Astra 1.4i Missfiring on idle only

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Fri 13 Jun 2003 20:51
Astra 1.4i Missfiring on idle only - Philflies
Vauxhall Astra 1.4i 1997 P-reg.
It's basically misfiring on idle and the revs are wandering up and down too.
There's no other problems at all whilst driving or giving it any amount of throttle, infact the engine is running very smooth (it's only done 41,000).

On a cold startup it's less of a problem as the choke (auto) keeps the revs slightly higher than the normal warm idle.

I've taken it to two garages and they swear blind there's not a problem! You can see/feel/hear the problem! The engine misfire's about every 2 seconds or so then the revs drop right down and then increase again briefly.

Any idea's advice welcome

Thanks

Phil
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Fri 13 Jun 2003 21:58
Astra 1.4i Missfiring on idle only - David Davies
This may be some sort of sticking valve or lifter problem.Try giving it an engine flush and new oil and filter and use high grade oil.If you let it idle for a few minutes and then switch off you should be able to identify which cylinder is misfiring by examination of the spark plugs,one will be a different colour to the other three.
David Davies (Tune-Up Raglan)
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Wed 25 Jun 2003 13:04
Astra 1.4i Missfiring on idle only - Philflies
Hi David, thanks for the advice (sorry for the long delay to reply). I\'ll give looking at the sparks a go. It\'s just been serviced and had a new filter and oil and new sparks. It was doing it before the service but there\'s no real change after the service. I\'ve also used a fuel injector cleaner too. There\'s been no difference.
I daren\'t take it to Vauxhall as it comes out with a different problem everytime I take it to them.
(dealers name deleted, if anyone\'s interested)####

Someone suggested it could be the ECU? Could it?
It\'s only on the idle which is really strange, it purrs along at any other time.

Any advice always welcome.

#### No naming and shaming, thankyou. DD.
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Wed 25 Jun 2003 15:34
Astra 1.4i Missfiring on idle only - Andrew Moorey (Tune-Up)
You seem to have got the cutting out problem licked from your earlier post, What was it?
The problem you have now points to an air leak around the inlet manifold. Favourite is the gasket under the throttle body. This will also upset the Lambda sensor which will try and correct it. Possibility also that the Lambda sensor may be getting lazy and switching too slowly.
Andrew


Simplicate and add lightness!
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Wed 25 Jun 2003 23:21
Astra 1.4i Missfiring on idle only - David_S
I would also look at the Throttle Body and give it a clean if it is showing signs of being gunked up. Is there an idle stepper motor on these? I know that the Vectra can have a problem where the the mechanism gets a bit stuck which could cause the idle to hunt or misfire

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Wed 25 Jun 2003 23:09
Astra 1.4i Missfiring on idle only - geoff C
These symptoms are nearly always caused by an air leak. The most likely leak is in the hose which runs from the cam housing to the inlet manifold. This may be split at the cam housing end where it gets particlarly oily. There are a lot of vacuum hoses connected to the inlet manifold, some via the brake servo vacuum pipe, any one of these leaking may cause this problem.
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Thu 26 Jun 2003 06:37
Astra 1.4i Missfiring on idle only - greaser pv
I'd go with the air-leak theory too.There is a black ( vacuum-operated ) valve located at the back of the engine under a black cover, this can fall apart, click it back together. Let us know the out-come.
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