AudiHip

Don't know about newer S*, but problem on older Audis:
Check failing Ignition Switch often caused by too many keys - works cold, poor or no start after even short drive;
Same for 'cold start' injector sys. leaking inc. Faulty Emission control system.
Check for Carbon buildup inside intake sys. that Audi is 'ignoring'!

phydor

Hi there guys, i really have a problem with an Audi S7 4.0 TFSI.What could case sluggish engine running and stopping with no errors whatsoever?If it s cold, it runs for 2 minutes and afterwards starts to stutter and eventually stops.In order to run again i must press the acceleration pedal along with brake pedal and it stops again after starting.If i continue to accelerate it, it has serious backfiring.I left the car at two Audi dealers, what they managed to do was just to destroy my turbos.So I bought new turbos and after 100 kms the car started backfiring again and trashed these turbos also.I took the car back from the Audi dealership and changed the ECU.Still same behaviour, i got just misfiring on cylinder1.I changed all of you could think of, HP pumps,spark plugs,ignition coils, etc.I can make a small movie and upload it here if it can help.

slickNSX

wow sorry to hear, how many miles are on the car and what year is it? Also when you start cold does it run smooth until the backfires start? I've noticed my car runs on cold idle for about a minute then the idle goes down to normal RPM range, this sounds like a bad idle air control motor so far but that would've been an easy catch for the dealership, as far as turbos burning up that quickly can't really help you there, that sounds very odd and expensive.

MP4.2+6.0

Low tech: bad brake light switch as one long shot? Brake switch causes throttle to cut back.

From D3 (4.2 V8): Maybe the engine crankshaft position sensor? Crank sensor is essentially ground zero for all motor controls, telling ECU where the motor position is that everything else relies on. Known D3 failure point, and also known that is may not show any codes--sometimes does, sometimes doesn't. Also acts erratically on D3 often--not just an outright failure.

phydor

I think that was the first thing I changed.In the past it used to work for 2 hours then started to rattle.When it starts to do that, i get backfiring when accelerating because if i don't , the engine stops.I left the car at audi dealership, they replaced the turbos and they broke in 100 km during test period. (the new ones).They told me to buy new turbos or eventually a new engine.That's what the Audi dealership said.So I got the car back and I'm trying to figure it out but I'm running out of ideas honestly.Could a bad wiring cause this? I ve seen that the wiring for the right hand of the engine has some parts with melt protection.I have ODIS and I can do whatever tests I want.I m gonna try to block the engine in 4 or 8 cylinder mode, maybe I'll get some results.It's been a year since it's not running and it drives me crazy.

phydor

Hi there guys, the car's problem is ****in bizarre.So, by checking all possible causes, my brother unfilled the oil cap and BAM!, car idling again!We had some fun with covering the hole for a few times.Actually the vacuum created there was so great when I was accelerating that my brother barely could lift his palm from the oil cap.We stopped the car and when we started it again, it continued to idle flawlessly even if we put back the oil cap.We are indeed baffled because since then the car runs as it should and I couldn t reproduce the issue that the car had for over a year.I leave the videos to see for yourselves.Anybody, any idea? I m guessing some kind of throttle body glitch,I don't know.It has to do it again to investigate further.
So,with oil cap off : After 10 minutes with oil cap on, running smoothly :

Q Banks

where is the high pressure fuel pumps located? As I’m aware that the Audi has a "in tank" fuel pump (and because there is 2 tanks there is two needed)

but it where is the HPFP’s located? Thanks

Scott DeMarco

https://static.nhtsa.gov/odi/tsbs/20...55649-9999.pdf

AUDI TSB # 01 19 00 2046724/7

which superseeds the technical bulletin theyve know about this problem for a while! Technical Service Bulletin Group 01 number 18-73. It looks like Audi has know about this since 2017

Jari Kuusisto

My Audi A8 2015 4.0 TFSI had an engine failure at 29.500 kms. Microfilter was blocked and prevented oil supply to turbos. Engine has now been rebuilt but a couple of ECS failure codes persist.
- Engine revs limited to 4000 rpm. Typically this happens soon after engine has been started. Often when car is turning sharply. The failure light sometimes goes off once you drive a bit longer.
- In the occasion rpm limit goes away, the engine start stop system shows failure code
- the third problem is related to misfiring
I suspect that these codes come from variable valve system solenoids, or sensors. The failure code indicates that the variable valve system reacts too slowly.
I understand that this is rather a typical prblem for Audi A8 with 4.0 TFSI engine. I have installed ABT tuning box to my car.
Any ideas and help would be greatly appreciated. I have already spent a lot on having the engine rebuilt.

Luis Trevino

After reading so many post about the issues. I had the dealership in my area take a look at issue. Car was flat with the dealer for two days. The fancy tablet apparently didn’t find any faults in the system. I asked if the tech took the oil cap off and smelled for gas in the crank. (No reply to that question). After having a conversation with my trusted Audi garage that has been taking car of my past few out of warranty Audi toys the past 10+ years. I requested that both upper high pressure fuel pumps be replaced. So far no issues for report after two weeks. Cost $1,800 at the dealership. Fuel pumps each were around $550.