slickNSX

Thanks for the link, that seems to be the exact issue I am having, surprisingly the dealer didn't tell me any issues related to fuel pressure or pump. But looks like I need to focus on this for a bit and check out pressures and see if they are bleeding off, I have a pretty strong feeling at this point that it's not getting enough gas, on a warm/hot start and I have been pushing the gas pedal down to start the car and it fires up every time this way. Cold starts are no issue at all because the car runs rich on a cold start so it's probably getting more then enough fuel at that time.

slickNSX

taking car to the local indy shop (Eurobahn in Greensboro, NC) told them the situation warm/hot start and after reading some other posts about the 3k RPM shake as well and hoping to get to the root of the problem and an estimate for fixing it. Hasn't been a good start with this Audi. I also ran my torque app on my android phone and pulled 18.6 PSI of boost, is that normal for a stock car or could this be tuned already?

slickNSX

well it turns out Eurobahn is indicating that the low pressure fuel pump is bleeding out after the car is shut off and they think replacing the low pressure fuel pump, the FPR and fuel filter replaced will fix the warm start problem, any ideas guys? Also the car has a vibration right at about 2800-3500RPM and seems like there is a TSB for this to replace the turbo down pipes with "weighted pipes" from all the reading on this the prior TSB to reprogram the electronic engine mounts did not cure this problem. So low pressure fuel pump, FPR, fuel filter and doing the down pipes parts and labor $3k. I'm still not certain after reading all the forums and posts that this will cure the warm start-up problem.

slickNSX

BTW they had the car for like 4 days, and they noticed after the car is turned off the fuel pressure drops below 3 bar and after checking with Rosstech they came up with this as the fix, I haven't done anything yet.

MP4.2+6.0

No personal modern Audi experience with it fortunately. One comment FWIW is both Audi dealer service and a lot of owners seem to have forgotten there is still the basic fuel pump in the tank, separate from the HPFP's. Thus good to see the indy is thinking that one through too. And if that pump messes up, front HPFP pumps don't get the fuel they need. They did fail on D3's pre FSI; on that era there are two with the transfer pump function across the saddle that apparently got reduced to one with some suction pump approach.

Fuel filter is a no brainer and cheap in any case. I don't really recall if/where the check valve function effectively is to avoid the pressure bleed down. You could look at the 4.0 motor SSP and see if documented there. Way back at dawn of FI for only time I ever dealt with issue it was with the tank related pump. Again, since they diagnosed pressure bleed down, it would certainly fit with vapor lock type or basic fuel pumping symptoms like it sounds like you have.

Majority of your estimate is probably the downpipes work. The pump is probably under an access plate in trunk or back seat. You used to have to drop tank on some, but these days designs often have those access plates/covers to reach. Given HPFPs have one per side, intuitively I could believe it would be the low pressure pump in tank that would logically affect whole motor instead of be more obvious on one side.