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Any thoughts on Astra issue?

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JamesV6CDX:
Firstly, when using light throttle to maintain a steady speed, it will somtimes lurch, and "kangaroo" despite a steady foot.

Secondly, there is an intermittent acceleration problem on LPG.

When I first bought it, it would not accelerate well on LPG - the power was coming in "surges".

I replaced the plugs, and instantly it was much much much better.

But now, the surging while accelerating is back intermittently (although nowhere near as bad as before).

The evaporator is red hot, no smell of LPG, filter recently changed, and no fault codes.

I am beginning to think that maybe the coil pack is a little tired - hence OK on petrol, and intermittent on gas?

The only other observation is that this car seems to have 2 lambdas. One in the top of the manifold - and another behind the exhaust flex joint.

The exhaust flex join has a SMALL blow which I've just noticed - I wonder if this is potentially confusing lambda readings and causing the problems?

It is very small though.

The problem is much more noticable on LPG, not really apparent on petrol.

I don't think it's a LPG system fault though - I think it's an engine issue, which is just being shown because LPG places higher demands on ignition components etc....

Any thoughts most welcome :y

JamesV6CDX:
Think I may have narrowed it down

Getting a "pop, pop" noise occasionally from the exhaust at idle. Worse on LPG, but exists on both fuels.

Plug number 3 - half of it is black. There is good compresson on this cylinder, so I reckon the coil pack is not firing this one properly....

I have ordered a new one from Vauxhall whatsit on egay - only £40, hopefully it will do the biz.

Oh, and as soon as all the firearms officers blocking our road clear off and let me through ::) I will go to VX and get some new GM plugs!

Kevin Wood:
Post-cat lambda sensor will at worst put the emissions light on.

IME a weak spark will cause a misfire at low to mid RPM under heavy load. At idle the puniest spark will be fine. Any codes stored? Just wondering if it's running a little lean due to a metering problem or air leak?

Kevin

JamesV6CDX:

--- Quote ---
IME a weak spark will cause a misfire at low to mid RPM under heavy load. At idle the puniest spark will be fine.


--- End quote ---

And that's exactly the symptom.

Combined with number 3 plug becoming black in next to no time, I think that cylinder's not firing efficiently, and leaving unburnt fuel.

With any luck the new coil pack will sort.  :y

Marks DTM Calib:
What engine is in the Astra?

The coil per plug setups will detect the missfire and shut the injector off.

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