2010 Pontiac Vibe problem

Not my own car: posting for someone else.
2010 Vibe (mostly Toyota components) was running very rough and
vibrating. "Trusted mechanic" said it's running on only two cylinders,
it's not an ignition or valve or head problem, but something -- he can't
figure out what without taking it apart, and he's never encountered this
before on a Toyota engine -- "in the bottom end."
What "in the bottom end" could cause an engine to run on only two
cylinders without creating loud noises?
Perce
Reply to
Percival P. Cassidy
Bad rings or scored cylinders would do it. So would a cracked block between cylinders. The VVT-i on them can cause strange issues if they stick.
Rough and vibrating and what else? Overheating, coolant loss, oil usage? How has it been maintained overall, regular oil changes? Any codes?
Reply to
Steve W.
Has it had a compression test? Rough running, start there - and stick a vacuum gauge on it. Start with the basics.
As an aside, if it's got the Toyota 2.4 litre engine in it, then it may have head gasket issues. Unfortunately it may not be *just* the head gasket. Those engines had incorrectly threaded head stud holes in the block. They would pull out, relieve pressure on the head gasket, end with a blown head gasket. Don't know if the issue still was around in 2010. Worth checking however.
Reply to
Xeno
Rings and cylinders I would not count as "bottom end," by which I would understand crankshaft and piston rods. It's an OHC engine, so camshaft(s) and other valve gear are not "bottom end" either.
I think it's been maintained regularly as long as this person has had it. She didn't mention any other troubles. She's already bought another car, but is trying to decide whether to accept her "trusted mechanic"'s offer to buy it from her; I don't know whether a price has been discussed. I'm trying to figure out whether the problem is something that can be fixed easily and cheaply so that she can sell it as a working car at a decent price rather than as a heap of junk.
Perce
Reply to
Percival P. Cassidy
"Trusted" does not necessarily mean expert, so why don't you get a second opinion? It could be a bad coil or huge vacuum leak. It could be anything, in spite of what he said.
Reply to
Bill Vanek
The head gaskets are the dividing line, anything below them is bottom end. Except on a cam in block engine where the cam is considered part of the top end.
Reply to
Steve W.

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