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Author Topic: 2.5 V6 - Juddering and poor MPG  (Read 3364 times)

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2am Omega

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #15 on: 15 March 2009, 23:45:31 »

Just back from hospital .. long day .. exhausted, so will post more tomorrow.

Many thanks, Chris, for having a look at my 97R 2.5 Elite saloon today.

Unfortunately changing the plugs has made no difference to the juddering lumpiness (most noticeable as soon as the auto box changes into top gear at 2000rpm at 50mph) and the poor mpg (typically high teens and just over 20mpg on a run) even with my gentle driving style.

Something has happened to change it suddenly (after the MOT) from the former smooth velvet V6 doing 28-35mpg to the more sluggish, less responsive and sometimes juddering fuel-hungry car of today. Paperclip test shows no fault codes.

Any suggestions please?

Could this be a fuel jets or filter issue?
« Last Edit: 16 March 2009, 00:24:19 by 2am »
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Kevin Wood

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #16 on: 16 March 2009, 13:58:12 »

If the SAI hoses have failed and the rear silencer has shed packing material are you sure there's no blockage in the exhaust system?

Might be worth checking that the ignition leads all go to the right terminal posts on the DIS pack if someone has attempted a plug change. I'd be inclined to treat it to a new set of leads if they have started to deteriorate. It's only a matter of time before they let you down but worth doing the cam cover gaskets if there is leakage, otherwise the new leads will go the same way.

I would also repair or at least block the vacuum leaks. You won't have a lot of air leaking into the system but might as well eliminate that as a cause.

Kevin
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2am Omega

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #17 on: 16 March 2009, 18:06:02 »

Thanks Kevin ..

Chrisgixer checked and photographed the exhaust yesterday. There seems to be good pressure at the tail pipe. It is intact externally and does not seem to be blocked. He shone a torch right through inside the rear box, which has shed its innerds, but otherwise seems ok.

He changed all the spark plugs but sadly there was no improvement. Worryingly he found an apparently clean-cut chunk of rubber from the plug cap of pot 6 .. see his photo posted last night. MOT repairs Sabotage?

I have previously made brief reference to this. I will post a separate new thread about my concerns from my recent MOT and repairs, which was immediately before my car problems started.

Could someone please explain the car's vacuum system, how critical or sensitive it is, and what the "multi-rams" do.

And Chris, could you please let me have contact details for the HT leads.







« Last Edit: 16 March 2009, 18:21:23 by 2am »
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mantagte

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #18 on: 16 March 2009, 18:24:37 »

sounds like how mine went when the dis pack failed
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2am Omega

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #19 on: 16 March 2009, 19:00:26 »

Thanks Mantagte .. could you please describe your car's symptoms to give a bit of detail for comparison with mine.

Mine is very significantly worse, juddering, just after the auto changes into top gear at 2000rpm at 50mph .. then it smooths out above 60mph, but still not as velvety smooth as it used to be.
« Last Edit: 16 March 2009, 19:01:06 by 2am »
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mantagte

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #20 on: 16 March 2009, 19:18:32 »

not smooth on tick over as it should be enginge vibtrating from side to side
if i held it in gears (mines auto) it seemed to smooth out a bit as you got higher up the rev range and the faster i went it seemed to get better but as i slowed down i could feel it was lumpy still
very rotten egg smell from the exhaust on 2-3000 revs
changed plugs made no difference
changed leads made no difference
swore
took of dis pack
found a spilt a half way round the bottom and could see rusty metal inside
bought new dis pack from ebay
perfect loverly and smooth again
hope some of this helps
and yes i know i rabbit on ;D
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2am Omega

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #21 on: 16 March 2009, 19:33:47 »

mmm .. interesting but ..

- my engine is not physically vibrating or jumping about at all.
- I'm not aware of a rotten egg smell from my exhaust at any revs  - maybe your diet?  ;)

Yes mine is uneven at tickover, causing computer display to flicker slightly.

