Audi A4 S4 B6 2004 engine problem

[TheRealAgent]

Hello there,

I own an Audi A4 S4 B6 2004 automatic 6 speed with 131 HP, german version with almost 175,000 KM on it. I went to Romania with the vehicle and nothing was wrong. I filled it with Super 95 and after that I noticed that something is going wrong. I guess there was some watter in the gas or watter particles. Anyhow, my engine stopped and I needed to change the fuel pump, because it wasn't working like it should. All good, for the next 600 KM, after that I recieved a fault code:

P0171 - Powertrain
System too Lean (Bank 1)

The engine was running good, and yesterday it stopped working. I tried to get in on, and got it after that, but some wierd noises could be heard from the engine, and I recieved another fault code:

P0304 - Powertrain
Cylinder 4 Misfire Detected

Alright. It didn't started yesterday. Today, at around 9 degrees Celsius outside, I started it without no problems. To mention, yesterday we got like 20-21 degrees Celsius outside. Any ideas what that could be? What should I do with it?

[gotboost]

You should be over in the b6/b7 s4 section.

[wesavk]

Hello there,

I own an Audi A4 S4 B6 2004 automatic 6 speed with 131 HP, german version with almost 175,000 KM on it. I went to Romania with the vehicle and nothing was wrong. I filled it with Super 95 and after that I noticed that something is going wrong. I guess there was some watter in the gas or watter particles. Anyhow, my engine stopped and I needed to change the fuel pump, because it wasn't working like it should. All good, for the next 600 KM, after that I recieved a fault code:

P0171 - Powertrain
System too Lean (Bank 1)

The engine was running good, and yesterday it stopped working. I tried to get in on, and got it after that, but some wierd noises could be heard from the engine, and I recieved another fault code:

P0304 - Powertrain
Cylinder 4 Misfire Detected

Alright. It didn't started yesterday. Today, at around 9 degrees Celsius outside, I started it without no problems. To mention, yesterday we got like 20-21 degrees Celsius outside. Any ideas what that could be? What should I do with it?

Pardon my ignorance, but what S4 has only 131hp? what engine do you have? which fuel pump was replaced? its been my experience at VW that we have multiple pumps on these cars. we'd need some more information about your car before we could help you diag this.

[TheRealAgent]

That it's what it's stated on the vehicle papers. Model: A4 S4 8E B6; Engine: 2.0 (1984 cm³) gasoline; Automatic 6 speed with front wheel drive. 96 kW - 131 HP, car came out in June 2004.

The rear fuel pump from inside the trunk was replaced.

[wesavk]

That it's what it's stated on the vehicle papers. Model: A4 S4 8E B6; Engine: 2.0 (1984 cm³) gasoline; Automatic 6 speed with front wheel drive. 96 kW - 131 HP, car came out in June 2004.

The rear fuel pump from inside the trunk was replaced.

if you're getting lean codes and misfires I'd check and see if there's any hpfps near the rail. might even run some seafoam or something through as well, I can't even begin to imagine the quality of fuel in Romania...

[TheRealAgent]

if you're getting lean codes and misfires I'd check and see if there's any hpfps near the rail. might even run some seafoam or something through as well, I can't even begin to imagine the quality of fuel in Romania...

Yea, well, belive me, you don't want to imagine that. Anyhow, I guess the second fault code, the missfire one should be from the spark plug. I don't know how the cylinder itself could go broke. Or maybe?

[wesavk]

well, you need 3 things for combustion, spark, fuel, and air. the lean code signals that your bank1 (pre-cat) O2 sensor is detecting too much oxygen, and if youre getting too much air or not enough fuel it could also cause a misfire. I'd still check the plugs just cause, but yeah, you might have some twigs or something in your fuel lol

[TheRealAgent]

well, you need 3 things for combustion, spark, fuel, and air. the lean code signals that your bank1 (pre-cat) O2 sensor is detecting too much oxygen, and if youre getting too much air or not enough fuel it could also cause a misfire. I'd still check the plugs just cause, but yeah, you might have some twigs or something in your fuel lol

Alright so, cleaning up the engine and everything would help but, how affected could the engine be after this?

[wesavk]

Alright so, cleaning up the engine and everything would help but, how affected could the engine be after this?

I'm not sure, I really wouldn't be able to tell you over the internet, that would take a hands on visual inspection, I know what I'm about to tell you is blasphemous but if you're concerned with that I'd take it to a dealership or a reputable shop have them give it a once over to put your fears as ease. It could be fine, could not.

[TheRealAgent]

I see, alright. Well, the vehicle is already under review in a good service. I'll wait for them to call and tell me what they've found.

[wesavk]

yeah keep me posted, I'd like to know what they find out for you

[TheRealAgent]

Will do so. They are going to look for it tomorrow.