MrE16762

Hi everyone,

I need some help figuring out what exactly is the problem on my 07' A4 Cabrio, the main issue is that it turns over but stalls about a few seconds later. Trying to start it again leads to the RPM's having difficulty climbing and the engine vibrating harshly. I manage to get it to start and hold its normal idle after pressing down on the gas to force it to start but this takes several attempts. Sometimes its fine and once it starts its good to go and won't have problems while driving, however sometimes it stalls after I put into gear, at which point I repeat the process.

Some more information is below in regards to what I've replaced and other details about it that I've noticed:
- CEL light comes on and VAG scan shows codes P310B, P0087, and P0441 Low fuel pressure regulation/Fuel pressure outside of specification and Fuel Rail/system pressure too low, and EVAP Emission contr.sys.incorrect purge flow (lower limit not reached on all 3) (all 3 being passive/sporadic.)
- I replaced the low pressure fuel pump about 3 months ago since I originally thought that was the issue, the pump turns on and runs fine. (OEM Part)
- I replaced the relays for the high pressure pump a couple weeks ago. (OEM Parts)
- (This is not confirmed just some observation) The car has no problem starting up when cold, yet has issues when starting up when it has recently been run (less than an hour) might be because the RPM's naturally run higher when its a cold start therefore the fuel has less trouble reaching the engine.
- There isn't really a rough idle aside from a very slight change in the revs which I can hear while its in neutral/park, its not consistent but I can definitely hear a slight variation.
- The car does seem eat through oil pretty quickly though I think this is just because its a B7 (They drink it like water) and its got 144,000 miles on it. I always check the dipstick to make sure it never gets close to minimum.

If anyone has experienced anything similar and has had any luck fixing it, I would love to hear the insight as Im just not comfortable driving it right now since Im scared its gonna act up lol. I already ordered a new fuel pressure sensor since its a cheap and easy fix so I'll see if that does something however Im starting to believe it might be the high pressure pump. I think it's definitely fuel related I just don't know exactly which part is failing. (Keep in mind Im 20 and have limited tools at my disposal which is why I haven't just gone ahead and just started taking things apart) Any opinions are welcomed, thank you!

Hayabusafalcon

MrE
You never noted what engine you have. This car came with several options regarding engines.
1.8T?
2.0T?
3.2L?
Diesel?

We can't help you if we don't know what we are diagnosing. haha.
Hayabusafalcon....

MrE16762

Oof my fault, I got so caught up with the rest I completely forgot to mention that.

Its a 2.0T. Thanks for letting me know lol.

mmmadog

Sometimes when Audi kick out codes for fuel it can also be a electrical issue. Fuses relays sensors. I even had to have my ECM reprogrammed because car would just die. Keep after it because it does get to be a headache.

mmmadog

Also have you done the fuel pump cam follower?

MrE16762

Hey ya’ll,

So Im actually in the middle of replacing the cam follower and fuel pump since it was the most common variable between all of the research I’ve done.

I was literally on the last screw which holds the fuel pump together when I found out its head had been stripped.

The other two I was able to get off no problem but the last one thats behind the pressure release valve is stripped.

Anyone have any suggestions as to how I can get it off? I ordered the stud conversion kit to replace the screws once theyre off but at the moment thats the last piece preventing me from finishing the job. Thanks again!

Hayabusafalcon

MrE, I like that stud kit. Go for it.

Easiest way of extracting that stripped bolt is cut a grove across the head for a flat-blade screwdriver. If you don't own a Dremel tool, now is a good excuse to get one. (They are invaluable for general use and in this case a bad bolt head.) Good luck.

BTW- that bolt should not have been that tight to begin with. What is it with us grease-monkeys we gotta crank everything down so tight? Needs to be just snug enough so it does not back out under use. No tighter! Good grief.

BTW x2 - if your rig has the dreaded banjo bolt on the small fuel line then see this link: specifically #11 and #38.
B7 A4 2.0T quattro "Help-yourself Articles" - AudiWorld Forums

Haya....

mmmadog

You can also find like a 12 square bit from HF that you can pound in there that might get it out. Sucks what Audi used for bolts on their engines. If I remember right those bolts are one time use. Meaning you need to replace them when changing your cam follower. I don't get why you cannot reuse the bolts.

80sGuy

I've had episodes with my 2.0T not starting twice in 2023. Once in Jan and the last one on Nov. This happened when the engine was slightly warm or has been parked shortly and when I return to start it, the starter would only turn and sputters like an old carburetor. The first incident got me a P0506 (Low RPM Idle) code, after that I've never seen it again. There are two sensors that would remedy this problem:

1. Crankshaft Position Sensor (CKS)
Symptoms:

• Trouble starting the engine. If the sensor is not sending the correct signals, the ECU may not know when to trigger fuel injection and ignition, leading to difficulties starting the vehicle.
• Intermittent stalling. ...
• Check Engine Light is on. ...
• Poor acceleration. ...
• Fuel efficiency concerns.

2. Camshaft Position Sensor (CPS)
Most if not all symptoms are identical to both sensors.

As such, I ended up replacing my Crankshaft Position Sensor when I did the Oil Filter Housing. This sensor is located next to the filter housing on the hottest part of the engine soaked with oil around it. After replacing it I got my MPG back and it has made a huge difference. I believe this was the culprit, if not then it should be the other sensor located further up on top. Some pic and info here.