[Non Corsa] Astra G Misfire

[Baronoli]

My friend has bought an Astra G. Started to misfire when starting up after a 20 minute drive from dealer to the service station. It eventually starts with a bit of revving.

Since then, it sometimes misfires every now and then. I've changed the sparkplugs for him. I noticed they were the wrong plugs, all of them sooted quite bad and all had different distances on the plugs. Next up is an oil change on the list as it hasn't been serviced in 2-3 years... Is there anything I should try next?

It's a 1.6 8V, 2002 Astra LS.

Thanks as always!

[Taurus]

With sooty plugs and misfiring once hot it's worth considering the coolant temperature sensor. They default to a cold start mix, so if the sensor is weak the mix will be rich. Depends how it misfires - a rich mix will cause idle issues and lumpy running, but it ought to run fine on full acceleration. But if it hasn't been serviced then check the state of air and fuel filters first.

[Baronoli]

Thanks again! I completely forgot about the CTS, it's the X16SZR engine, there are two types of CTS on eBay it seems. I'll send him to Vauxhall and fit it when he gets it.

On a slightly related subject, do you know the size of the drain plug socket size? It looks about 19, but I don't want to risk rounding it off. I have bad luck with oil plugs as it is.

[Baronoli]

All fixed so it would seem. The service went well, done an oil change and after 50 miles or so the oil was still black, going to change again after a while. I cleaned a few bits with some carb cleaner and it hasn't misfired since. CTS was only recently changed too, found a receipt stapled in the history.

Thanks!

[Taurus]

Sounds good. Re. the oil, I'd leave it in for say 1-2k then change it, then stick to 5k intervals. The fact that it goes black quickly says it's cleaning the engine effectively.

[Baronoli]

What kind of oil do you suggest just for a 2k change then, if it is still dirty? He went and got Castrol before. I know the Vauxhall oil is pretty good, trying to save the guy a bit of money if it's just a few short term changes though. Thanks!

[Taurus]

Basically any half decent semi-synth is good enough if you're doing some quick changes. GM oil is good, but it isn't cheap. For that kind of thing I use Drive-Tec oil from CES. Comma is good, and it isn't expensive.

[Baronoli]

I'll pass on the information, thanks!