2004 A6 C5 Quattro 2.7 intermittent stalling and won't start

[SLine04]

Picked this up used last week, 126K miles. Seller said it had stalled a couple of times and a tech told him it was an issue with the gas cap. Apparently, reseating the gas cap may have released some pressure and it started for them. Car ran well during a short test drive, price was right, so I bought it.

Drove it about 80 miles over the first two days and it stalled once at a stop sign. Started back up fine after about 5 minutes.

Third day, it quit when my daughter was driving it. I got to her to help after about 30 minutes and it wouldn't start. Seemed to stumble a little then nothing. Left it for about two hours, it started and I tried driving home. Made it about 5 miles and it started to stumble and hesitate at low rpms. Finally died about two blocks from home. Waited ten minutes, it started and I got it home.

No CEL. I have a Vagcom reader and found no codes when checking during the time it wasn't starting. Read that a fuel pressure issue wouldn't throw a code so was thinking along those lines.

I took off the Y-pipe and pulled the coils (4 easy ones that weren't blocked) and they were bone dry. (Slight oil leak from valve cover gaskets.) Then found passenger side breather hose from valve cover was broken inside the heat shield. The rest of spider hose looked good but I removed it today with parts coming.

My question is: Could the one broken breather hose from passenger side valve cover cause the stalling issues? Idle was slightly rough when it was running so think it would cause that, but not sure that one hose would cause it to stall at low rpm and not start. Thanks in advance for any advice!

[ShelbyM3]

My initial thought was a vacuum leak, but I don’t think it’d cause your car to stall out and not restart. Tons of C5s have PCV issues, mine was nasty recently when I replaced it. I think replacing the spider hose will help your issue, but not fix it.


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[SLine04]

Thanks for the response, pretty much what I was thinking. I've read about a couple of cases where a bad crankshaft postition sensor was causing the fuel pump to turn off, no codes, so similar to what mine's doing. I have a sensor on the way.

Think I will get spider cable repaired then run it and see if it fails. When problem happens again, I can listen for fuel pump and its relay and go from there. Didn't know to do that when it initially failed.

BEL engine btw...

[SLine04]

I thought of something else to ask. I studied up on the spider hose and took it out already with a plan to rebuild it.

I don't have a good handle on the other vacuum plumbing, valves, etc. but visually it looks OK. Is there anything aside from the spider hose that I should check while I'm in there? Many crimp-on clamps I'd like to leave alone unless I need to take them off.

[ShelbyM3]

From the sounds of it, I think you’re on the right track. Just check all the soft lines under the Y-pipe that go to the fuel pressure regulator, sensors, and hard lines as they could be brittle. Another thing “while you’re in there,” sometimes the pancake valve which connects to the Y-pipe as part of the PCV system can fail. Also, it’s not a bad idea to check your throttle body boot and see if it’s torn.


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[SLine04]

Rubber parts in there really look good. TB boot looks new, maybe was replaced when serviced at 109K.

I did notice quite a bit of oil in the accordian hose from airbox and big part of Y-pipe. Would that be caused by broken spider cable?

[ShelbyM3]

Very nice!
This could be caused by a faulty pancake valve, as mentioned earlier. However, oil in the intake and Y-pipe is not uncommon. It could be bad turbos, but is most likely your faulty PCV system. What can happen, though, is oil will pool in your intercoolers and then you’ll start having performance issues.
I’d recommend pulling an intercooler hose off and see if there’s oil pooled there. A light coating of the intake track is normal, but I’ve had a car where 250mL of oil was pooled in the intercooler lines. Both sides. If that’s the case, it’s most definitely your PCV system.


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[makwaka]

Could it a faulty coolant temp sensor? It might be sending a signal that the car is overheating. I have seen these happen 2 times

[Calif_Kid]

I'm not sure if it would help, but maybe pull the spark plugs, see what brand and model they are, and see if they look like they've been firing OK, plus if there are any carbon or oil traces on the insulators. It could be something else, but it wouldn't hurt to pull the plugs and see if anything obvious is wrong. I've had two 2001 S4's and now have a 2001 A6 with 2.7T all being manual transmissions, and had some hesitation under high boost on one of the S4's (both were stage 3), and the hesitation went away with new plugs - I like Bosch F5DPOR side fire plugs as they seem to work well, and last a long time, but are pretty expensive.

