rogmac1175

So I have a 2004 A6 3.0 Quattro. I've had it 6 weeks. Since I got it, I have an intermittent starting issue. It always starts and runs fine, but sometimes it takes 5-6 seconds of cranking when it starts.

I have had it to the mechanic a few times. They have changed out the Temp Sensor and the Thermostat, and checked for vacuum leaks. They checked the battery which tests fine (plus, it cranks good and hard....just doesn't catch).

I have had them check the codes and I have checked them myself. Nada. No codes in the system and none pending.

Any idea folks? At some point I am afraid it's going to let me sit.


Thanks!

SloopJohnB@mac.com

Check fuel pressure before starting using mechanical fuel pressure gauge. You'll have to plumb it in and start the car and then let the car sit overnight. You might be leaking fuel from one or more injectors or the check valve in the fuel supply isn't.

rogmac1175

Would that be an intermittent problem? This only happens once a week or so.

I should mention that I am at 63,000 miles and they have also checked the Crankshaft Position Sensor and done the whole "relearn the gears" thing.

jcman

If your plugs are factory original change them, at 63k its possible they have never been done.

I have the same year and engine since 08 with 84k now and at times I've noticed the same thing not all of the time before the 55K coil pack and plug change and up to now its once in a blue moon with a 3 second crank before she fires.

The CPS has two codes one warning you and the other you already know because it ain't going to start "period" and be a flakey one when intermittent hot to cool then it signals, very cheap part for a going on 10yr old car.

rogmac1175

So jcman are you saying even without a code I should replace the CPS? If it's not real expensive I guess it may be worth a shot. I love this car otherwise so it's worth fixing for sure.

The other problem I should mention....and this may be normal....is when I turn the car off, it "winds down". Sounds like a jet engine shutting off. Kind of like a loud turbo spinning down. Fans maybe? Any ideas?

jcman

Maybe, if your engine is at operating temp and you try to restart with issues its a good start based on the age of the part.

You never answered us about the age/miles on the plugs?

If you're running the AC and you shut it down you will hear a massive fan noise for a couple of seconds, both fans are electric on a 3.0, try opening the hood and have someone shut it down and verify its the fan along with running it with out AC.

rogmac1175

Cool. So yes, it's the fans. And it doesn't happen when on "ECON" which I am assuming turns off the A/C.

As for the plugs, I just got the car and I am assuming they are original. I have 63K on the car.

Airbag

im thinking that is going to be a cam or Crank sensor. That is exactly how my Audi 90 cam sensor failed ..

intermitent no signal, and it wont start , but if it was running the sensor would die and the engine would default and not advance timing but still run.

i admit this is OBD2 with highly evolved electronics compared to that car but im thinking the principles are similar

jcman

Well kinda sorta Airbag, the 3.0 has variable intake and two step exhaust timing with many more cam related codes.