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It is a Skoda Fabia 2006, petrol, 3cylinders 1.2L.

Main problem:

  • Rough idle.

  • Misfire at random cylindners.

  • Steam, Water and black carbon from exhaust. (I'm sure it is not normal).

  • Undrivable.

Question: what is wrong with it?

Diagnoses:

Coolant level is stable and clean.

Oil is nice and normal.

It runs very rough on idle, if I tap the accelerator few times it gets more stable but falls back into a very rough idle like a muscle car.

It also feels like going between states good and bad twice or three times per minute.

It takes time for the RPM to rise when accelerating on neutral.

If I drive it, it lacks power, and after few hickups, some cylinder will misfire and I get the anti-slide and engine light lit and lose all power until I park and reset the error codes with OBDII scanner.

The error code is Misfire at cylinder X, where X can be 1 or 2.

The exhaust dripping water and black stuff, not oily and doesn't smell. just like water and carbon.

I replaced the following parts:

  • MAP sensor

  • All spark plugs.

  • All spark plugs' coils.

  • Cleaned the electronic air intake regulator or whatever it is called.

  • Air filter, Oil, Oil filter, Fuel filter.

  • O2 sensor both pre and post catalyst.

Current readings:

  • on idle, MAP reads 50kpa

  • nothing special with feul economy, since I can't drive it anyway.

  • O2 sensors pre and post cat reads 0.7-0.8 volts constantly, not ocylating.

  • Air sucking sound when tapping the accelerator, but I believe it is from the throttle regulator, not a leak, I think any way.

  • No nocking sound unless it goes into rough idle, then it really feels like an old muscle car.

  • No smoke, just visible steam and it smells like bensine or some fuel.

History in the last 6 months:

It ran 200,000Km, then I started using it for very short commutes like max 3km during winter.

  • High CO which failed inspection, fixed with Carb liquid cleaner in the fuel tank.

  • System too lean while very bad fuel economy, replacing O2 sensor fixed it.

  • System too rich while very good fuel economy (better than specs), I left it untill it started to missfire and got us here. then I replaced all the above.

  • Head gasket? .... – Martin James May 21 '17 at 20:12
  • I doubt it, there is no loss in coolant liquid and the oil looks very good. I think those are the symptoms of a blown head gasket, do you think it could be broken with no loss/foam in coolant liquid and no change in oil color/structure? – Aus May 21 '17 at 20:16
  • no, so I have nothing further to suggest:( – Martin James May 21 '17 at 20:38
2

Solved, it was a fuel injector that sprays extra gasoline.

Cylender 1 was the almost the only one that misfires although others does every now and then.

The situation becomes worse when I add injector cleaner to the fuel.

I replaced the injector and everything back to normal.

However, I noticed the oil level increased (before I figure out the injector) and became very thin, I think it was mixed with fuel that leaked from the injector.

I replaced the oil and all seems good for now.

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