Misfire and start stop problems

[Radagast]

I’m hoping someone here has had a similar issue or can shed some light on the issues I have. I have a 2013 A3 1.4 tfsi sport with 44k on it. For the last few years it’s had a problem with the stop start. It works fine sometimes then it’ll stall, and if that happens the the car will run rough, until I turn it off and on which in the past cleared it. It’s been looked at numerous times by an Audi specialist but never got to the bottom of it. Battery changed, and they tried a speed controller (I think) replacement but no good. Wasn’t a real problem as I just turned it off, however: A new problem has developed, which may or may not be linked. It’s ‘soft misfiring’ all the time, only very slightly but fells slightly rough at idle. Twice it has got worse and the engine management light has flashed. Off and on resets but still slightly rough. Taken it in and misfires show up but can’t find the problem. Plugs changed, ignition coils are fine  and an air intake performed. Also filled it up with v power… still misfiring. Any ideas?

[cliffcoggin]

Those symptoms all suggest a defective battery. Was the replacement battery new or secondhand?

[Radagast]

It was a brand new s/s battery

[cliffcoggin]

Fair enough. I can't suggest another specific fault that would link all those symptoms.

[Radagast]

Now I think about it, the s/s problem went away for a day or two after I got the new battery, might be worth getting it tested? Alternator maybe not doing it’s job?

[Magnet]

Hello Neil,

Always worth checking the alternator output. Eliminate possibilities before moving on. 
Kind regards,

Gareth. 

[Radagast]

Thank you. I’ll charge the battery tomorrow and see if that solves it, if not I can eliminate that and back to square one. The garage suspect that there maybe an internal engine or valve seating problem, but to diagnose that they have to remove the cylinder head… any idea of what that’s likely to cost?,

[Stevey Y]

45 minutes ago, Radagast said:

Thank you. I’ll charge the battery tomorrow and see if that solves it, if not I can eliminate that and back to square one. The garage suspect that there maybe an internal engine or valve seating problem, but to diagnose that they have to remove the cylinder head… any idea of what that’s likely to cost?,

Hi before getting the cylinder head removed I would get it diagnosed by a specialist so that they can read the live data on the engine and see if that throws up any electrical faults whilst running.

Steve.

[cliffcoggin]

3 hours ago, Radagast said:

Now I think about it, the s/s problem went away for a day or two after I got the new battery, might be worth getting it tested? Alternator maybe not doing it’s job?

Definitely worth getting battery and charging system tested before doing anything else.

Equally definite is that you should not be getting the head taken off. If that is all you garage can suggest, go to a better garage.

[Radagast]

Battery was 12.4v when I tested it about 30 mins after driving it. I’ll leave it on overnight. 

Garage is a non franchise Audi specialist and I have faith in them. 

[Magnet]

Thanks Neil, but testing the battery ‘at rest’ with a simple multi meter is virtually meaningless. You will need to get it tested using specialised equipment. Halfords etc. should be able to do this, but I have known batteries to even pass this test, but not being capable of satisfying all parameters monitored by the battery condition monitor - if fitted. 
Kind regards,

Gareth. 

[Radagast]

Thanks Gareth. Leaving it on charge overnight and then seeing if the problem is still present tomorrow is a viable idea though?

[Magnet]

You can try Neil , but not really an acid indicator of the battery’s efficiency Neil. 
Kind regards,

Gareth. 

[Radagast]

Thank you

 

[cliffcoggin]

1 hour ago, Radagast said:

Battery was 12.4v when I tested it about 30 mins after driving it. I’ll leave it on overnight. 

Garage is a non franchise Audi specialist and I have faith in them. 

A simple voltage reading will not tell you if the battery is fully functional. It needs to be tested on a high discharge test rig.

[Radagast]

Clifford, I’m in Kent too. Do you use a non franchised Audi mechanic? Can you recommend one please 

[cliffcoggin]

58 minutes ago, Radagast said:

Clifford, I’m in Kent too. Do you use a non franchised Audi mechanic? Can you recommend one please 

Yes indeed.

https://msautoservices.com/

is the place I took my A3 to. The owner, Michael Summers, is the person who alerted me to the problems a substandard battery can cause for the ECM and other delicate electronics, while allowing electro-mechanical equipment such as the starter and the wipers to function normally. In my particular case I would sporadically lose air conditioning and cruise control, and the engine would go into limp mode. A new battery fixed the problem.