Hi

My car on returning from a holiday with about 1000 miles of driving, first day back at work decided it had had enough.
It has developed a misfire that is not there when the car is cold but quickly appears as the engine warms up and is very obvious at idle as the car rocks from side to side, however periodically and briefly the misfire disappears. I am unable to tell if the misfire disappears or continues at high revs.

I have checked the sparks by attaching a jump lead between the plug and negative on the battery and all cylinders are all sparking.
I tried removing the HT leads one at a time when the engine was warm to determine which didn't make a difference, removing the front 3 all made the engine more resistant to starting, only the rear made no difference. It does appear that the misfire is consistently on the rear most cylinder even if it is not consistently misfiring.

I am getting a bit of oil in the plug wells but no mayonnaise in the oil or film in the water reservoir, the visual condition of all the spark plugs according to the haynes manual is close to ideal if not ideal (does this imply that at higher revs the misfire disappears or have I not done enough miles with the misfire?). The plugs are however at least 4 years old but I only normally do about 5000 miles a year.

The idle control valve, and the breather needle valve have both been cleaned back in April, I have done about 1500 miles since then.

I am not getting the engine management light showing whilst the engine is running at the moment, I have not tried to read the codes.

I am hoping it is not a fuel injector.

Has anyone got any ideas please?

Do a compression test to rule out anything "mechanical" first mate. :y

Skint wrote on 29. Aug 2011 at 16:12:

Hi My car on returning from a holiday with about 1000 miles of driving, first day back at work decided it had had enough. It has developed a misfire that is not there when the car is cold but quickly appears as the engine warms up and is very obvious at idle as the car rocks from side to side, however periodically and briefly the misfire disappears. I am unable to tell if the misfire disappears or continues at high revs. I have checked the sparks by attaching a jump lead between the plug and negative on the battery and all cylinders are all sparking. I tried removing the HT leads one at a time when the engine was warm to determine which didn't make a difference, removing the front 3 all made the engine more resistant to starting, only the rear made no difference. It does appear that the misfire is consistently on the rear most cylinder even if it is not consistently misfiring. I am getting a bit of oil in the plug wells but no mayonnaise in the oil or film in the water reservoir, the visual condition of all the spark plugs according to the haynes manual is close to ideal if not ideal (does this imply that at higher revs the misfire disappears or have I not done enough miles with the misfire?). The plugs are however at least 4 years old but I only normally do about 5000 miles a year. The idle control valve, and the breather needle valve have both been cleaned back in April, I have done about 1500 miles since then. I am not getting the engine management light showing whilst the engine is running at the moment, I have not tried to read the codes. I am hoping it is not a fuel injector. Has anyone got any ideas please?

Probable cause, lead breaking down

Yep if compreddions ok next check replace Nº 4 (back one) plug lead as that seems to be the dodgy cylinder.

Well new plugs and leads fitted, still missing  :'(

Not been able to check the compression, didn't want to have to buy a tester and not been able to borrow one. I don't understand how compression could be affected that much by engine temperature, would I not be detecting water in my oil or vice-versa?

/sighs
I guess I shall just bite the bullet and replace the coil!

pm sent.

I had similar on the same engine recently and it caused a bit of head scratching too.
I was convinced it was a failed Lambda upsetting the injection ,this was after I'd changed a few components like leads ,plugs cam cover gaskets....., but after a suggestion from here I removed and checked the EGR valve and lo and behold it was sticking open diluting the mixture and thus causing a very uneven idle and a slight miss/hesitation when on load.
I would add that like yours it was OK when cold and only appeared as the car heated up.
I removed it , blanked it off and when refitted problem was gone.
Good luck.

I apologise for interupting, does anyone know if there is a "how to" clean egr? I can't find it and one more thing, any pic if egr valve or at least where is it......sorry?  :-[ I might need to clean it to

danzigfan wrote on 01. Sep 2011 at 11:36:

I apologise for interupting, does anyone know if there is a "how to" clean egr? I can't find it and one more thing, any pic if egr valve or at least where is it......sorry?  :-[ I might need to clean it to

Don't know if there's a how-to, but here's a picture of (the 2.0 version of) it.  Back of the head, next to the DIS.  I seem to remember that it's a T45 torx bit needed to undo the two fixings, but my memory isn't always worth much.
http://images.omegaowners.com/images/guides/2.2_useful_pics/Tempsenders_resize.jpg

Once it's off, you'll see the moving part and what needs cleaning so that the valve will seat well. 

