Misfiring cylinder one

[Avante]

I own a 6y2 2005 skoda fabia 1.4 16v AUB 100HP, and had problems with it going into limp mode only when sat idled for about 3-5 minutes. After checking the service history I had notice individual spark plugs and ignition coils had been changed, so I've replaced all 4 spark plugs for NGK BKUR 6ET-10 as recommended by Haynes, and replaced all 4 coils as recommended too, this gave it a much steadier idle but the problem still persisted. I then went on to trying Redex petrol injector cleaner which seemed to work, I left my car idling for 30 minutes and it idled smoothly with no misfiring, when I'd turned the engine off then back on later the engine management light had disappeared and I thought my problem was solved until this morning when it went back into limp mode after 5 minutes or so of idling. I did only use 75mm of injector cleaner as I only had half a tank of fuel (I tend to try keep it at half instead of full). Maybe I should use the other half and top my fuel up? Just looking for suggestions as to what I could try next. Code reader gave error code cylinder 1 misfiring, when I swapped coil 1 for 2 the problem jumped across to cylinder 2, so I'd thought new coil packs would have solved my problem.

[Breezy_Pete]

Are you using normal or super unleaded?

 

How many miles has the engine done?

[Avante]

Sorry its a BBZ engine - I'm a fairly new driver and fairly new to all this mechanical looking after your car malarky. I'm running super unleaded (Texaco vpower or tescos super) and its done 110k miles.

[KenONeill]

A misfire on cylinder N normally indicates an high tension electrics fault on something that only feeds that cylinder. In this case, that would tend to point to either the signal lead for that coilpack, the coilpack itself or the spark plug.

 

Bad spark plugs are not unknown, so if you still have the old plugs, fit one of them and see if that clears the misfire. If it does, good.

 

If not, swap the offending coilpack with one of the others, and see if the misfire follows the coilpack or stays put.

 

If the misfire follows the coilpack, then replace the coilpack. If it stays on the same cylinder, suspect the low tension signal lead and do a continuity check with a multimeter.

 

Oh and stop using cr@ppy supermarket fuel!!

[Avante]

Haha thanks I'll stick to vpower now, I haven't yet brought a code reader but intend on getting one soon!

All 4 spark plugs and 4 coil packs were replaced yesterday, I'll hook it up again to see of the code follows with the new coil packs when swapped.

As for the injector cleaner, any residues I should be looking for on the injector heads to see of they need cleaning without taking it apart?

[Breezy_Pete]

It's not clear from your first post whether you've scanned it since this morning's limp mode episode? I think not?  If so it will be interesting to see which cylinder is being reported for misfires this time.

[Avante]

I haven't as stated I've only limited access to a code reader until I purchase one (should be this weekend). I'll get it hooked up as soon as I can. I can't see a new problem arising from replacing spark plugs and coil packs though, only the same problem persisting as the problem isn't solved maybe due to leads or something.

I'm merely searching for possible causes of cylinder 1 misfiring besides coil packs, spark plugs, and leads.

Appreciate the advise, I do hope it is the leads, I don't see that being too expensive of a repair.

[Breezy_Pete]

Could try swapping cyl 1 injector to somewhere else to see if the misfire follows that. Other thing that may be worth doing is a compression test to see if that adds any relevant info. 

[Avante]

Is swapping injectors as simple as swapping spark plugs and coils? Trying to keep costs down by doing labour myself. Already spent about £150 trying to solve this problem.

[Avante]

Pictures of the two codes that came up initially, the other is to do with my air con which I don't use, so I'm not particularly in a rush to get it fixed.

Edited 25 June, 2015 by Avante

[Avante]

Ordered a vag code reader, will arrive Monday. I'll run checks and keep updating. Anyone in my area who needs access to a code reader I'll happily lend a helping hand (notts)

[Avante]

Code reader has arrived, code has been cleared and problem appears to have vanished (touch wood) although I have code 17961 now, which I believe may be something to do with the fact my exhaust box Is corroded to the point it's shedding lol.

[Breezy_Pete]

Dunno about exhaust, (which end of the system is disintegrating?), here's the diagnostic suggestion for that code:

 

 

Seems like air leaks, MAP sensor, Purge valve, EGR are some of the things to check out.

[Avante]

Dunno about exhaust, (which end of the system is disintegrating?), here's the diagnostic suggestion for that code:

Seems like air leaks, MAP sensor, Purge valve, EGR are some of the things to check out.

Wow! You know what I've done something really silly. I've a strong feeling I know what it is. I was locating my oil filter yesterday to see if the socket I had would fit, and forgot to replace the engine cover properly! Doh! I'll replace it and recheck for codes.

