So, we're moving down a bit of a long winding road now - try to keep up...
The car is a 2010 Ka 1.2 (yes, I know - it's not a Fiat, but it is).

About 2 months ago the car started developing intermittent start-up errors. On the electrical side everything was fine. I decided to order some new spark plugs, as they we're closing in on their due-date for replacement anyway. It didn't really help. About 3 weeks ago I did a compression test - cylinder 2 was very low (50psi). Hmm, head gasket then? Parts ordered.

Long story short, the car started failing badly whilst I was on a business trip 2 weeks ago. I tried to assist my SO as best as I could through the phone, but from her descriptions didn't seem too bad, despite the EML going on at random.
When I got home I carried out a leak down test, and it became obvious that piston rings had gone - and the car would only run on 3 cylinders...

Decisions was made, and that brings us to today. A "new" engine was sourced from the breakers - only done 23.000km. Good deal.
Fitted it over the last few days. Started, and was only running on 3 still - turned out to be a faulty spark plug. Replaced it with a used one, and it fired right up. Went on a test drive (15 minutes), all seemed fine and well. We took it shopping - drove 2km, and the EML started flashing. Drove home, hooked up MES, and got P0300/P0301/P0304.
I took the car to work today, it runs remarkably well, and there's no sign of misfires whatsoever. The EML will ocassionally flash for 5-10 seconds, then stop. It only happens cruising at low engine load (50mph/5. gear/2300rpm).

I replaced all the spark plugs with new ones, and did an ECU reset before driving home from work.


I tried deleting the error codes during driving, and cruised along at 50mph/3. gear/3800rpm - nothing would come up. After less than 15 seconds back in 5. gear the error codes came straight back.

As the engine is running fine, my current best guess is that the pre-cat lambda was damaged during the last week of running with the old engine (with heavy misfires and 3 cylinder driving).

All sensors, injectors, coil etc. is from the new engine. Only thing from the old engine is the manicat, crank sensor and lambdas.

Does anyone have other suggestions?

Did the replacement engine come with coil packs?

Coil pack - but yes. And it is installed.

Did the engine get a new timing belt when it was fitted?

Yes, and I used locking tools and checked timing afterwards.

Did you do a phonic wheel relearn after fitting the belt?


Random misfire warning code's when cruising (without any actual misfires) is a common indicator of this being out

No, I have only done ECU reset and relearn/reset of VVT. Will try the phonic wheel reset and report back.

Relearn of the vvt sounds like the same sort of thing perhaps it'sCalled a different name on your diagnosis system?
Basically aphonic wheel relarn is to team the ECU the differing positions of the crank and cam Signals caused by changing the belt

Nope, not the same thing

I use MES, there's both VVT reset and phonic wheel relearn adjustments available.

The VVT reset is used when changing a component in that system (so I did it, as the oil valve itself is not the same) - nor the rest of the system for that matter.

Phonic wheel relearn seems to have done the job. Did a 20km test-drive after, with no error codes to follow. If I don't update any further, all is well and good.

Thank you for your assistance!