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[Jim Bob2]

My omega made a big pop last week and fired a load of crap out of the exhaust. Its been running fine up until just now. Its started missing, down to 3 or 4 cylinders at low revs seems to fire on 5 and maybe 6 at high revs. It also stinks of rotten eggs.
No EML light showing.
What do you recon guys???

[Dave-C]

Sounds like a blown cat to me!!  Poss due to an oxygen sensor failing, overfueling and igniting... Also poss DIS pack partial fail too!!

DC

[Jim Bob2]

Thanks for the advice Dave. Just tried it again and its worse now.
Missing even more. Could this be due to bad fuel? I always fill up at Asda.

Sounds like a blown cat to me!!  Poss due to an oxygen sensor failing, overfueling and igniting... Also poss DIS pack partial fail too!!

DC

[Dave-C]

Would say unlikely to Asda petrol, scare now over...........  has the car got very wet lately, poss poor connection on an O2 sensor..

Had loads of rain up here in the Midlands.......

DC

[Jim Bob2]

No connections look ok. If i change the o2 sensors will it run ok with a nackered cat? Its got 6 months mot to run so I'll probably sell it if I can get it to run ok again(not to anyone on here of course).

Would say unlikely to Asda petrol, scare now over...........  has the car got very wet lately, poss poor connection on an O2 sensor..

Had loads of rain up here in the Midlands.......

DC

[Dave-C]

No connections look ok. If i change the o2 sensors will it run ok with a nackered cat? Its got 6 months mot to run so I'll probably sell it if I can get it to run ok again(not to anyone on here of course).

Would say unlikely to Asda petrol, scare now over...........  has the car got very wet lately, poss poor connection on an O2 sensor..

Had loads of rain up here in the Midlands.......

DC

Don't give up that easily!!!!!!!!  Someone on here WILL have the answer...  Keep this post up to date on whatever you try...  At a push, remove the cat / cats, break up the honeycomb shake it out (You'll need a dust mask) refit n' will run OK'ish, loss of back pressure on engine may cause a problem or two..... If o2 sensor is u/s always try a scrap one...  can be measured for OK with a multitester....

DC

[Kevin Wood]

Doesl the EML come on with ignition?

It's odd that it would throw its' toys out of the pram in such big style with no fault codes.

Could be that a cat or the exhaust is blocked though. Might be worth getting under it as the exhausts warm up and see if one of the pipes stays cool.

It'll probably run OK with a bad cat, as long as it'll flow exhaust gases. (until MOT time, of course)

Kevin

[Jim Bob2]

The EML light goes out once car starts. Any ideas how much an o2 sensor will cost trade club ?

Doesl the EML come on with ignition?

It's odd that it would throw its' toys out of the pram in such big style with no fault codes.

Could be that a cat or the exhaust is blocked though. Might be worth getting under it as the exhausts warm up and see if one of the pipes stays cool.

It'll probably run OK with a bad cat, as long as it'll flow exhaust gases. (until MOT time, of course)

Kevin

[Kevin Wood]

I'm not convinced the oxygen sensor should be your first port of call. If that were reading bad, it would run reasonably well but light the EML.

Oxyneg sensors are not active until the engine is warm anyway.

I think a check of the exhaust system for blockages should be at the top if the list.

Kevin

[Jim Bob2]

Thanks Kevin. I may have a go at that tommorrow. Not looking foward to it. I have a funny feeling you are right though. One of the cylinders on each bank is'nt fireing at all though. I tested all 6 cylinders by removing one plug lead at a time. Could that point to the o2 sensor ?

I'm not convinced the oxygen sensor should be your first port of call. If that were reading bad, it would run reasonably well but light the EML.

Oxyneg sensors are not active until the engine is warm anyway.

I think a check of the exhaust system for blockages should be at the top if the list.

Kevin

[x25xe]

Which cylinder number is not firing on each bank?  If there was no difference when you removed the leads, I would suspect the DIS pack - seems as though one of the coils which provides a spark for 2 cylinders has failed.  

This would also support the earlier post about the cats breaking down due to unburned fuel.

These symptoms would be nothing to do with the o2 sensors.

[Kevin Wood]

I agree. Each coil within the DIS pack fires two plugs so I'd say try a good DIS pack first and see what that does.

If you're lucky the cats will have survived. The unburnt fuel would explain the bad smells as the cats try to burn off the excess.

Kevin

[Jim Bob2]

There was certainly no spark from the plug nearest the front of the car on the left bank of the engine( when standing at front). To double check I took the plug out and plugged the lead back on and started the engine.No spark. I had more problems checking the other bank due to access. I just tried it again (cold engine) and it only just runs now. Only fireing on 3 or 4 cylinders I recon. Its been a rapid deterioation. From running fine to hardly running at all within 10 minuites of running. Would the dis pack do this ?.Also I've had no misfireing before to cause unburnt fuel to build up.I drove a 200 mile trip on saturday virtual non stop with no problems at all.

Which cylinder number is not firing on each bank?  If there was no difference when you removed the leads, I would suspect the DIS pack - seems as though one of the coils which provides a spark for 2 cylinders has failed.  

This would also support the earlier post about the cats breaking down due to unburned fuel.

These symptoms would be nothing to do with the o2 sensors.

[Kevin Wood]

There was certainly no spark from the plug nearest the front of the car on the left bank of the engine

That cylinder should be paired with the centre cylinder on the right bank I think.

Either way, if there's no spark at all I'd still suspect the DIS pack. Might be worth changing the plug leads too, just in case.

You could try removing the DIS pack and measuring the resistance of each winding to see if they are intact and of similar resistance if you don't want to shell out for a new one without further confirmation.

Not had a HBV or cam cover seal failure recently?

Kevin

[Jim Bob2]

Yes. I did the HBV valve 6 months ago. Has the antifreeze buggered it up?

There was certainly no spark from the plug nearest the front of the car on the left bank of the engine

That cylinder should be paired with the centre cylinder on the right bank I think.

Either way, if there's no spark at all I'd still suspect the DIS pack. Might be worth changing the plug leads too, just in case.

You could try removing the DIS pack and measuring the resistance of each winding to see if they are intact and of similar resistance if you don't want to shell out for a new one without further confirmation.

Not had a HBV or cam cover seal failure recently?

Kevin