once again the CEL light flashed once and then went off and the same codes pulled. When we originally followed the misfire we swapped out 4 to 2 so 2 has a brand new coil pack in it.....could it be bad straight from the store? and why is 1 now misfiring??? We do know that it needs a valve cover replaced and we have it already just not got it on. Could that be causing the misfires???? I need help PLEASE!!!

mtroxel

You might have to get more technical with this one. Bentley has some good proceedures for diagnosing a P0300, but you need a VAG-COM so you can read Measuring block 14. The ECU needs good information to fire those cylinders, and given the logical steps you've taken, your problem might be elsewhere.

The engine speed sensor comes to mind right away. Bentley tells you how to test that too.

The price of a Bentley is a lot less than a trip to the dealer.

jseklund

Yes, as stated above, the Vag-Com can be a huge help here. You can use it to clear all of the misfires, start the car and then watch each cylinder to see which is misfiring. It counts the number of times a cylinder misfires for each cylinder - so if you start them all at 0, you can narrow it down to the one or two that are misfiring the most.

Also, I've had 1 coil pack cause misfires on 3 different cylinders. It threw things off just enough that the cylinders following that coil would misfire. The vag-com was very handy with this and saved me from having to replace all three packs.

Auditoy01

Ok so we had the car out running today and the CEL light came on...no flashing this time and started throwing codes P0038, P0136, P0171. I am so confused now cause I know the first one has something to do with a o2 sensor circuit high, the second one is a o2 malfunction (which is crazy cause both o2 sensors are brand new) and the thrid is the engine is running to lean....but there are no vacuum leaks we have already smoked the lines trying to find a leak. The car ran fine up until a few weeks ago when we put a aftermarket air intake on and since then have been having so many problems....How could making one mod cause all this??? And what is a VAG COM?????

jseklund

A Vag-Com is software and a cable that allows you to use a laptop to connect to your car's computer.

http://www.ross-tech.com/

Everyone who does not own it waits forever to buy one because it SEEMS expensive. The tool will save you hundreds on its first few uses though.

The first place I would look is at the wiring to both O2 sensors. Did you pinch one, pull on one, etc? It looks like you may have a short or an open in the wiring.

Beyond visual inspection, grab your multimeter and follow these two articles:

https://www.audiworld.com/tech/eng101.shtml

https://www.audiworld.com/tech/eng62.shtml

jseklund

One other thing to try, although I doubt it's the case - if you used an oil-based air filter in your new intake, you may have gotten this oil onto the MAF...I don't think this is it though.