Octavia VRS misfire

[Dazl1212]

Hi guys,

 

My Octavia 1.8t VRS seems to be misfiring a little, I've done a fault code scan and it hasnt picked anything up. 

 

I had leaking rocker gasket replaced a few months back and I'm wondering if this may have caused it while it was leaking?

Also have a slight hole between the exhaust and tail pipe. 

[Ray Luxury-Yacht]

Describe the misfire.

 

If it's a very sudden jerky misfire it's almost 100% a coil pack failing.

 

If it comes and goes, surges....then....could be anything

 

But a good place to start is to check all the breather hoses and dipstick tube, common fault on these, any small split in any of them can cause a misfire. Yes, it's a massive ball-ache but you can't go chasing a problem without these fundamentals checked first.

 

Then could be one of the sensors, MAF and CTS are favourites. Can check the MAF by unplugging it and going for a drive, don't worry it's fine and the check engine lights will extinguish once you reconnect it. If it drives better with an unplugged MAF without a misfire then could be that.

 

Last one is to clean the throttle body, there's a guide on here on how to, DON'T touch it before reading the guide or you can buy yourself even more problems.

 

Good luck

[Dazl1212]

Describe the misfire.

 

If it's a very sudden jerky misfire it's almost 100% a coil pack failing.

 

If it comes and goes, surges....then....could be anything

 

But a good place to start is to check all the breather hoses and dipstick tube, common fault on these, any small split in any of them can cause a misfire. Yes, it's a massive ball-ache but you can't go chasing a problem without these fundamentals checked first.

 

Then could be one of the sensors, MAF and CTS are favourites. Can check the MAF by unplugging it and going for a drive, don't worry it's fine and the check engine lights will extinguish once you reconnect it. If it drives better with an unplugged MAF without a misfire then could be that.

 

Last one is to clean the throttle body, there's a guide on here on how to, DON'T touch it before reading the guide or you can buy yourself even more problems.

 

Good luck

Cheers mate, much appreciated 

[Ray Luxury-Yacht]

Pleasure dude. These are just the basics, a starting point for you.

 

You didn't describe the misfire...can you be more specific?

[Dazl1212]

Pleasure dude. These are just the basics, a starting point for you.

 

You didn't describe the misfire...can you be more specific?

Yeah sure, basically its most noticeable at idle, the revs drop off and go up a few hundred RPM. Its worse when the car is cold. It runs on LPG and its not nearly as noticeable when its running on LPG.

 

When I'm driving its not really noticeable, the car doesn't seem as quick and I've had the Turbo stop boosting if I push it too hard but it comes back on if the car is left for an hour or so, although I havent noticed it do this on Petrol. So I'm wondering if that's to do with the LPG map its running on as I had the car back in with them a bit ago, as it was running too lean which caused the ECU light to come on. The guy who did the conversion noticed this and said it could be the spark plugs. I cant get them off to check as theyre on too bloody tight 

 

Hope this helps :-)

Edited 18 July, 2016 by Dazl1212

[Leeboy]

Misfire on idle sounds like you should be checking all the pipe work associated with the emissions recirculation gubbins.

[Dazl1212]

Misfire on idle sounds like you should be checking all the pipe work associated with the emissions recirculation gubbins.

If its not too simple, I will struggle.   I'll have a look at that as best I can though.

 

Thanks 

[Dazl1212]

Hi guys, sorry for the late replies, Ive just started a new job so Ive been a little snowed under.

 

Anyway after it seemingly getting worse where it where when it was idling it would drop and jump up a few thousand revs I decided to have a look at it today.

 

I checked every hose I could see and couldnt find any obvious leaks or holes and I checked the wires leading to the ignition packs, nothing obvious there, except one wire seems to have lost its protective outer sheath.

 

So I lifted one of the ignition packs off and tried to remove a spark plug, when I lifted my spark plug tool out, its too short so its very hard to get the leverage on to remove them, it was covered in oil. I dont think when my rocker gasket cover was fixed they bothered to clean the spark plugs. I cleaned all the spark plugs, well the top half. As I only managed to remove one and cleaned the inside of the ignition packs with cotton buds. 

 

It seems to be a lot better now, still very slightly erratic but nothing like it was before.

 

Think my next job will be to change the spark plugs. They were NKG plugs but stamped with VW. Makes me wonder if they have ever been changed.

[rsdanne]

hey there man i just  found out what made my car have jumping idling it could even die when stopping for a redlight all the sudden and after that go okey for a while but the jumpy idling always came back mostly it was on idle  but it could stutter on low rpm aswell under 2000rpm it often stuttered

 

i have spent loads of money before i  figured it out so this is worth looking up  check your air temperature sensor it is located on the intake manifold just next to the throttlebody mine had a thin layer of burned oil on the metal strings i just took a scissor and scraped carefully so that it got clean and had the metal color all over again and after that

 

no jumpy idling no stutters it feels like a diffrent car

 

now i can start the car from idling almost

 

before if i started on low rpm it felt like it almost died 

[Dazl1212]

hey there man i just  found out what made my car have jumping idling it could even die when stopping for a redlight all the sudden and after that go okey for a while but the jumpy idling always came back mostly it was on idle  but it could stutter on low rpm aswell under 2000rpm it often stuttered

 

i have spent loads of money before i  figured it out so this is worth looking up  check your air temperature sensor it is located on the intake manifold just next to the throttlebody mine had a thin layer of burned oil on the metal strings i just took a scissor and scraped carefully so that it got clean and had the metal color all over again and after that

 

no jumpy idling no stutters it feels like a diffrent car

 

now i can start the car from idling almost

 

before if i started on low rpm it felt like it almost died 

Thanks man, I will check this out ASAP.

