Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: omega si on 07 December 2006, 22:56:57
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Right here goes!
engine has got an intermittent misfire. most of the time its fine, other times its maybe got a slight miss on tickover but noticably so when revved up.
The story so far is that I recently replaced a knock sensor (drivers side) where the wire had got squashed. E/m light on and all that. Note though that it still had the occasional miss before i did the knock sensor. thought it might be due to the air mass sensor, so i got a second hand one off ebay as it was going cheap (thought it wouldnt harm to have a spare either way) but changing it has made no difference.
The car has had the dis pack, leads and plugs done May 2005.
Its a real pain to diagnose tho, no e/m light and only comes on for a bit (usualy when im at work and the wifes using it).
I was planning on checking the induction system for leaks, then pop the plenum chamber off and check sparks. Anyone got any ideas if this is the best plan or where i should start my investigation??
Cheers
Si
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Welcome to the forum omega si.
Which engine (2.0-8/2.0-16/2.2/2.2DTI/2.5/2.5TD/2.6/3.0/3.2/), year, and mileage....?
Did you check for engine error codes?
Missfire can occur for many reasons, DIS ot HT could have gone again, leaking rocer cover gaskets can flood the plug wells, leaking or disconnected vacum pipe, clogged fuel filter, injector problems, and more...
Either way don't drive the car with a missfire, the cats don't like raw fuel!
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Also - if EML came on, check for error codes before doing anything else.
Do not check for spark - this is seriously high voltage, not like the old days where you could simply hold the HT lead away from the plug...
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Error codes have been checked.
Had shown a low voltage on the air mass sensor but wasnt present at the time, and it only happened once.
By the way its a petrol 2.5 v6 petrol auto and done 92k.
Fired it up tonight and its purring away nicely.
Gonna test the ht by removing the fuel injector multi plug, pulling a lead off one plug at a time and then using a spare plug, check for a spark holding it a few mm away from the block (with insulated pliers) Should be okay doing this right?
Also, had the near side rocker gasket leak last year some time after the dis pack was replaced. But sorted it and all was fine until now. Its all dry as a bone up there at the mo.
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Gonna test the ht by removing the fuel injector multi plug, pulling a lead off one plug at a time and then using a spare plug, check for a spark holding it a few mm away from the block (with insulated pliers) Should be okay doing this right?
DONT DO IT - PLEASE.
For Two reasons.
1) Modern engine management systems carry VERY high current through the ignition leads, I had such a hell of a belt off an omega doing this, and I had rubber gloves on!! Learn from my experience, - bad move.
2) It will easily goose the DIS pack by getting it to spark when the plugs not installed into the car.
Please trust me on this one mate.
You say you had ONE rocker cover gasket done? Why only one? I would have thought it was only good practice to do both, if you're going to go to the trouble of getting the pleunum/trumpet off to do one.
Although you had the gasket done, did you have the FULL breather system cleaned? And did you use a genuine VX gasket? Both very important points. If breathers were not cleaned, it could easily have blown again.
Unfortunately you need to go back to basics before looking too far. I would recommend starting with a cold engine, and removing each plug lead one by one, checking the condition and cleanliness of the contacts. Make sure there is no oil in ALL of the plug holes.
Then look at the condition of the plugs.
From experience, I reckon you will find a lead that's split somewhere. On mine, it was Cyl 6. It was split up the shank of the lead, and caused me an intermittent miss, Just like you describe!!
Tip = if checking for spark, I attach a timing gun to the lead in question to see if it's firing. you won't be able to see anything re. the ignition timing this way, but you WILL See a spark.
Where are you located? If yu're local I can lend a pair of hands to do this.
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Where are you located? If yu're local I can lend a pair of hands to do this.
Thanks for the offer mate , but I'm in Leeds. Probably a bit too far for you.
Can you explain more regarding the breathers as I'm not sure what you mean here?
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Hi Si and welcome :y
For cleaning the breathers try this
http://www.omegaowners.com/forum/YaBB.pl?num=1152598350 :y
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Hi Si and welcome :y
For cleaning the breathers try this
http://www.omegaowners.com/forum/YaBB.pl?num=1152598350 :y
Cheers Pete
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Couple of general (very general) pointers on v6 misfires:
Read codes, and fix any codes present.
