Engine cutting out intermittently

[ramack]

This is about my daughter's 2007 A3 automatic trans. It started yesterday as she was driving from Denver to WY on I-25 at highway speeds(75 MPH). It has continued today as well when I took it out a couple times in town and on the interstate. The affect is worse in the city than on the highway. At highway speeds, it's slows as an under powered 4cyl would react when the A/C compressor engages. At random while moving the engine seems to stall, but not completely shut off. There is no loss of brakes, power steering or electronics, just a complete loss of power as the car begins to slow down. There isn't any odd sounds or noise. It will cut out while accelerating or while at a constant speed.

The yellow MIL in the tach face is on. But I think that turned on after she filled up with fuel before her trip. I think that's because she filled the tank too full. One thing I noticed when she arrived home from WY this afternoon is the smell of gasoline as we stood near the right rear of the car.



I haven't been able see what codes are being thrown by the OBD yet. Any ideas what the intermittent loss of power would be caused by?

Thanks,
Rich

[Silicon Voodoo]

Did you check if the gasoline cap is perfectly screwed closed? I doubt it would cause bubbles in the injection though since with a full tank there is plenty of liquid before slurping air. Also is she sure she didn't put some diesel in there or something (or particularly bad quality RON gas that causes knocking -> limp mode) ?
But the MIL is a bad sign for sure, and I'd do a wild guess that it's unrelated to the tank filling. Could be clogs of carbon that are falling of the valves, could be a vaccum leak because some hose is too old and porous. You can buy an OBD2 blutooth plug for 30$ and read it with a smartphone app.

[ramack]

Thanks for responding SV.

Did you check if the gasoline cap is perfectly screwed closed? I doubt it would cause bubbles in the injection though since with a full tank there is plenty of liquid before slurping air. Also is she sure she didn't put some diesel in there or something (or particularly bad quality RON gas that causes knocking -> limp mode) ?

Yes, I had her check the gas cap when she was on the road in WY and first called about the issue. She took it off and closed it. Not being there, I'm assuming it was done correctly. BUT...when she first bought the A3, she did have something similar with the gas cap and the MIL coming on. After Googling, most hits were about the MIL coming on were related to the gas cap not being on tight enough. Once I showed her how to R&R the cap, it rarely happened again. When she arrived home, I checked the gas cap and re-seated it, seemed fine. But the raw fuel smell from the right rear quarter panel has me wondering about a fuel leak (liquid or vapor). I didn't see anything visibly or on the driveway.

But the MIL is a bad sign for sure, and I'd do a wild guess that it's unrelated to the tank filling. Could be clogs of carbon that are falling of the valves, could be a vaccum leak because some hose is too old and porous. You can buy an OBD2 blutooth plug for 30$ and read it with a smartphone app.

She found the OBD scanner that I had put in her car, so I have that now. This morning I drove the A3 to my work, no problems with stalling. I wanted to drive it cold and then when warm to see if there was some temperature correlation. The MIL is still on, but the car drove perfectly. No stalling at all, no indication of hesitation. On a temperature note, it was hot(95-100F) in Colorado and Wyoming the past couple of days, but the temperature gauge has been mid-range, so the engine temp is good. It's going to be hot again today and I'll take the long way home via interstate to see if it acts up again. Now that I have the OBD scanner I'll check the codes when I get home.

I love driving this car! It's her first car and she was able to pick it up in a sweet deal.
Rich

[ramack]

I drove home today on the interstate trying to get the engine hot to try to reproduce the problem. It drove normal, no issues, no stalling. The MIL is still displayed. When I got home I hooked up the OBD2 scanner and noted three engine codes: 11255, 00135 and 00017. The first two are fuel pressure, the last is a cam [out of] position code.

I haven't checked yet, but I'm guessing the fuel pressure drop is related to a possible dirty fuel filter. I'm not sure about the cam sensor one, that sounds a bit more complicated. I'll be making a trip to the parts store to pick up brake light bulbs (another error thrown) and the fuel filter. I was able to clear the codes after noting the numbers and the MIL has stayed off. Hopefully I'm making progress...

