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[addy]

Sorry for the misunderstanding, I am not getting any other error codes just the missfire ones.  Both Crank and Camshaft sensors are genuine Vauxhall ones. Only ever use genuine sensors for things like these, learned that from having a old Jeep that didn't like aftermarket sensors. I will remove the fuel pump relay, as the 2.0ltr workshop manual says to do it for that engine, when doing the compression test. Is the 9psi the tolerance allowed between each cylinder?

[terry paget]

Sorry for the misunderstanding, I am not getting any other error codes just the missfire ones.  Both Crank and Camshaft sensors are genuine Vauxhall ones. Only ever use genuine sensors for things like these, learned that from having a old Jeep that didn't like aftermarket sensors. I will remove the fuel pump relay, as the 2.0ltr workshop manual says to do it for that engine, when doing the compression test. Is the 9psi the tolerance allowed between each cylinder?

I would expect 9bar, or 120psi, on a good cylinder, between 0 and 3bar on a leaky one.

Putting it in context, my 43 year old Westwood lawnmower Tecumseh engine would not start, compression was 3bar. I took the head off, gasket clearly had been blowing. I could not get a new gasket, so I simply cleaned it up and put it back on again. Compression was up to 6bar. Engine roared into life on the second pull of the string. Wonderful! Hopefully good for another 43 years.

[Nick W]

120psi is pretty low for a modern high-compression engine, although if all four are making that then there probably isn't a problem.


If we're honest, a compression test is intended to point your diagnosis in the right direction by highlighting differences rather than looking for hard numbers. A leak down test is more useful, but requires rather more kit.

[addy]

I know it is the wrong manual, but for a 2.0 DOHC it says the compression for it is 12-15bar(174-218psi) with a difference between cylinders 1bar(15psi), so will use these as a rough guide and hopefully be near them or higher.

[gstylebaby]

You have checked the plugs over and the pack......Have you or the ex owner checked or replaced the leads? Could try swapping one lead over see if missfire moves to different plug.

[addy]

Unfortunately it is a complete coil pack on a 2.2, so have to change the whole thing.

[terry paget]

Haynes states the compression ratio of the 2.0 is 10:1. As the 2.2 is a detuned version of the 2.0 9-10 bars is still my expectation. As Nick says, what we are looking for is a difference between cylinders rather than the absolute value.

 My other lawn mower, a 60 year old Stoic with a Briggs and Stratton engine, 150cc side valve single cylinder vertical crankshaft splash lubricated device, a proper engine, shows a 6bar compression, and still starts on first or second pull.

[Kevin Wood]

If the compression is low enough that 2 adjacent cylinders won't fire, then it'll be obvious from the compression readings without worrying about the odd bar here or there.