Just changed the spark plugs in my Audi A3 2.0tfsi Quattro after having a cylinder 1 misfire. The misfire seems to have gone but not the engine is now idling high. Could this be an issue where the ECU learning new parameters with the plugs? I've put NGK plugs in, and it also feels a little down on power.

  • Which model of NGK plugs did you use?
    – tlhIngan
    Commented Nov 21, 2016 at 20:03
  • Double platinum think that's what they were called!
    – Mick
    Commented Nov 21, 2016 at 20:44
  • NGK model number?
    – tlhIngan
    Commented Nov 21, 2016 at 21:02
  • What condition were the old plugs in. What is "idling high"? Is it 50, 100, 1,000 RPMs higher that normal?
    – CharlieRB
    Commented Nov 21, 2016 at 21:11
  • One of the old plugs was brown like rust and the rpm when up to 1200 from about 750.
    – Mick
    Commented Nov 21, 2016 at 21:45

2 Answers 2


The most obvious cause of high idle is a vacuum leak.

Recheck all your hoses and connections.

  • I might of knocked the maf when taking the engine cover off! I'll check all the connections when I've finished work.
    – Mick
    Commented Nov 22, 2016 at 6:29
  • Could the coil pack be goosed? Just with it being down on power!
    – Mick
    Commented Nov 22, 2016 at 10:01

I think your question about ECU parameters is spot on. Your ECU may still think it's running with the fault. Reset the ECU by unhooking the battery for 10 minutes, then reconnect and give it a try. No harm, no foul.

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