Codes relating to MAF are frequently an air leak or egr problem.
No codes is often an HT problem.
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Thanks for that. Is there anything I should be looking out for with the egr valve?
Just started stripping a few bits off ready for tomorrow and found oily deposits in the air pipe between the large induction pipe attached to the throttle body and the idle air control valve.
Is this normal? Is this related to cleaning out the breathers?
Cheers
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Thanks for that. Is there anything I should be looking out for with the egr valve?
Just started stripping a few bits off ready for tomorrow and found oily deposits in the air pipe between the large induction pipe attached to the throttle body and the idle air control valve.
Is this normal? Is this related to cleaning out the breathers?
Cheers
Sounds like throttle body, as well as breathers, could do with a bit of a clean...
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the crud in the pipes is normal, its just a build up over time. My 2.2 was almost completely blocked, cleaning it out gave a noticeable MPG and performance increase.
Might also be worth checking the leads, and check all the connections on the DIS Pack are good.
Has the engine ever had an oil cooler fail or any other problems before this misfire appeared?
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Has the engine ever had an oil cooler fail or any other problems before this misfire appeared?
No, nothing like that. It started playing up around the same time as the drivers side knock sensor but I dont think that should affect anything should it?
Cheers
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Just an update for anyone else having similar problems.
Rocker gasket on drivers side needed replacing, plugs were soaked in oil.
That done I removed the leads and dis pack. Dis pack seems to be the problem, or at least one of them! No6 terminal is badly corroded (all the rest look like new!).
So i guess im looking for a dis pack now if anyone knows a good place to source
And does anyone have a clue why just one terminal should have done this? It was replaced in may 2005.
Cheers
Si
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Just an update for anyone else having similar problems.
Rocker gasket on drivers side needed replacing, plugs were soaked in oil.
That done I removed the leads and dis pack. Dis pack seems to be the problem, or at least one of them! No6 terminal is badly corroded (all the rest look like new!).
So i guess im looking for a dis pack now if anyone knows a good place to source
And does anyone have a clue why just one terminal should have done this? It was replaced in may 2005.
Cheers
Si
Has it had a squirt of coolant from hbv?
You sure DIS is knackered? Misfire not caused by oil in plug wells?
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Has it had a squirt of coolant from hbv?
You sure DIS is knackered? Misfire not caused by oil in plug wells?
Dis was dry, hbv seems fine plus it would need a miracle to work its way round the rubber plug to the terminal.
Just checked the ht leads, as expected no6 is completely caput :'(
Seen a new dis going on ebay for £79.50 inc p&p. Is that good value?
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DIS packs are expensive. Remember there are 3 different types, so make sure you get the right one...
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DIS packs are expensive. Remember there are 3 different types, so make sure you get the right one...
Yep, they are £75-£95+VAT (depending on type) if you have Vx Trade Club card, so £79 off eBay is not bad - though not a huge bargain either... as TB said, make sure you get the right type.
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I've only read this quick, but am I missing something?
If plug lead 6 is shagged as you mention (as mine was) then surely this is the cause of the missfire, not the DIS?
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The plug lead is knackered where it contacts the dis pack. You should see it. Really bad corrosion on the lead contact and the dis pack terminal is pretty much obliterated.
I'd post a pic if i could work out how to :P
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Have you got a pic showing the numbers on the DIS pack? I've got mine back in and although I thought I was careful they way I've got my leads connected doesn't match up to the way it's numbered in Haynes. Haynes has a drawing of one with the low voltage connector at the back (long edge) and mine is at the side (short edge). I'm hoping I can get a pic of mine where I can see the numbers if I take the scuttle off and then I can make sure the leads are correct before putting the plenum back on.
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Have you got a pic showing the numbers on the DIS pack? I've got mine back in and although I thought I was careful they way I've got my leads connected doesn't match up to the way it's numbered in Haynes. Haynes has a drawing of one with the low voltage connector at the back (long edge) and mine is at the side (short edge). I'm hoping I can get a pic of mine where I can see the numbers if I take the scuttle off and then I can make sure the leads are correct before putting the plenum back on.
