2013 Audi Allroad B8 - intermittent hard start

   #21  

4lane

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Hi,
I understand that the is a intermittent problem, engine can be hard to start, one fault code that was displayed was not for day of incident?

The above N80 valve has already been discussed.

Check Air mass meter, if this fails, this will have affect on ECMs mapping of fuel air mixture, causing lean/rich, is it visually contaminated, if so clean and test again. This can also be funtionally checked with vagcom or Oscilloscope.

Using Vagcom you can monitor the rail pressure, compare pressure against time taken from start of cranking to engine start. If pressure takes time to build, could be fuel pump issue or seeping injector(s), however if pressure gets up quite fast it is getting interesting.
Either with Vagcom or an oscilloscope connected to rail pressure sender might tell you better with respect to time for pressure build up, use caution and drain pressure from rail, test again. Measure time it takes from start of crank to pressure has built up in rail.



Remember also that this engine has a control valve on camshaft, item 13 in link

https://7zap.com/en/catalog/cars/au...6751e9d28fad/manufacturer/1/627109200::109010

for variable timing, if this control valve acts up, engine can be hard to start. Using an oscilloscope for checking timing, measuring camshaft sensor and crankshaft sensor, this can tell you wether there is a longer gap between camshaft and crankshaft. If longer when engine takes a lot of cranking, suspect VVT control issue.

Regards
Gremling
Thank you for this. I replaced the N80 and thought I might have resolved the issue but after 500miles, I just had the same issue. One thing to note, it seems to happen often when the ambient air temperature is hot. I can't recollect any times it has happened when it has not been in the hot sun, predominantly after having just driven it. That could be a coincidence but would that lend any one way over another? Planning my next course of action...
 
   #22  

4lane

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Hot outdoor temperatures definitely increases the likelihood of the issue reappearing. On one recent hot day it ran rough after starting, but then ran fine after a minute. It would always run normally until reaching a stop sign. As I rolled to a stop so the engine reached idle, the idle would drop a little, engine would studder for a few seconds, and then it would recover to normal idle. It did this repeatedly during the hot drive home. Any thoughts?
 
   #23  

DrPeter

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Hello,

Hot outdoor temperatures definitely increases the likelihood of the issue reappearing. On one recent hot day it ran rough after starting, but then ran fine after a minute. It would always run normally until reaching a stop sign. As I rolled to a stop so the engine reached idle, the idle would drop a little, engine would studder for a few seconds, and then it would recover to normal idle. It did this repeatedly during the hot drive home. Any thoughts?

When you replaced the N80-Canister Purge Valve, did you happen to add the (suggested in post #15) small filter (Part number [0 450 904 058] or commonly know as the VW312) inline 'before' the N80 valve?

It maybe possible that the N80 is getting stuck open, slightly, with tiny bits of carbon from charcoal canister (part of the Evaporative Emissions system) and allowing fuel vapors to flow into the intake system.

These types filter will stop any visible contaminate and with these filters you can "see" what is inside, confirming any suspicions that the canister has started to fail and leak it's contents.

Hope that helps,

drpeter
 
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4lane

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Hello,




When you replaced the N80-Canister Purge Valve, did you happen to add the (suggested in post #15) small filter (Part number [0 450 904 058] or commonly know as the VW312) inline 'before' the N80 valve?

It maybe possible that the N80 is getting stuck open, slightly, with tiny bits of carbon from charcoal canister (part of the Evaporative Emissions system) and allowing fuel vapors to flow into the intake system.

These types filter will stop any visible contaminate and with these filters you can "see" what is inside, confirming any suspicions that the canister has started to fail and leak it's contents.

Hope that helps,

drpeter
I did add this filter, but it's clear and I am not seeing any evidence of bits of carbon getting to the N80.
 
   #25  

DrPeter

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I did add this filter, but it's clear and I am not seeing any evidence of bits of carbon getting to the N80.
Hmmmmmmm....... Glad you put the filter in-line there, but hmmm??

How about this..

Try blocking off the N80 line so that there can be no flow from the N80 to the intake. Then drive the vehicle for a while, see if this makes a difference.
You may want to remove the N80 valve and tap it on a piece of paper to see if anything comes out?

It will be okay for a while to have this blocked, maybe open the gas cap after each road test to help vent the tank.

Let us know if that makes a difference..

drpeter
 
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4lane

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I tried blocking off that line, but I didn’t see much of a change. But again, it happens so infrequently, it’s tough to determine much from a test like that. N80 seems to be clear as well. I cleaned the MAF too. A couple days later it rough started again for the first time in 3 weeks. Sigh...
 
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