Petrol Diagnostics

Post a Response

Skoda Fabia 1.4 2002 - Misfire codes on cylinders 2 & 3 - Fixed #

Posted by Andy Broomhead on February 4, 2015, 9:42 pm

Year of Manufacture *: 2002
Engine Size and Code *: 1.4
( Optional ) Scanner Used: VCDS

Misfire codes on 2&3 when engine gets warm.
Injectors 2&3 loose trigger pulse but this looks like Cat protection because one of the coil triggers also is lost when engine starts to warm up.
Load test wiring from coil back to ECU all good.
Compression check on cold engine all cylinders reach 200 after 8 secs cranking. Cant do live compression.
Garage had changed the plugs and coil pack (non genuine) before I saw car, or I might have suspected coil pack drawing to much from the ECU although looking at the coil trigger pattern this is nit a usual driver signal but a very small squarewave trigger to switch the electronics in the coil pack so is not doing any "work" as such.
So its chicken and egg I feel. Is the ecu faulty and loosing the coil trigger or is the coil pack overloading the ecu causing it to shut down the injectors?
Or could there be another factor causing CAT protection?
Cup of tea and sleep on it I think. any thoughts please

Re: Skoda Fabia

Posted by Ian Whitmore on February 5, 2015, 8:10 am, in reply to "Skoda Fabia"
Edited by board administrator February 6, 2015, 2:55 pm

Hi
Engine code would be usefull,
If this is a 16V engine we have seen quite a few lower mileage ones have problems with valve guides causing misfires.

Re: Skoda Fabia

Posted by Andy Mason <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2936' width='330' height='300' border=0 style='border:none;'> on February 5, 2015, 8:54 am, in reply to "Re: Skoda Fabia"
Andy Mason

We have also had a problem with valves on this type of engine, sticking and burning out. (cant be more specific without engine code as stated)
Andy

Re: Skoda Fabia

Posted by James Eardley <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3143' width='330' height='300' border=0 style='border:none;'> on February 5, 2015, 10:15 pm, in reply to "Re: Skoda Fabia"

Hi Andy

Using VCDS I would think you would have MVB for misfire counts.
You mentioned that you did compression test from cold. Monitor the misfire counts and conduct the compression test when the misfires are most frequent or straight after the ECU shuts down the injectors. Better still, quickly pop scope on and do a relative compression and see if you can verify the suspect cylinders are/are not sealing correctly.

Regards
James

Fixed #

Posted by Andy Broomhead on February 6, 2015, 8:16 pm, in reply to "Skoda Fabia 1.4 2002 - Misfire codes on cylinders 2 & 3 #"
Edited by board administrator February 10, 2015, 1:00 pm

Posted this morning but dont know what happened?
Anyway engine only done 30K but is old 8v AWQ i think.
The best scope I have is on the Modis so I dont think I could do relative compressions, and did look for misfire counts (no label file) went up to 160 but couldnt see any
But I did scope the current for both coil triggers and did notice the trace didnt cut dead but did a bit of stop starting first. The outcome was a high resistance building in the multiplug. New fishtail on connection pin 3 and all is sorted.
Thanks

Re: Skoda Fabia 1.4 2002 - Misfire codes on cylinders 2 & 3 #

Posted by Anthony Pickering <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3715' width='330' height='300' border=0 style='border:none;'> on February 8, 2015, 12:30 pm, in reply to "Re: Skoda Fabia 1.4 2002 - Misfire codes on cylinders 2 & 3 #"
Anthony Pickering

I know this is fixed but if you only have a modis without a current clamp then a method of relative comp test is to put the positive lead close to the starter motor body and negative lead on batt negative post, the volt drop on a scope will show peaks similar to a current waveform.

Two volt scale should be good, if not a lot of detail AC coupling will magnify the peaks.

Used this trick with my verdict. Ok you cant assess the current draw against the battery Ah but for a single cylinder misfire it will show a cylinder in trouble or not in trouble.

Re: Skoda Fabia 1.4 2002 - Misfire codes on cylinders 2 & 3 #

Posted by Lee Mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on February 8, 2015, 1:04 pm, in reply to "Re: Skoda Fabia 1.4 2002 - Misfire codes on cylinders 2 & 3 #"
Lee Mackintosh

Ant,

why can't you use a current clamp with your verdict?

Re: Skoda Fabia 1.4 2002 - Misfire codes on cylinders 2 & 3 #

Posted by Anthony Pickering <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3715' width='330' height='300' border=0 style='border:none;'> on February 8, 2015, 2:04 pm, in reply to "Re: Skoda Fabia 1.4 2002 - Misfire codes on cylinders 2 & 3 #"
Anthony Pickering

I do have a current clamp which has the banana jacks now but when I first had the verdict I only had the Pico clamps and I don't have the bnc-4mm adaptor.

Just used the above method when I was in the field with just the verdict and looking at a misfire.

« Back to index

[ Petrol Diagnostics ]