outlaw24

Okay. I have a 2003 A4 that has a issue when has been perplexing for me. The car takes a while of cranking to get it started. The happens only when it is cold or has been sitting overnight. Once started, the car runs fine. I have already changed the Crank Position Sensor and have verified that it is working with my VAG-COM. Codes coming back on VAG-COM show the following...

17978 - Engine Start Blocked by Immobilizer
P1570 - 008 - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 008 - - Intermittent
16688 - Cylinder 4
P0304 - 008 - Misfire Detected - Intermittent

The problem with the codes is that they only appear after a day of driving.

I have switched out the coil on Cylinder 4 and get the same code. I thought i had the hard start issue resolved but it seems to be Intermittent, which point me to an electrical issue. I have switched out the fuel filter but am beginning to wonder if a bad fuel pump could cause this. I can hear the fuel pump working....but it is louder when it is cold. Any help is appreciated. Wondering if anybody else has had this type of issue and what it was?

x19

> I can hear the fuel pump working....but it is louder when it is cold. Any >help is appreciated. Wondering if anybody else has had this type of issue and >what it was?

I think it's time to check the fuel pressure on cold morning, Good luck. x19

outlaw24

I checked the fuel pressure this morning with a gauge and the fuel pressure was between 50 and 60 psi. I put the gauge on before I attempted to start on this 23 degree morning. Yesterday we changed the Crank Position Sensor out again with a known working sensor. The car did not take as long to start today but still did not start right up. When I got to work I scanned for codes again and received the same codes as before. I never thought about the fuel pressure and that was definitely a good tip....wish it was that. Now I am thinking that maybe it is the fuel injectors on #2 and #4. I am thinking that i will be switching out the coils on #2 and #4 with known working coils just to eliminate those from the equation. I will likely just switch out the entire fuel rail assembly to make it easier.

outlaw24

Changed out the entire fuel rail assy yesterday (rail and injectors). Was hoping for a change this morning in startup behavior. No dice. Going to check timing marks today and see if the timing is off a bit. I figure that maybe the Impausible signal P0321 fault is an issue related with timing. I check ross-tech.net and they say "When an engine will not start due to mechanical (spark/fuel/compression/timing) related issues it is not uncommon to set a false G28 fault codes due to extended cranking with a no-start condition"

Prospeeder

Alot of vacuum plumbing is fed right off the end of the intake manifold, which if there is a vacuum leak would result in cylinder 4 being substantially leaned out (misfire). And the total mixture being somewhat leaned out and would make a hard start.