i have a 99 a4 and i haven't had many problems with but all the sudden i was driving home from work two days ago and the car was holding at 3k rpm's doing about 75 or so then all the sudden i would lose all power and the check engine light would come one and then i heard a click of a relay or something and then all power back and no problems couldn't figure out what it was doing, it did it about 2 times after that. So the next day i went out to my car after reading a ton of forums and started my car no problems ran like a champ idle was perfect and everything else so i started driving to work and then all the sudden the problem came back but i was at low rpms this time and the car died i tried to restart and it wouldn't so i was waiting on the side of the road for awhile and then tried it one more time it fired up no problems again, so tried to drive it home and made sure that rpm's where high enough so that when the car tried to stall it would catch. Just about 5 minutes from my house the car was holding at about 3500 rpm's and then died so i figured i shouldn't try to restart it again. So i got it towed and then today i went to go and get it off the trailer and the car started up fine so i like it warm up and then switched the ignition control module off my 99.5 a4 on to my 99 to see if that was my problem well the car wouldn't start, then tried the camshaft sensor, not that and the fuses were all good, spraying eather in the throttle body to see if we weren't getting any fuel, wouldn't start again, we didn't see any spark at all but didn't know what else to do. Then we put all the old parts back on and tried starting it up after giving up before pushing it back up on the trailer and the damn car ran fine again. So i drove it on the trailer and let it ran, shut it off 4 time and started back up the second time starting i got a check engine light then the next two startups the check engine light was off so i drove it off the trailer and drove it around for about 1/2 an hour and no problems. I just don't understand what is wrong and or what i should do next. If anyone out there could help me out that would great thank you.

 

start by getting the codes thrown before you rebuild and replace parts on the whole car.

 

? bad ignition switch?
Loose connection at the ECU?

Get a VAGcom and check to see if there are any codes.

 

When you say 'all power' do you mean the motor or the whole car?


If just the motor it maybe the fuel pump.
If whole car maybe the ECU connection.

Need more info............