See:
http://www.omegaowners.com/forum/YaBB.pl?num=1164668744/3#2
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See:
http://www.omegaowners.com/forum/YaBB.pl?num=1164668744/3#2
Thanks, I have seen that but even when saving the image and blowing it up I can't read the numbering.
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See:
http://www.omegaowners.com/forum/YaBB.pl?num=1164668744/3#2
Thanks, I have seen that but even when saving the image and blowing it up I can't read the numbering.
According to the note I made when i did mine :-
p
[size=20]4 [/size] [size=20]6[/size] [size=20]2[/size] l
u
[size=20]1 [/size] [size=20]3[/size] [size=20]5[/size] g
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According to the note I made when i did mine :-
p
[size=20]4 [/size] [size=20]6[/size] [size=20]2[/size] l
u
[size=20]1 [/size] [size=20]3[/size] [size=20]5[/size] g
Thanks Andy,
Is plug where the low voltage connector is? If that's the case since it's on the left when facing the engine the leads would go to
[size=20]5 3 1
2 6 4 [/size]
That would mean I have 4 and six swapped around so I probably have 3 and 1 swapped as well.
Haynes shows them as
[size=20]2 6 4
5 3 1[/size]
And I think I've gotten totally confused with Haynes and my notes even though I did one bank at a time. It's easy for me these days. I put new lifters and the cams back in last week. After timeing it up I tried turning the engine over and it jammed after about 60 degrees. Took the covers back off to check everything and the cams and shells were correct so I put a rod in each cylinder and moved the engine back and forth but I couldn't see any case where the cams were down while the piston was up. I decided to repeat that on each cylinder again because I must have missed something but then the engine turned over like a dream. Still don't know what was jamming it, cams correct, shells all correct and sprockets correct. I was gentle with it but the engine hadn't been turned over since July so I put it down to a bit of rust around a cylinder wall or a full hydraulic lifter.
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(http://img136.imageshack.us/img136/8303/disv6hv0.jpg) (http://imageshack.us)
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Note: Early Models DIS has different mounting bracket, while Interim and Later Models have same mounting bracket but different multi-plug connector.
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......
Thanks Andy,
Is plug where the low voltage connector is? If that's the case since it's on the left when facing the engine the leads would go to......
Yes. :)
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Thanks again Mark. I think I've got the later model since my plug has three rubber sort of rings around it to keep the water out and the socket on the later version is the one that looks to have room for the seal rings to go in. My car is a January 1997 model though so that has surprised me.
Thanks for the 'Yes' Andy.
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Thanks again Mark. I think I've got the later model since my plug has three rubber sort of rings around it to keep the water out and the socket on the later version is the one that looks to have room for the seal rings to go in. My car is a January 1997 model though so that has surprised me.
Thanks for the 'Yes' Andy.
The DIS packs only ran up to 2000, when they were replaced by individual coil packs, so having a later model unit on a 1997 car should'nt be surprising...
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The DIS packs only ran up to 2000, when they were replaced by individual coil packs, so having a later model unit on a 1997 car should'nt be surprising...
Ah, yes of course. I really must stop using that colander for my memories :)
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I took the scuttle off and managed to get some photos, I got one with 5, 3 and 1 in and another showing 1 and 4 and they are as you say Andy. Luckilly that's how I had them connected anyway. Checking Haynes just confused me - what a surprise :)
[size=20]5 3 1
2 6 4 [/size]
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(http://i23.photobucket.com/albums/b394/Marks_DTM_Calib/DISPack-Verticle-1.jpg)
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That's similar to the picture in the Haynes book of the older DIS pack. It doesn't matter about the banks being swapped around since it fires two at a time but it did confuse me.
View of mine showing 1, 3 and 5.
(http://www.infohitsystems.ltd.uk/Gallery/Car/PC110066.JPG)
Another view showing 1, 3 and 4.
(http://www.infohitsystems.ltd.uk/Gallery/Car/PC110068.JPG)