Any Audi repair gurus here?

[fanaudical]

I have a 2001 Avant with the 2.8L (it's the wife's daily driver).

It died on her in the driveway yesterday and won't start. Attempting to restart yields an intermittent "catch" where it will fire once or twice and then die.

VCDS reveals no codes. The only condition I'm aware of where it won't start without throwing a code is a bad crank position sensor. I swapped in a known good spare - still no start.

VCDS output tests run normal; injectors fire, fuel pump runs (although I haven't checked fuel pressure).

I pulled plugs, found nothing strange, replaced with new as I was going to eventually and had the old ones out. I verified I have spark on all cylinders when cranking.

Timing belt is in place and camshafts appear in time with crank.

What am I missing?

Thanks for the help.

[Nostril Cheese]

Only thing I can think of is fuel pressure.

[fastfredracing]

Try lighting it with starting fluid, and see what happens.

[fastfredracing]

Anything broken in the intake tract. mass air flow sensor boot etc... Get fuel recently?

[Rick V]

Originally Posted by fastfredracing

Try lighting it with starting fluid, and see what happens.

Use it sparingly. Ask me how I know. Gas burners like starting fluid.

[nzporsche944s2]

Could be the Coolant Temperature Sender which controls the enrichment of the fuel mixture. When they become faulty it runs too rich to the point of cutting out or not starting. I've had two fail on me in 3 years.

My wifes current daily driver is also a 2.8Q A6.

Look at the back of the engine in the middle sort of under the "Y" suction pump and you will see the sensor tapped into the coolant pipe. Check it has the green plastic plug molding not the earlier black one. Audi redesigned them because they were a known fault and even went to the trouble of colour coding the redesigned part so you can see at a glance if it's been changed.

Pelican sells them here. Even if this isn't the immediate cause of your problems they should still be changed to the updated part as a matter of course.

Coolant Temperature Switches near the bottom of this page;

2000 Audi A6 Quattro Base Sedan - Switches, Motors, Relays, Fuses & Wiring - Page 2

[DeckMan]

You can try an output test on the fuel pump. Sounds like a crank position sensor, if you get it running, you can log the rpm's in block 002 iirc, and if when maintaining a steady rpm on the cluster the reason on vag-com jumps around, then it is a bad crank position sensor.

[fanaudical]

Hmmm....She did put fuel in it 25 miles prior. I would think that we'd have sucked in any water in that 25 miles, but maybe not. I'll check that.

Crank position sensor was my first guess because of no codes, but swapping a known good one in didn't fix it. VCDS successfully logs a steady engine speed when cranking.

Fuel pump runs and pressurizes the rail, but I haven't put a pressure gauge to it yet.

I'll check the coolant sensor.

Keep those ideas coming! Thanks for the help. Happy Thanksgiving!

[DeckMan]

Coolant temp sensor as stated above can cause issues with starting. A bad throttle body can also cause running/starting issues even if it is good, it could be mis-aligned. Block 060 and switch to basic settings allows to re-align it. But by the sound of it, you might not be getting fuel. Pull that fuel line off and see when you run the pump that your getting fuel. There might also be a pressure release valve on the fuel rail that you can check for fuel pressure.

[aj748]

Have an '01 A4 Avant 1.8T 5 peed with 138K miles. Same issue a few months ago - suddenly died on the highway, would turn over an catch for a moment but not stay running. Turned out to be the fuel pump - replaced the fuel filter at the same time and all is well. Didn't show any codes with this failure mode either.

[bell]

Aj, your 1.8t also had a high pressure fuel pump which is driven from a cam follower off the cam, if the follower has not been upgraded or inspected have it checked out, when they wear out they can destroy the cam, I have seen the debris break the chain. .... and we know what happens then lol


On the v6 of the op car. ....I don't recall if the v6 uses a hpfp, but there isa separate driver module which sits above the rear fuel pump access cover, I have seen bad fuel pumps melt this module, If its there it's under the passenger rear seat position..... it converts the voltage to a pulse width signal to drive the pump.....

May be wrong, I don't see too many v6s.... and pretty much just work on porsches lol

[fanaudical]

Checked the coolant temp sensor and intake air temp sensors this morning. VCDS reports plausible value and the resistance measurement matches ambient air temp (~5C).

Reported throttle position is way off (17%) and the ECM refuses to run throttle adaptation (probably too cold). I'm warming the car to see if that works (big heat gun). I still need to check fuel delivery.

[porsche4life]

Paging Mr Hancock!!!

[fanaudical]

Well, once I got the car warmed up I managed to get it started and up to temp. I shut it off, ran throttle adaptation, and everything runs smooth again. I'll let it cool off and see if it repeats.

[Tim Hancock]

Did someone page me?

If it is running again, "I" would not shut it off and I would drive it to a car dealer with BMW's and trade it immediately for a similar year BMW.

With that said, one of the times my POS A6 stranded my wife, it was the fuel pump.

[K9Torro]

As my wife is the proud owner of an 01 TT Quat 225 6 speed and uses it for her Dailey driver about 60 miles round trip over the past several years I can tell you one thing I have figured out and that is the Audi motto. "Truth in Engineering" , the TRUTH is they have engineered a way to get all your money. All I wanted was another GTI but no she liked the TT better, bah.

Todd

[DeckMan]

Originally Posted by fanaudical

Checked the coolant temp sensor and intake air temp sensors this morning. VCDS reports plausible value and the resistance measurement matches ambient air temp (~5C).

Reported throttle position is way off (17%) and the ECM refuses to run throttle adaptation (probably too cold). I'm warming the car to see if that works (big heat gun). I still need to check fuel delivery.

17% Yikes!! How did you make out after you got it running and ran adaption?

Originally Posted by K9Torro

As my wife is the proud owner of an 01 TT Quat 225 6 speed and uses it for her Dailey driver about 60 miles round trip over the past several years I can tell you one thing I have figured out and that is the Audi motto. "Truth in Engineering" , the TRUTH is they have engineered a way to get all your money. All I wanted was another GTI but no she liked the TT better, bah.

Todd

LOL, the TT's are so much better than the GTI's They just require a little more care and feeding. The 225's are tough engines and turbo's. Mine has 167k, on the original engine, trans ect and still puts down 300awtq.