So that's the little ba..... Thanks for quick answer, will try to disasseble it tomorrow as I have day off. Anything to be carefull? Not to make it worse or destroying it? Thank you again :y

danzigfan wrote on 01. Sep 2011 at 12:32:

So that's the little ba..... Thanks for quick answer, will try to disasseble it tomorrow as I have day off. Anything to be carefull? Not to make it worse or destroying it? Thank you again :y

There's one (yellow) electrical connector to take off, and one vacuum pipe to remove (not shown in the image above, but I think it connects just above the dangly one with the black air-filter 'lump' on the end). 

If you do take off the other rubber vac hoses (the ones you can see above) make sure you put them all back correctly or it will run very strangely! (Guess who's tried this by mistake?  ;D)

Probably worth buying a new gasket that goes under the EGR, before removing.  Pennies from Vx.

Oh, so you"ve been there already  ;D Thanks for the advice ::)

Well hopefully I have found someone to borrow a compression tester off of if he remembers it tomorrow.

If the EGR valve is the source would it affect only one cylinder constantly or would it be random?

I note that being attached to the same item the DIS it's going to be a right @r5e to get off.

Skint wrote on 01. Sep 2011 at 17:37:

Well hopefully I have found someone to borrow a compression tester off of if he remembers it tomorrow. If the EGR valve is the source would it affect only one cylinder constantly or would it be random? I note that being attached to the same item the DIS it's going to be a right @r5e to get off.

Can't see why it would affect only pot 4 TBH, but are you 100% sure that it is always pot 4?

Compression test is a good idea, let me know if your lender doesn't remember, I've got one I could pop in the post to you, if you're happy to cover the postage cost.  Remember to prop the throttle open before running your tests.

DIS (and EGR) are slightly awkward to remove, but DIS suddenly looks easier once the HT leads are all off and out the way.  Do make yourself a little sketch of which goes where before you pull them off though.

Another thing to be aware of: although it's tempting to lean on the camcover while you're working 'down the back', it is only plastic, so spread any load out with a cushion or something to minimise the chance of 'squishing'/distorting it with point-loads and potentially disturbing the gasket.  From what you've said yours is already leaking, so this probably doesn't matter so much just now.

Edit: Oh, and do a paperclip test!  Easiest diagnostic aid.  :)

Abiton wrote on 01. Sep 2011 at 18:48:

Skint wrote on 01. Sep 2011 at 17:37: Well hopefully I have found someone to borrow a compression tester off of if he remembers it tomorrow. If the EGR valve is the source would it affect only one cylinder constantly or would it be random? I note that being attached to the same item the DIS it's going to be a right @r5e to get off. Can't see why it would affect only pot 4 TBH, but are you 100% sure that it is always pot 4? Compression test is a good idea, let me know if your lender doesn't remember, I've got one I could pop in the post to you, if you're happy to cover the postage cost.  Remember to prop the throttle open before running your tests. DIS (and EGR) are slightly awkward to remove, but DIS suddenly looks easier once the HT leads are all off and out the way.  Do make yourself a little sketch of which goes where before you pull them off though. Another thing to be aware of: although it's tempting to lean on the camcover while you're working 'down the back', it is only plastic, so spread any load out with a cushion or something to minimise the chance of 'squishing'/distorting it with point-loads and potentially disturbing the gasket.  From what you've said yours is already leaking, so this probably doesn't matter so much just now. Edit: Oh, and do a paperclip test!  Easiest diagnostic aid.  :)

Only plastic!!!! hm well that might have been useful to know several years ago, I cant say then that has not been me that has caused the leak around the cover  :'( I always assume it was a sturdy bit of aluminium that looked nice a 'comfortable' to take my weight.

I will try to read the codes this weekend to see if anything turns up.