[Silicon Voodoo]

I can't find anything about 11255, but 00135 seems to be O2 heater circuit. Not severe though the engine will run with no feedback from rich/lean sensor, so will build-up carbon faster.
Now 00017 is more concerning. (low numbers tend to relate to very fundamental engine mechanics).
https://www.autoblog.com/2016/03/28/...mshaft-positi/
quote

The engine may idle normally, but have a reduction in power.
The engine may run erratically or run rough on acceleration.

If this eventually requires to change the cam phaser or do an intervention in the timing chain/belt, that will cost ridiculous amounts of money.
I just had mine quoted for that + carbon cleanup at the dealership, and it was close to ~ $10k.
Audis are fun to drive for sure, it's why I can't get myself to sell mine. But they're no fun to fix.

Do the simple stuff, change the fuel filter, the O2 sensor, change the oil (it could be an oil sludge issue). And cleanup the fuel hatch area before the spilled gasoline eats through the clearcoat. Check your insurance for road service and prays it doesn't die on you in a risky stretch of tunnel or bridge. It's what I do.

[ramack]

Yesterday after I arrived home, she took the A3 out for an errand and the MIL came on at start-up. I drove it to work again this morning, before driving I checked and cleared the one code, 00017: A camshaft position (or out of position).

I have a shopping list of stuff to pick up from the parts store this afternoon, hopefully, that will take care of the fuel pressure related codes, 11255( low fuel pressure regulation) & 00135(fuel rail/system pressure too low). Those descriptions are off the OBD2 scanner.

I haven't check for causes yet for the camshaft error. Hopefully that's just a timing issue and nothing mechanical/electrical.

[Silicon Voodoo]

Well timing is very mechanical. What engine does she have? If it's the 2 liters EA113, it's a belt on the left and a chain on the right, I don't think one link can jump, but if that's what happened there is nothing more mechanical, no? If it's the sensor that has an issue, it could be due to age degradation or rust in the induction circuit. But honestly most likely shouldn't it be the phaser? Maybe get the OBD2 app, and try to check the angles of advance/retardation of the intake cam. I'm not sure of the normal values range, but if it's stuck at 45 degrees, it's broken. No loud knock noise at cold startup?

[ramack]

We went on vacation to Houston/Galveston the first week of Aug. The weekend before I changed out spark plugs, motor oil/filter, air filter and fuel filter. While changing out the plugs, 3&4 were oily(externally) so I also replaced the valve cover gasket and PCV valve. When I finished I cleared the engine codes and so far there hasn't been a re-occurrence of the MIL. I'm hoping the low fuel pressure was from a dirty fuel filter. I looked for dates on the canister, but couldn't see any, so I don't know how old it is. Most of the fuel line connectors had the release clips broken, but I was able to R & R the filter. I had read on some thread that dirty motor oil can throw the timing code. No, no loud noises at start up. Performance wise, what was really noticeable was the intermittent complete loss of power, but would the engine would stay running.

The service I need to do is the auto-trans fluid. Looks like it's called a DSG service?

[Silicon Voodoo]

Yes. DSG = direct shift gearbox. Because it's a dual clutch transmission and they wanted a brand of their own to avoid to call it DCT like everybody else.
Anyway, it sucks a lot of ATF fluid, like 5 or 7 liters, which is very expensive. But it's better to do it to avoid little metal flakes in the ATF, because they can cause shorts in the sensitive solenoids control boards.

"low fuel pressure" > this can come from a broken cam follower tappet. Since you are capable to change a valve cover gasket, this will be an easy one for you. Order the best quality part you can, no chinese crap. It costs a good 70$ at least, go to 100$ if you must. (it's an empty cylindric cover that rubs on the camshaft and protects the pressure arm of the high pressure fuel pump). Those tend to wear off and cause all sort of catastrophic issues. You can put a triple square on a spanner to open the banjo bolt under the pump easily and steady.

About the holes in the performance, did they feel like fuel bubbles (random length, short periods), or like electronically controlled with hysteresis timeouts? If it's the latter, it's probably a lump mode. Could be caused by anti knock measures, or misfire detection. idk