If you have time, then maybe also replace the fuel filter. When I replaced it on my 2001 A6, I followed the info at http://www.audizine.com/forum/showth...er+replacement and it went smoothly. I think that changing the fuel filter on a C5 A6 is easier than on a B5 S4, but check out the link for details.

Hopefully if it is something else, you'll get a code. - Jim

[ShelbyM3]

There’s a possibility it’s the coolant temp sensor, but I thought those threw a CEL.


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[SLine04]

Thanks for the advice above, I will definitely look at plugs. Just watched a video about coolant sensor too, once I get spider hose done I will do temperature checks with Vagcom. May go ahead and order a sensor ahead of time.

[Calif_Kid]

One other thing - if you're trying to start it and it is cranking but not starting, then take a look and see if rpms are showing on the tach. I've read that the CPS (crank position sensor) can cause starting problems, so it is good to see if rpms are showing on the tach. I'm not sure if VCDS would pick up a fault for a bad CPS though. - Jim

[SLine04]

Thanks, I'll look for that. I pulled the spider hose already, waiting for hoses to rebuild it. Got related valves on the way too: pancake valve, green check valves, pcv, and the black 2 in 2 out.

Also have crank and coolant sensors coming just in case. Wish I knew ahead of time the simple things to check (fuel pump/relay, temp, and rpms) but spider hose had the bad line so it had to come out anyway. I'll be in good shape to narrow it down once I get spider hose together!

[SLine04]

I got the spider hose together and put it in today. Although I have crank speed and coolant temp sensors on hand, I didn't swap those because I want to see if fixing the known bad breather hose helps things first.

Today I just started it up and let it idle for while. RPMs were accurate, idle is lower now, just under 1K and smooth. Before it was at 1K and rough. (No CEL, there wasn't any before, but still a relief!) Also coolant temp reads normal. I will drive more tomorrow when the rescue vehicle (my daughter's after she finishes work) is available in case it stalls again.

I did check a spark plug on each bank and they looked great, a light gray and no oil. I have pictures of the spider hose I want to post here but I saved them to Google Drive. I used to know a way to change the file name to post on a forum but forgot. Any advice on where to easily store photos to post here?

[ShelbyM3]

That sounds like an improvement! I’ve seen people using Flickr recently. I just use my phone.


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[SLine04]

Well, was going to drive it some today after finishing spider hose and starting it yesterday. Today it started up, ran for about 20 seconds and quit. Wouldn't start again.

But I remembered advice about crank sensor and saw no rpm movement when cranking. I had the crank sensor on hand already so put it in. (A serious pain in the ass for something with one connector and one bolt!)

Started right up after that, rpm's looking good! Will do some road testing tomorrow and hope for the best...

[SLine04]

Thought I'd post a few pictures of this little adventure. Here's the break in spider hose to passenger valve cover. It was inside the heat shield so not obvious at first glance:
(Btw, thanks for the Flickr advice, got that to work after a couple of tries.)

[IMG]spiderbroken by Scott Franklin, on Flickr[/IMG]

[SLine04]

Here's the new hose I built, and what came out. Thought of just buying an aftermarket upgrade assembly but they were a little expensive and not all for BEL engine. So I just rebuilt it using most of the old fittings. Broke a connector but found a cheap VW hose for $5 that had two of the larger connectors on it, they fit perfectly. The main connection can was full of crap but I cleaned it out and it seemed strong. I used 5/8 silicone hose. I didn't replace the one short, small plastic hose with the small valve on it, it seemed strong.

Why purple? I hadn't seen any done in purple so why not! I also got some metal tie straps although the silicone hose is probably tight enough without them. Haven't quite mastered locking down the metal ones so some are a bit ugly.

[IMG]spiderhose (1) by Scott Franklin, on Flickr[/IMG]

[IMG]spiderhose by Scott Franklin, on Flickr[/IMG]

[SLine04]

I made one mistake. I precut the hose that goes to the pancake valve on the Y-pipe to the same length as the one that came out. It ended up being too short because the fatter silicone hose had to be routed differently. The others I made extra long and trimmed them after getting the main piece in place. Since I already had the main piece connected in the back of the engine I wasn't taking it out again; getting that connector off was the hardest part of this whole thing!

