--MK1 Cupra R 225 Misfire on full boost--

[Poopra R]

(Car is a 2004 Leon Cupra R BAM 225 not mapped has ramair cone filter and miltek cat back)
Hello gents i changed my plugs yesterday all came out smoothy and new plugs in (ngk pfr6q dealer spec same plugs as old one) however now on full boost the car misfires as soon as it hits full boost, ive taken the plugs bvack out and checked the gaps, all ok (0.8mm) and put them back in and same issue, any ideas? the car runs perfectly fine on idle and high RPM only when full boost the misfire happens. code reader said something about EGT sensor but taht could be due to a exhaust leak, any ideas? thank you

 

[welshy46]

If it only started after you changed plugs then I'd say one of the new ones isn't up to snuff. Try putting your old ones back in and see if it still does it. If it doesn't then return them and get a new set.

 

[Poopra R]

If it only started after you changed plugs then I'd say one of the new ones isn't up to snuff. Try putting your old ones back in and see if it still does it. If it doesn't then return them and get a new set.

thank you mate, i done this earlier today to try and find out and same issue, so i put the new ones back in

 

[Rich.T]

Where did you get the plugs from?
Ive heard that you can buy crap lookey likey plugs on ebay.
Not to be used!

Rich

 

[smutts]

Genuine Chinesium!
Probably.

 

[Rich.T]

If they are fakes, you are lucky to have just had a misfire.
The electrodes can fall into the combustion chamber.

 

[welshy46]

That was my thought about the Chinesiun "NGK" plugs. I've seen the iridium ones on ebay for £35 a set, when they're usually £50 plus, but as Poopra tried his old ones with the same result I'm thinking he might have a bad connection to one of the coils after pulling them out. No idea how to test though, I hate electrics.

 

[Rich.T]

Ah, my mistake.
Maybe a coil is starting to break down now its been disturbed

 

[mty12345]

Possibly just coincidence that it happened after changing the plugs, or maybe you disturbed the wiring to the EGT sensor while changing them. Either way, if the ECU is seeing dodgy EGT data, then it will probably be pulling timing/boost under full acceleration. I'd be pretty confident that if you sort the EGT then the 'misfire' will go, as i suspect it's more of a flat spot caused by the bad EGT data rather than an actual misfire.

'

 

[Poopra R]

Possibly just coincidence that it happened after changing the plugs, or maybe you disturbed the wiring to the EGT sensor while changing them. Either way, if the ECU is seeing dodgy EGT data, then it will probably be pulling timing/boost under full acceleration. I'd be pretty confident that if you sort the EGT then the 'misfire' will go, as i suspect it's more of a flat spot caused by the bad EGT data rather than an actual misfire.

'

Thanks, im just sourcing an EGT now, thanks alot for the info.

 

[mty12345]

Thanks, im just sourcing an EGT now, thanks alot for the info.

You're welcome mate. I hope that sorts it for you, let us know how you get on.

 

[Alexis27]

Make sure your EGT is screwed in to the turbo. They can unscrew themselves over time

 

[Poopra R]

thanks. i changed my EGT sensor and still same problem but the code is now gone.

 

[Alexis27]

Did you say you'd put new coil packs in?

 

[mty12345]

Possible that a coil pack is breaking down under full boost or perhaps the fuel pump is struggling to supply enough fuel. If you have VCDS then run some logs under full boost, or if not then use an obd2 reader that can do live data to look at the short term fuel trim when it's happening.

 

[Poopra R]

Possible that a coil pack is breaking down under full boost or perhaps the fuel pump is struggling to supply enough fuel. If you have VCDS then run some logs under full boost, or if not then use an obd2 reader that can do live data to look at the short term fuel trim when it's happening.

thanbks ill have a look, going to try a set of R8 coils from my mate, if that dont work then ill have to get someone to vcds on my car