# The misfires that made 3 mechanics cry



## m.caltea (Nov 24, 2019)

I own a 2008 Leon with the 1.4 TSI CAXC engine.

The misfires have started on cyl. 1 and 4 a while ago and showed no fault codes so far. 

What has been tried:

new coil pack + isolating and checking the wiring
cleaned and tested injectors (that are running fine and even after changing the position, the engine still misfires)
factory software update
new spark plugs
cleaned possible faulty sensors
compression of 10 bar on each cylinder

Does anyone have an idea on what could cause this? We are all lost.


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## Cherb32 (Jun 18, 2006)

A shot in the dark here but....how about carbon buildup on the valves? 

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## m.caltea (Nov 24, 2019)

Cherb32 said:


> A shot in the dark here but....how about carbon buildup on the valves?
> 
> Sent from my SM-N950U using Tapatalk
> [/QUOTE





Cherb32 said:


> A shot in the dark here but....how about carbon buildup on the valves?
> 
> Sent from my SM-N950U using Tapatalk


The valves are clean-ish, and the misfires happen usually when I leave the gas pedal. When the engine is not accelerating, i get sometimes up to 20-30 quick misfires then nothing.. Also no service light or errors...


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## rockport (May 31, 2016)

My guess would also be carbon build up, especially if a manual carbon clean has never been done,maybe have a look at the PCV or Crankcase breather as well









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## m.caltea (Nov 24, 2019)

rockport said:


> My guess would also be carbon build up, especially if a manual carbon clean has never been done,maybe have a look at the PCV or Crankcase breather as well
> View attachment 165934
> 
> 
> Sent from my M2102J20SG using Tapatalk


Will do, thanks. I will keep the thread updated, as i've seen this issue being left unsolved on several threads.


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