If you have to replace parts, try www.autovaux.co.uk
Also Vauxhall's *own brand* sparkplugs aren't that expensive, and probably even cheaper from autovaux as well. If you know someone with a Vauxhall Trade Club card, then the parts from Vauxhall themselves will be even cheaper.
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I'm not sure which ECU is used in the Omega but in a '98 model I would expect a misfire to cause the Service light to illuminate.
Possibly - but misfire detection algorithms tend to have their sensitivity reduced somewhat to prevent false detections, which means that sometimes obvious misfires aren't picked up.
>>The knock sensor should detect pre-ignition...
I don't think so. A misfire is no ignition, so the knock sensor "hears" nothing, just like during a normal burn.
and the emmissions sensors should notice unburnt fuel being dumped into the exhausts.
Again, I don't think so. The sensor in the exhaust can't measure unburnt fuel, it just looks for oxygen.
If I were looking at the car, I would be paying close attention to the HT system - as Aprilia says.
Only if I found nothing wrong there might I consider reading the ECU for codes.
Number_Cruncher
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I'd say HT leads, coil pack or plugs, in diminishing order. I know all three are a real pain to change on a miggy V6, been there, done that, got the grated knuckles ;-(.
I now only buy 4 cylinder Omegas.:-/
In general I'd use autovaux, as DD suggests, although the last set of HT leads I bought from them for a 4 cylider miggy only lasted 30K before playing up when hot. On the other hand the last plugs I bought from them appeared to be genuine Vx and were a mere 2.50 each, for the 4 electrode ones.
From memory there are very few, if any, fault codes related to HT issues, so I think this helps point to HT as the problem.
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I had the original HT leads changed as a precaution on my (ex) 3.0V6 Omega Elite when I acquired it (around 90k). I sourced them from Autovaux (link provided by DD above) and they were about £70 from what I recall. They were original GM parts that the Vx dealers were selling for over £150 at the time! Also the original GM plugs were only about £2-3 each from Autovaux.
It's now almost 2 years since I sold it and I still often regret that decision. IMO as a model, the Omega may have had more than it's fair share of faults and niggles but as a VFM, "do-it-all" car it was hard to beat, especially in 3.0V6 elite/MV6 spec.
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Problem solved, and most of you were on the money.
Removed one plug (left bank, middle) and there is no electrode in it, and some of the ceramic is missing too.
I guess these are rattling round in the cylinder now...
Anyway, a temporary plug has cured the misfire, and I have just bought a 6 pack from GM for about £21, for fitting at the weekend (although the rear two are hard to access).
Checked invoices, the current plugs aren't much over 40k old, which is their expected lifespan, so they were due a change anyway...
Removal of the plug also showed up oil around the plugs so that will need attention in due course (it isn't losing much). I hope that's something simple (= cheap)!
Thanks all.
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40K on one set of plugs!!!!!!!!!!!!!!!!!
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40K on one set of plugs!!!!!!!!!!!!!!!!!
Erm....yes, that is the recommended changing interval for plugs on these - and pretty much every other car I've owned for that matter.
Incidentally Smokie I had the cam cover gaskets changed by a Vx dealer just before I got rid of my V6 ( not my idea), just about got change from 200 quid. As usual the parts are expensive from Vx, IIRC about 65 quid per side for new cam cover & gasket. Autovaux are your friend.
I'd check the breathers while you're at it, the gaskets start leaking because a) the carpy cam covers are plastic & warp & b) pressure builds up in the covers when the breathers get blocked, hence the oil gets pushed into the spark plug wells.
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> 40K on one set of plugs!!!!!!!!!!!!!!!!!
New plugs, particularly the Bosch platinums, last much longer nowadays thanks to modern engine control systems.
Plug changes on the XJ are at 70K intervals.
Plug changes on the Chevy V8s are at 100K intervals. A good thing considering how difficult they are to get to on mine.
Kevin...
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Smokie,
The Omega how2 section over on cavweb will probably benefit you.
www.cavweb-forums.co.uk/forumdisplay.php?f=82
Particulary,
Spark Plug change:-
www.cavweb-forums.co.uk/showthread.php?t=77866
Rocker box gasket change (as you've got an oil bath around the spark plugs:-
www.cavweb-forums.co.uk/showthread.php?t=63628
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NC,
You seem to have misconstrued my post.
I'm not sure which ECU is used in the Omega but in a '98 model I would expect a misfire to cause the Service light to illuminate.
>Possibly - but misfire detection algorithms tend to have their sensitivity reduced somewhat >to prevent false detections, which means that sometimes obvious misfires aren't picked up.
Misfire detection is much better now than it was in '98 which is why I asked if it was a "hard (permanent) misfire".
>>The knock sensor should detect pre-ignition...
>I don't think so. A misfire is no ignition, so the knock sensor "hears" nothing, just like >during a normal burn.
Read that again. I said "pre-ignition" not misfire.
and the emmissions sensors should notice unburnt fuel being dumped into the exhausts.
>Again, I don't think so. The sensor in the exhaust can't measure unburnt fuel, it just >looks for oxygen.
Excessive amounts of unburnt fuel in the exhaust causes the sensor to become sluggish. This, in turn, can cause the ECU to lose control of the mixture resulting in over-rich or over-lean running. An OBD II compliant system is supposed to recognise this condition, go open loop and log a P01XX fault code. The 'XX' is the location code for the sensor. If the ECU does not go open loop then you can get an "over-lean misfire".
>If I were looking at the car, I would be paying close attention to the HT system - as >Aprilia says.
>Only if I found nothing wrong there might I consider reading the ECU for codes.
madf and Aprilia had already suggested the usual suspects. My post was a request for more information about the symptoms.
Kevin...
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Hi Kevin,
>>You seem to have misconstrued my post.
You're probably right - I suspect if were speaking face to face it would all be much clearer.
Cheers,
Number_Cruncher
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>I suspect if were speaking face to face it would all be much clearer.
No problem. English is not my first language ;-)
Kevin...
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