Re: Is this my big end bearings gone and has anyone ever changed them?
Doing the big end bearings is possible in the vehicle, however if the crankshaft has sustained damage and needs a regrind, you will need to remove the engine.
To check the big ends, you need to remove the exhaust, and sump, (and dont forget the oil!!) also a couple of other pesky bolts
Then once the sump is off remove the big end caps, DONT MIX THEM UP!! and check the bearings. (if there is any scoring or damage i am afraid its a engine out job and a regrind.
To be honest dan we change and recon approx 20-30 engines a month and its very very rare a bottom end can be rescued in a car. (even timing belt failures take the mains out)
However the symptoms dont sound to me like a big end failure. I would eliminate the following first
1) remove the plugs, check they are intact - could indicate a dropped valve if they are damaged
2) run a compression test, look for differences between the cylinders this could indicate again the above, or even ring failure
3) check the obvious, headgasket failure - mayo, back pressure etc coil pack failure, get the car read with alfa diag, and check for smoke
before taking the engine to bits, try running the car, unplugging injectors one at a time, (this reduces load in the cylinder as the compressed mixture is not been ignited) and see if the pitch changes.
If i was to guess i would say a dropped valve, its very common, we get at least 5 a month. sadly it usually means a total rebuild.
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Hope that helps.