Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: mikeh on 26 August 2010, 19:06:16

Title: Lumpy idle and acceleration
Post by: mikeh on 26 August 2010, 19:06:16
Girlfriend was out in the Omega last night in the rain and floods and the car started to misbehave. It was struggling to go over 50mph and 2000rpm and smelling a bit eggy on the motorway, so the RAC recovered it home.
I had a look at it today and no fault codes stored, just
12 & 31 with ignition and 12 when running.
Idle is slightly less that usual, but seems to rev ok in park, but is very hesitant when driving. Will get up to 70 eventually and run ok but you have to do it slowly.
Kick down causes hesitation and clunky gear change.
Any suggestions on what might be the problem or other checks I can make.
Thanks, mikeh.
Title: Re: Lumpy idle and acceleration
Post by: Welung666 on 26 August 2010, 19:08:11
Check under the passenger side skuttle to see if the padding is wet. If it is check the rear plug well that side for water. If it's dry then it might well be the dis-pack failing.
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 26 August 2010, 19:34:52
Wellung666, thanks for the reply.
I checked under passenger skuttle and it was fairy dry and clean. Took out the  pollen filter and that was also dry, and poured some water in and it drained out straight away. Whereabouts is this padding?
The drain grommet on the drivers side was also clear.
Thanks, mikeh
Title: Re: Lumpy idle and acceleration
Post by: Welung666 on 26 August 2010, 19:45:22
Go from the top of the plenum back towards the windscreen and feel the padding on the top of the bulkhead behind the plenum.
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 26 August 2010, 21:27:28
I can see some rain water dripping from under the skuttle near the dis /bulkhead area. Must be getting in where windscreen meets skuttle. Assuming its a wet dis causing the problem will it improve as it dries out or would you think new one required. Are these dealer only or are ebay ones ok?
Thanks, mikeh.
Title: Re: Lumpy idle and acceleration
Post by: Welung666 on 27 August 2010, 01:20:05
First things first! Get the car somewhere dry, run a bead of sealant between the 2 halves of the skuttle once it is bone dry. That should stop most of the water running in. The problem with the dis-pack is that water will get between the plates and corrode it. 99% chance you will end up replacing it now anyway.
Title: Re: Lumpy idle and acceleration
Post by: TestOmega on 27 August 2010, 03:13:33
Quote
I can see some rain water dripping from under the skuttle near the dis /bulkhead area. Must be getting in where windscreen meets skuttle. Assuming its a wet dis causing the problem will it improve as it dries out or would you think new one required. Are these dealer only or are ebay ones ok?
Thanks, mikeh.
I have used dielectric clear rubbery sealent to great advantage in my Catera while seating the coil pack.  Had exactly the same problem and never again.

All h*ll breaks loose in heavy rain and the scuttle stuff can only do so much.  There are splashes up and down with the fans going, which do dry up fast in the hotter areas.

Good luck.   ;)
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 27 August 2010, 11:40:20
Omega now in garage (dry). I'll strip off all the plastic skuttle and trim from the windscreen so I can clearly see how wet it is back there.
Title: Re: Lumpy idle and acceleration
Post by: amba on 27 August 2010, 12:01:04
Found same problem with mine.
Water would run off screen and then where the 2 parts of the scuttle join the foam wasn,t making water seal and back plug well and top of cam cover wet.
I removed both sections of the scuttle panle.Gave it a thorough clean and dry ,then ran a thick bead of silkaflex black selant across the metal curved section of the bulk head the pushed the scuttle down into it to seal,then another bead across the point where both parts overlap and have not had any problems since.
Get it down sooner than later and you may not end up needing to replace dispack,depending how long it has been seaping through.
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 27 August 2010, 18:17:13
Skuttle off and its all dry back there, but then it has been in the garage for 24 hrs and I let it idle until the fan kicked in.
I changed all 6 plugs, mainly to have a look at the condition of the old ones and to see how much oil, if any, was down there. Plugs and holes all looked ok.
Just been for another test drive and it is lacking power and stinks of rotten eggs.
I ran it in the garage in the dark last night at idle and about 5000 rpm and did'nt see any sparking/arcing.
Is the next thing to replace the dis pack?
Thanks, mikeh.
Title: Re: Lumpy idle and acceleration
Post by: PhilRich on 27 August 2010, 18:43:39
Unplug the MAF & see if there is any improvement. :-/
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 27 August 2010, 19:39:40
Ok, drove round block with maf unplugged. Exactly the same apart from engine light on. Is there anything else I can check before trying to remove the dis pack?
Thanks, mikeh.
Title: Re: Lumpy idle and acceleration
Post by: Kneepad on 27 August 2010, 20:08:12
Quote
Skuttle off and its all dry back there, but then it has been in the garage for 24 hrs and I let it idle until the fan kicked in.
I changed all 6 plugs, mainly to have a look at the condition of the old ones and to see how much oil, if any, was down there. Plugs and holes all looked ok.
Just been for another test drive and it is lacking power and stinks of rotten eggs.
I ran it in the garage in the dark last night at idle and about 5000 rpm and did'nt see any sparking/arcing.
Is the next thing to replace the dis pack?
Thanks, mikeh.