 

Think I need to change the sparks plugs and give the Ignition packs a really good clean as well.

[rsdanne]

no problem man =)

[SuperbTWM]

Have a look at the wiring loom for the coil packs. The insulation is bad for breaking down and once you disturb the loom by doing something like removing and replacing the rocker cover it can cause misfires.

 

I would of thought the car would have logged codes for misfiring but you never know

[Ray Luxury-Yacht]

Hello again matey!

 

Ahhh......I've just caught up on this thread, and seen that your car is running LPG....right, that changes things a bit now as well (possibly....)

 

6 or 7 years ago, I had a car fitted with a modern, multipoint LPG system. I drove it home.....then after a few days, is started to misfire quite badly, but only when it was running LPG, it was fine on petrol.

 

I called the company who fitted it, and they asked me what spark plugs I had fitted, and apologies, they normally check, but as I had pressed them for a quick turnaround, they didn't check before I took it away...

 

My car had some Champion plugs fitted.

 

The company then told me that for some reason, 99% of spark plugs other than NGK plugs could often cause misfiring problems when running on LPG. They told me to fit some NGK Plugs, and that when I did, they were sure that I would never have another problem.

 

I fitted NGK plugs and......I never had another problem!

 

A strange anomoly......but one worth trying on yours.

 

 

A quick Google round finds one website of many recommending this:

 

http://www.go-lpg.co.uk/Hints.html

 

 

Quote: "NB! Go LPG only recommend the use of NGK spark plugs for all LPG operation, they are consistently the best plugs for gas applications. You can get expert advice on plug slection by ringing the NGK Technical Hotline on 01442 281000"

[Dazl1212]

Hi Guys,

 

I have had a look at the cables that connect to the ignition packs and one of them, the brown one for the first one on the left has lost its insulation. 

Could this be a contributing factor? Will I need to replace the whole rail with the wires on? 

 

I cant seem to find the air temp sensor near the manifold, I did disconnect the MAF and this made things ten times worse.

 

I have only managed to get one of the spark plugs out. It looks like an NGK iridium plug, its VW stamped looks clean but does seem to have a slightly pink tinge.

 

The misfire doesn't seem as bad on LPG oddly.

[rsdanne]

here is a pic of where the airtemp sensor is located on the intake manifold

 

[Dazl1212]

Hi guys,

 

Anothjer potentially more serious issue.

 

One of my tyres was flat today.. when i looked under my car the entire inside half was bald 

Similar to this.

 

Took it to get changed and asked the guy at the garage what it could be and he said back wheels are out like the beam is twisted.

 

He said it could be the tracking at the front and something to do with the bushes at the back, said they could try doing the tracking at the front and aligning the back through the brushes. Anyone heard of this? They said I wouldn't be charged if it didn't work, but how would i know if it has?

 

The other tyres is similar but only about an inch is worn on the inside.

[rsdanne]

hey man sorry to hear about more probs  =/ hope you'l get it sorted out 

 

have you looked at the air temp sensor yet 

 

best regards

[Dazl1212]

hey man sorry to hear about more probs  =/ hope you'l get it sorted out 

 

have you looked at the air temp sensor yet 

 

best regards

Thanks mate,

 

I havent as of yet. I plan to look when the weathers a bit better this week, or should that be if? 

 

I love the car when it works, which hasnt been much if I'm honest. I'd hate to get rid of it as its a perfect car for me with it being on LPG and quick.

Do you know if I can just replace a damaged wire on the coil pack loom?

[rsdanne]

aah okeej haha rough weahter for you in uk ?

 

its realy windy here in sweden today  but has'nt rained yet 

 

about the  damaged wire i dont realy know  it might work 

 

 dont you have junk yards to buy cheap parts from in the uk might be a good thing to replace all of it if you could get a good price on it

[Dazl1212]

aah okeej haha rough weahter for you in uk ?

 

its realy windy here in sweden today  but has'nt rained yet 

 

about the  damaged wire i dont realy know  it might work 

 

 dont you have junk yards to buy cheap parts from in the uk might be a good thing to replace all of it if you could get a good price on it

Yeah mate, typical schizo UK weather. Sunny one minute torrential rain the next 

 

Will probably be weekend if as I'll need to replace the "O ring" 

 

I'll have see how cheap I can pick a loom up as it looks like a right pain to fit so will need someone too look at it.

[Dazl1212]

A thought just occured to me..... 

 

When I bought the car it had an atmospheric dump valve fitted. 

 

After reading it could harm performance etc I took it off and put the old plastic recirc valve on. I've read they can fail and cause issues. Could this be the cause?

[rsdanne]

try to suck air through the hose on the top of the dumpvalve if you feel air entering your mouth without lifting the piston then the dumpvalve is leaking

 

my bet is still on the airtemp sensor just one screw so a real easy diy fix, if it has burned oil  on it just scrape it off and see if it improves the idle as mine did

 

i bought a new one yesterday just to be sure because the o-ring on mine was damaged 

Edited 10 August, 2016 by rsdanne

[Dazl1212]

Cheers mate, I had another shredded tyre and RAC had to rescue me, caused by the issue I made another thread on.

 

Dropped it off at the garage and got a lift home. I will definitely get this checked out when I get the car back tomorrow. 

[YellowCar]

Use carb cleaner on the intake temp sensor rather than risk damaging the wire. You can soak it for a while.

[Dazl1212]

Use carb cleaner on the intake temp sensor rather than risk damaging the wire. You can soak it for a while.

Pretty sure i have a tub of that still lying about.