But I recovered in style; I replaced the elbow going to the pancake valve with hose. That had a small inline fitting on it that I took out and used as an inline splice to add a little extra to the short hose. You can see the splice in the next photo of things finished up. (The main piece is not all the way down in this photo, just took it to show the hoses better.)

[IMG]spiderhose (2) by Scott Franklin, on Flickr[/IMG]

[SLine04]

Here it is finished. I ran out of metal ties but ordered more I'll add later.

[IMG]a6engine by Scott Franklin, on Flickr[/IMG]

[IMG]a6engine1 by Scott Franklin, on Flickr[/IMG]

[SLine04]

A few more notes. The pancake valve was full of a lot of dried up oil. I cleaned it out and thought to reuse it but didn't know how to test it so I got a new one. The Audi part number on the pancake valve is the one for the whole spider hose assembly. The new one I got is the 1.8T part number but they
work the same as far as know. If that is not correct someone please let me know!

I was also going to replace the green check valves. I ordered them weeks ago but still don't have them. So I just took out the old green valves and cleaned and tested them by blowing through. I also got the black 2-in, 2-out valve that (I think) goes to transmission. But there is a long, hard plastic hose on one end that I wasn't sure I could reconnect. So I just left that valve in.

I wanted to replace the small black/gray (or white?) valve that comes off the elbow but couldn't match up anything to the part number on it. I just cleaned/tested and reused it. Anybody know a good part number for that?

[ShelbyM3]

Your pictures aren’t working
I’d love to see your purple setup, hahaha.


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[SLine04]

I copied "BBCode" from Flickr. Pictures are working for 3 other people I asked. Maybe that code has compatability issues with iPhone?

[ReggieNoble]

It's more than likely your CPS causing random stalling and no start issues. Also bad grounds on engine mount or under the coolant reservoir could cause stalling/ no start. And lastly a dying fuel pump can cause that (happened to me) but unlikely.

[SLine04]

Yes, it appears the crank position sensor was the problem. I wanted to drive it for a couple of days before claiming victory here!

Yesterday was fun with washer fluid tank, it was leaking from both pump grommets and the elbow output. Did a temp fix and ordered grommets. I wrapped the pump shafts with electrical tape to make them fit tighter in the grommets. Did the same with elbow fitting and also put a small clamp on it. Stopped leaking but not sure if it will hold when pump turns on, I'll try to aviod using washer until the grommets come.

[SLine04]

Well, after all that I go to start it today and won't start. I'm seeing again no tach movement while starter is cranking.

So, I replaced the crank sensor already. Could it be something on the receiving end of the crank speed sensor? I'll look again at the connection to the sensor but I'm sure the connector locked.

At least the washer reservior isn't leaking so there's that...

[pkt1213]

So I have no idea if this is has anything to do with it, but does your vehicle have a CPS spacer? I have never owned a 2.7 A6 but I will spin a short yarn about by B6 A4.

I has an 02 A4 3.0 6 speed. I sold it to my brother-in-law and he had some issues with it running after a while and took it to a shop. They put a new CPS and mostly no issues for a while but eventually ran like shit again. I bought it back and pulled the old sensor which had the end of it ground off by the flywheel teeth. Come to find out there is a little aluminum spacer they didn't swap to the new sensor but thankfully the old sensor was just hanging there because it is a part of the loom they didn't remove.

2003 S6, 01E swapped

Gone but not forgotten:
2002 A4 Avant 3.0, 01E
2003 allroad 2.7, 01E

[ReggieNoble]

So I have no idea if this is has anything to do with it, but does your vehicle have a CPS spacer? I have never owned a 2.7 A6 but I will spin a short yarn about by B6 A4.

I has an 02 A4 3.0 6 speed. I sold it to my brother-in-law and he had some issues with it running after a while and took it to a shop. They put a new CPS and mostly no issues for a while but eventually ran like shit again. I bought it back and pulled the old sensor which had the end of it ground off by the flywheel teeth. Come to find out there is a little aluminum spacer they didn't swap to the new sensor but thankfully the old sensor was just hanging there because it is a part of the loom they didn't remove.

2003 S6, 01E swapped

Gone but not forgotten:
2002 A4 Avant 3.0, 01E
2003 allroad 2.7, 01E

Yes there is....if it's lost just use a washer but you will have to grind it down some. Screenshot_2020-08-18-14-23-03.jpegScreenshot_2020-08-18-14-23-11.jpeg

[SLine04]

It had the spacer, I put it back on. The part number that went in is Bosch 261 210 217. The same but 218 came out, but think I put the right one in.