[Breezy_Pete]

I'm not convinced that would cause it, but hope so!

[rum4mo]

I'd second the "injector swop" if misfiring returns, I have a crazy feeling that some time ago this cylinder one misfiring was thought to be related to a common(?) wiring failure on the top of the engine - could be wrong though, maybe use the search function.  If you use the search function using 17961 might expand your thoughts. One thing that I've found that these engines do, is to clog up the EGR valve pipe on the TB or its I/F plate, which causes problems. I replaced the MAP sensor on wife's 2003MY BBY engine for a second hand earlier version when I had 17961 codes logged, maybe just clean the MAP using brake cleaner and not carb cleaner - also do not spray directly into the end of the MAP sensor.

[Avante]

I'd second the "injector swop" if misfiring returns, I have a crazy feeling that some time ago this cylinder one misfiring was thought to be related to a common(?) wiring failure on the top of the engine - could be wrong though, maybe use the search function. If you use the search function using 17961 might expand your thoughts. One thing that I've found that these engines do, is to clog up the EGR valve pipe on the TB or its I/F plate, which causes problems. I replaced the MAP sensor on wife's 2003MY BBY engine for a second hand earlier version when I had 17961 codes logged, maybe just clean the MAP using brake cleaner and not carb cleaner - also do not spray directly into the end of the MAP sensor.

Sorry I don't really know what most of those things are, of course I'll google it though - replaced engine cover and breather pipe and scanned for codes and nothing. I'll try again tomorrow. Also car went into limp mode with no engine management light?

[Avante]

I've been reading about through some previous similar topics and believe that due to my car only ever going into limp mode when idling, it'll be a block(ed/ing) EGR valve/pipe. Any information on how I can clean this, I read some people suggest to remove the pipe both ends to clean it properly?

[Avante]

Cylinder 1 misfire appeared again today. Also when taking off in low RPM the engine sounds like its rattling. Maybe the thermal valve in my engine cover is dodgy or the EGR is blocked? It just doesn't like idling lol.

[Avante]

Considering taking injectors out to clean, gonna flush the engine and put some new oil and a filter - is there a way I can find out if it's the flap in the engine cover?

[Breezy_Pete]

I think you'll soon see whether the EGR pipe is blocked at the inlet manifold end, by lifting the throttle body off to get  visual access.  I doubt there's any need to take the whole pipe off, it's probably easy enough to clean the bit that gets blocked with the pipe in situ.  Use a vacuum cleaner to suck debris out of there as you loosen it with a bent bit of wire or suchlike.

 

The image below shows the airbox flap arrangement in the cold-air-only position (I think!, it was a while ago now), with a working thermostat (albeit one off a Volvo, but that's irrelevant, I hope). Note how much steel pin is sticking out of the brass housing of the 'stat.

As these stat's lose wax, that pin sticks out less and less at a given temperature (this photo was at room temp, 21C or so, I think) until they don't do anything at all, and the flap stays in the no-cold-air position. Try warming the brass body with a hair-dryer etc. and see whether your pin comes out to play or not.

 

 

Edited 25 February, 2019 by Wino
Picture fix

[Avante]

I think you'll soon see whether the EGR pipe is blocked at the inlet manifold end, by lifting the throttle body off to get visual access. I doubt there's any need to take the whole pipe off, it's probably easy enough to clean the bit that gets blocked with the pipe in situ. Use a vacuum cleaner to suck debris out of there as you loosen it with a bent bit of wire or suchlike.

The image below shows the airbox flap arrangement in the cold-air-only position (I think!, it was a while ago now), with a working thermostat (albeit one off a Volvo, but that's irrelevant, I hope). Note how much steel pin is sticking out of the brass housing of the 'stat.

As these stat's lose wax, that pin sticks out less and less at a given temperature (this photo was at room temp, 21C or so, I think) until they don't do anything at all, and the flap stays in the no-cold-air position. Try warming the brass body with a hair-dryer etc. and see whether your pin comes out to play or not.

Last I checked my pin was inside the housing and didn't protrude at all.

[Avante]

I've just done a "readiness test" and it's told me that catalyst, evap sys, 02sensor, heated 02 and EGR system have failed - heate cat and sec. Air sys have passed.

[Breezy_Pete]

Even when warmed up a bit? On my original, the only 'part number' info of any sort was a stamping on the end of the brass housing "15-23".I suspect those are the temperatures at which the pin is fully in and fully out, respectively. So it shouldn't take much if any warming for it to protrude of it's not waxless.

[Avante]

There is no protrusion so should I assume it needs replacing?