My Audi A4 has been having trouble starting for about 2 weeks. If it would fail to start, I would let it sit for about 30 mins, try to start again, and it would start just fine. It is cranking just fine, turns over, sounds as if nothing is wrong, it just won't start. We came to the assumption that there had to be a problem with fuel getting to the engine, so we replaced the fuel filter (it needed it anyways) and noticed the fuel pump wasn't working. So, we first checked the relay which was broken. We replaced the relay, the fuel pump is now working fine, but the car still won't start. The check engine light is on, but the only code that pulls up is a cylinder misfire, & that has been on for a while. The ignition switch was replaced a couple of months ago, we are running out of ideas on what's wrong with it. Any help would be greatly appreciated, this is my only car and I drive daily for work and school.

 

Try this before going any further. Disconnect the battery (both terminals) and touch them together. Leave them off and let it set for an hour or so. Reconnect the terminals, positive terminal first then the negative terminal. Put the key in the ignition and turn the switch on but DO NOT try to crank it just yet. Let it sit in that position about 15 seconds before starting. It may stumble on start-up at first but it should fire. This process clears the ECU of any trash data that may still be in there caused by the faulty fuel pump relay. Sounds weird but sometimes it does work.

 

I'm very skeptical of doing this, considering that unhooking the battery will result in me needing to get a throttle body adaptation done (we have unhooked the battery terminals before and it has done a lot worse than it did good), and I don't have VAG-COM to do the TBA.

 

You should not have to do a Throttle Body Adaptation once it has been adapted to the ECU. only when you actually put a different throttle body on it do you have to do a TBA. I've disconnected the battery on my D2 A8 many times without an issue. Back in July, I had to put new chain tensioners in the heads of my 4.2. The battery was disconnected for about 3 and half weeks. Like I said, the engine will stumble and possibly run rough for a few seconds when you do this. The ECU is relearning the engine in those first few seconds.