[ShelbyM3]

I copied "BBCode" from Flickr. Pictures are working for 3 other people I asked. Maybe that code has compatability issues with iPhone?

It was me. My work computer showed them fine.

Looks like you should be back up and “dependable” now.


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[SLine04]

Unfortunately not. The suspected bad crank sensor that came out checks to 941 ohms. The new one in the car reads 924. I'm guessing both are good.

Could there be crap in the hole for the sensor? I didn't check or clean it out before I put the new one in, it was hard to get to from under the car.

What else would prevent reading rpms?

[ReggieNoble]

I've seen the connector on the harness side get corroded enough to create high resistance. I've even seen some people cut it off and splice the wires together. So maybe check the resistance on the connector itself. Is this an tip or 6spd?

[SLine04]

Tip. 3-pin connector at firewall was clean. Ground there was good. Opened up the ECU box and it looks clean in there too.

Going to try to check wires from crank sensor firewall connector to ECU (I assume that's where they go.)

[SLine04]

I wanted to ohm out the wires from the 3-pin firewall connector to ECU. Found a wiring diagram for a 2.7 so disconnected battery and took off ECU connector. Pin numbers I found didn't match up so put it back together. Took off the boot on the back of 3-pin connector and wires looked good there. Connected back up but left that connector out loose and just tie strapped it.

It started again. I noticed tach needle doesn't move at all until engine kicks over, nothing while just starter cranking. Drove up and down local streets for about 10 minutes, stumbled hard one time but didn't completely stall and I drove it home.

Need to drive it for emissions test so I can get plates, will try that tomorrow but I know something isn't right.

[ShelbyM3]

Well shit! At least it’s starting and not totally stalling out. Now to figure out the stumble. Still no codes? When I had my torn throttle body boot I was getting a soft code and no CEL.


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[SLine04]

So during a little more testing yesterday it was not starting on the first try, but would on the second or third. It was at a half tank of gas so I drove to gas station and filled it up. Trouble starting on first try got me thinking about fuel pump relay. Same relay in my daughter's Passat so I borrowed it. Started on first try every time (so far) after that. Drove to emissions place and it passed.

Relay contacts on the one that came out look burned. I need some contact cleaner but I'll clean up the receptacle. Don't like the burned-looking relay contacts, wonder what could have caused that?

Need to drive more but feeling this is finally it!

[IMG]fuelrelay by Scott Franklin, on Flickr[/IMG]

[mc_hotmail]

I would open the gray cover and smell it. In any case, it's an inexpensive relay. You have great instinct.

[SLine04]

So it's not been stalling but is hard to start after warmed up. I replaced coolant temp sensor this morning but didn't help.

I drove about 25 miles to an appointment today and after sitting for about 20 minutes wouldn't start. Tried a few times then held the pedal to the floor and it kicked over. Ran fine 25 miles back to home.

I read if injectors are leaking pedal to floor will help to start. No gas smell or fuel around injectors, listened with screwdriver to ear and all sound the same. Wondering what else to look into. Check valve by fuel pump? Regulator? Or just change the injectors? Not very knowledgeable about fuel systems but ready to try!

[SLine04]

As much fun as the mechanical issues are had to take time for a cosmetic upgrade. (Didn't get a shot after completing the driver's side but they're done.)

[IMG]headlight by Scott Franklin, on Flickr[/IMG]

[IMG]headlights by Scott Franklin, on Flickr[/IMG]

[SLine04]

I got a fuel pressure gauge kit to find out if leaking pressure is causing the hard start problem. Not experienced with fuel systems so looking for help.

I plan to turn the key and see if it pressures up correctly. Then see if it holds over time. If leaking I was going pinch fo the feed line from the tank to determine if leak is from check valve at fuel pump. If it continues to leak pressure I will suspect injectors.

I'm not sure where to tap the gauge in the fuel system. In this photo, the fuel line in bottom front appears to have a pinch clamp on it. Can I just tap in there so I don't have to cut any hose? I would just use a small length of hose where the clamp is and use a tee fitting to attach the gauge. Appreciate any advice on this!

[IMG]fuellines by Scott Franklin, on Flickr[/IMG]