Would this not point to the cat.  :-/
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 27 August 2010, 20:37:39
I think the 'egg' smell is unburnt fuel in the cat.
Big question is what is causing the unburnt fuel.
Title: Re: Lumpy idle and acceleration
Post by: Kneepad on 27 August 2010, 21:12:30


Take it back into your garage. Open the bonnet and start the engine. Then put the garage lights off and see if there are any stray sparks from plugs, leads.
Title: Re: Lumpy idle and acceleration
Post by: Broomies Mate on 27 August 2010, 21:25:10
Unbelievably, I have just logged onto the forum to start a thread, which, word for word would have been identical to the OP's.... with the exception my Girlfriend is too scared to drive the Omega  ;D

Massive smell from the CAT and running on 5 cylinders unless above 3.5/4k when all seem to kick in.

How much is a new Dis-Pack from Vauxhall?  Can you buy them anywhere else, and if so, is the saving worth it?  :y
Title: Re: Lumpy idle and acceleration
Post by: skyblue on 27 August 2010, 21:40:47
about £170.00 quidfrom a dealer but  have seen genuine  ones of ebay for about 85quid ... pat ones from about 33quid
Title: Re: Lumpy idle and acceleration
Post by: amba on 27 August 2010, 21:54:55
Are you sure you are getting a good spark at each plug.?

It can be difficult to check but I found the use of a plug light flasher does the job and confirms the presence of a spark.

Normally when dispack starts to die it affects 2 plugs as they are linked.

Rotten egg smell is unburnt fuel which points to it not firing..would advise not driving to much as you will end up killing the catalytic converter which will cost more.
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 27 August 2010, 22:03:48
Kneepad, tried that last night and no stray sparks.
Amba06128, no, I'm not sure if getting a good spark at each plug but I would guess not. Is a plug light flasher one of those things that connects to the ht lead?
Title: Re: Lumpy idle and acceleration
Post by: Broomies Mate on 27 August 2010, 22:04:03
Cheers.  I only had to drive 6 miles home after it started playing up.

"My Naff Code Reader" says the three 'output tests' for cylinders are firing correclty, but evidently they are not.

The EML flashed a couple of times under heavy acceleration just before the problem started, but not long enough to store a code. :(
Title: Re: Lumpy idle and acceleration
Post by: amba on 27 August 2010, 22:17:00
You won,t get  stored code from anything at fault on the HT side.

Plug spark checkers are just fitted onto the top of the plug and other end into ht lead.Not very technical but atleast they will prove if each lead is providing a charge to give a spark..then you can rule out the dispack and each lead...it then will point to the plug..but it will be a process of elimination.
Title: Re: Lumpy idle and acceleration
Post by: CaptainZok on 27 August 2010, 22:42:33
Proper way to check the dis is to fire it using tech2 with a test plug connected. That way you can see the spark.
Title: Re: Lumpy idle and acceleration
Post by: Welung666 on 27 August 2010, 22:46:25
Quote
Proper way to check the dis is to fire it using tech2 with a test plug connected. That way you can see the spark.

... and the poor mans way is to take the boot off, take the spring off, re-fit the boot and pop the dis pack back in. Do each pot in turn and listen to when it's no different than the 'normal' rough running ;)
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 28 August 2010, 10:30:36
Thanks for all the helpful replies.
I'm going to remove the dis pack and if its anything like the pic in the maintenance section then get a new one.
Does anyone have any experience of the ebay pattern ones?
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 28 August 2010, 20:55:49
Old dis pack finally removed and fortunately it looks exactly like the picture in the maintenance guide - rusted and cracked. So that hopefully will be the cause of all the rough running.
Thanks for all your help.
Title: Re: Lumpy idle and acceleration
Post by: mikeh on 06 September 2010, 18:58:44
New bosch dis unit from vauxcentre fitted and now all ok.
Thanks for all your help.
Title: Re: Lumpy idle and acceleration
Post by: Kneepad on 06 September 2010, 19:47:12


Job well done.   :y
Title: Re: Lumpy idle and acceleration
Post by: Knight3179 on 06 September 2010, 20:16:54
Hooray, now come sort mine it does the same thing  :D ;D