Help, Mis-firing after oil and spark plug change

[Scottyleon]

Hey folks,

Carried out a spark plug and an oil change today.

Did the spark plug change first. When warming up the engine to prep for oil change engine seemed fine. Went out tonight and when idling every 10sec or so there is a judder which is slight. Also sometimes when driving about there is a big judder until 2000rpm. Engine light flashed but went off and stayed off.

Any ideas?

Cheers

 

[lee_woollett]

mine has recently done this, it turned out that one of the spark plugs wasn't tight enough and the pressure was pushing the coil pack of the plug, causing it to misfire. Check this first.

 

[james walker]

Did you torque the plugs up to the correct setting?

 

[Scottyleon]

I only tightened by hand and guess it wasnt tight enough for vibration. My torque wrench is wrong size so when i checked today i tightened more as it was loosened from fitting. And the juddering is slight now and not so violent so day off tommorow to get an adapter to use torque wrench so i can torque to correct setting.

Cheers for your help, just silly error at end of day and glad is not major.

 

[Pabs]

you could have a knackered coil pack. Mine went 3 hours after changing my plugs. Did exactly as you describe.

If you've got access to VAG-COM this would confirm it.

 

[shauncupra]

My money is on a coil pack failing aswell, mines been having a habbit of that lately lol..
(Remaps are fun though)
also as for the plugs not being tight enough, they really should only be just nipped up to seal, and not seriously tight.

 

[lee_woollett]

my coil packs have been fine since i had the loose spark plug.

 

[shauncupra]

ah im glad you sorted it mate, just a thought..

 

[james walker]

My money is on a coil pack failing aswell, mines been having a habbit of that lately lol..
(Remaps are fun though)
also as for the plugs not being tight enough, they really should only be just nipped up to seal, and not seriously tight.

not quite mate, they should always be torqued correctly. not just nipped up.

the correct torque figure is 30nm

 

[flak monkey]

I would put my money on the coil pack not making a decent contact with the plug due to some dirt on the contacts over anything else.

If the plugs have a conical seat (which AFAIK they do) then they should seal up ok just nipped up. 30Nm is a pretty light feel even on a ratchet.

 

[james walker]

30nm sourced from etka and haynes

 

[Scottyleon]

well, torqued to correct settings. went for a drive today all was well until engine light flashed and has stayed on, car lost power, think went into limp mode. switched off and back on, cars power came back. investigated under the bonnet and found one of the coil packs has a bump on its surface.

will VAG-COM it tommoroow when get a shot from a mate, but has anyone had a coil pack with a bump on it? i guess the coil pack is shot?

Would the car behave this badly just for one pack failing?

Cheers

 

[flak monkey]

Yep, a dodgy coil pack is enough to upset it in a big way

 

[Scottyleon]

With time on my hands and an impatience for having to wait for the VAG-COM, I tried the method of having the engine running and taking out the coil packs one by one, and which pack i pull out that does not affect idle will give me my duff coil pack.

The coil pack that i thought was duff is actually ok, i then managed to come across the coil pack, phew there was only one

I then changed over the duff one for the good one just to confirm it is the coil pack that is duff and not wiring etc. That was successful, so looks like i have found i have one dodgy coil pack that needs replacing , but at least it wasnt major.

 

[flak monkey]

Glad you found the cause of your problem

 

[Scottyleon]

changed coil pack today and was much better, but there is still a slight hesitation sometimes.

I let the engine idle and pulled the coil packs one by one again. All made a difference to engine idle so that was ok. next test was the pop pop pop sound when you take the coils off. 3 popped but 1 did not.

Does this mean the 1 that did not pop is semi-working but on its way out and needs replaced?

Cheers

 

[Markyboyt]

I'd be changing the one with the bulge in, also check for cracks etc on the coil packs. Ive seen coil packs (not on a Seat) that have cracked slightly and bulged out, Bremi crap.

 

[dainott2105]

Just my 10 pence but i would buy genuine coilpacks only (and make sure they have R at the end of the part number) as i thought i was a smart arse and got an aftermarket set and out of 4 new packs 2 were knackered!! I spent hours trying to figure it out as i had fitted new spark plugs aswell. Just not worth the hassle IMO. Glad its sorted though fella.

 

[Scottyleon]

Would a semi-working coilpack cause problems?

the coil pack does not pop pop pop when lifted off but does make a diffrence to engine idle.
the rest of the coil packs pop pop pop when lifted and make a diffrence to engine idle. so, just a query about the pop pop pop would cause misfire?

cheers

 

[Scottyleon]

All sorted now, replaced 2nd coilpack that was semi-working and hey presto running smooth just like a boucht ene!!!