My fuel consumption is increased by about 40% .. what about yours?
« Last Edit: 16 March 2009, 19:35:30 by 2am »
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Varche

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #22 on: 16 March 2009, 19:34:45 »

I'll second that. My same car as you developed the same symptoms. It seemed fine pootling around but on the open road when it got to about 50 and changed into top then along came the juddering - particularly on a light throttle. Change down and press accelerator gave more power and masked the misfire a bit.

I too changed plugs. No change
Then changed plug leads No change.
Then changed DIS Pack BINGO cured.

My money is still on DIS pack but as others say you have to try the other stuff first.

Varche



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mantagte

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #23 on: 16 March 2009, 19:39:02 »

My fuel consumption is increased by about 40% .. what about yours?

yes my fuel cosumption went up i was loosing about 7 mpg
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Marks DTM Calib

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #24 on: 16 March 2009, 19:41:08 »

If its not smooth on idle then its less likely to be a blocked exhaust (not much gas produced on idle)

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2am Omega

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #25 on: 16 March 2009, 19:50:45 »

and the only way forward is trial and error .. buy and fit the replacement HT leads and Dis Pack just to see if the problem is cured? No means of testing?

I love my Omega but there has to be a limit on expenditure on a car worth just a few hundred pounds  :(
« Last Edit: 16 March 2009, 19:53:38 by 2am »
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mantagte

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #26 on: 16 March 2009, 19:54:38 »

speak to one of the breakers on here someone may have what you need cheapish
cheaper than ebay anyway
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feeutfo

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #27 on: 16 March 2009, 22:09:04 »

the Exhaust back box has nothing in it. The entry pipe can clearly be seen when looking in the exit pipe with a torch. Baffle edges and rust clearly visible. But the baffle edges seemed at odd angles.
Arvin meritor stickers no the back box and centre sections, so not gm from cat back. If the rear box has fallen apart then is it possible the centre section has done the same? Trouble is from what i saw in the back box, it left me with a mental image of somebody ramming a metal bar up the tail pipe.
I think its worth further investigation at the very least. Something is not right with all this.
 
Ill leave that for another thread. Mean time the poor running, i can not understand personally why the engine is not leaping about? The dis looked ok from the top but thats no proof the under side is the same, 2am has had the car 4 years so dont think anybody has changed the leads.

Thanks for other opinions,

Will re send details for leads, first text was a picture message. Maybe didnt come through. Cheers.
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2am Omega

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #28 on: 16 March 2009, 22:54:04 »

Chris, Thanks for the text with contact details for HT leads and Dis Pack. I will follow that up tomorrow.

You say I also need "the vac tank on the intakes" .. please explain so that I understand what I am asking for.

I did not get a photo text. Could you please post on here .. mine is just a mobile phone, without photo facility.

Quote
But the baffle edges seemed at odd angles .. Trouble is from what i saw in the back box, it left me with a mental image of somebody ramming a metal bar up the tail pipe.
I think its worth further investigation at the very least. Something is not right with all this.

That REALLY worries me .. and it reinforces my fears about that MOT garage after I queried their charges for "repairs". My Omega was a velvet smooth beauty before that MOT .. these problems of juddering running, poor MPG, and the exhaust spewing its contents, they ALL started on the first journey after I collected the "repaired" car from that MOT garage.

Add to that the other things you found yesterday .. the clean-cut chunk of rubber from the plug cap .. and the botched shock they fitted on one side, fudging the self-levelling suspension .. and it adds up to VERY GREAT CONCERN.

What do you think I should do?




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lpgelite

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Re: 2.5 V6 - Juddering and poor MPG
« Reply #29 on: 16 March 2009, 23:02:47 »

HT leads are arranged in pairs on the DIS pack. Can't visualise the numbering sequence off hand, but if someone with a spare DIS pack can take a look to see if 1and 5 are a pair then I think you've found your problem. Use a 1999 model year DIS pack for best results. There won't be any obvious signs of failure as the fault occurs internally (usually insulation breakdown).

Your HT leads look shot and it would be well worth replacing them. Also check to see if you've got platinum tipped plugs. These place a huge strain on the HT system and I would recommend using only copper cored NGK (BKR6EK) or Vauxhall's own brand plugs in this engine.
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