Misfire

[mattw 2]

Hi all,

 

Started the Pug for the first time since Christmas last weekend and everyting was fine. However after about 5 minutes it started to miss fire on one of the cylinders. Light revving stopped it but when left to idle it started again.

 

When I checked the plugs, the first hole was full of water! with the others being a bit damp. I do know the reaon for this......fully removable bonnet (removed) and a freaky 15 min blizzard filled the engine up with snow.

 

Now I dried out each plug hole before removing the plugs and cleaning with a wire brush. I dried out the leads and re assembled. However once started, I took it for a quick spin and it started to miss again, so much so that it struggled all the way back home (sounded like it was two cylinders).

 

My question is therefore, what damage has been done and how do I rectify it? Is it just a case of new leads?

 

Cheers,

 

Matt

[welshpug 1,657]

do you recall what's happening at the rev counter when it plays up?

[DrSarty 90 1 Cars]

Remove old plugs, and spin engine over for 10 secs. Dry out plug holes in head (perhaps use a hair dryer). Spin engine over again.

 

Wang some new plugs in and try again.

 

This could be a £12 fix.

 

That's a practical approach and removes one element of doubt. Welshpug's approach is digging down for the problem - which is right - but I reckon this simple swap along with a decent drive will dry everything out and have it funky again.

 

*Places nuts on block*

Edited February 22, 2010 by DrSarty

[MerlinGTI 3]

While you are at it, whip off the dizzy cap, dry out, fine emry cloth the contacts in the cap and the rotor arm. If they are shagged, replace (cheap)

[DamirGTI 342]

Start it up at night (switch all the lights off ) pop up the bonnet and see if you can spot current leaking/arcing around the leads .. it'll be blue spark jumping from either the leads or the coil tower on the surrounding metal , often coped with clicking sound

 

Also , spray the hell out of the leads and all the areas which where damp with WD-40 cos the damp spots make problems even when they're left dried off on the leads/contacts ..

 

Damir

[mattw 2]

do you recall what's happening at the rev counter when it plays up?

 

Not sure as it was dark and my dash lights don't work. The revs were dipping very low as one would expect. What would this tell me and what should I be looking out for?

 

Remove old plugs, and spin engine over for 10 secs. Dry out plug holes in head (perhaps use a hair dryer). Spin engine over again.

 

Wang some new plugs in and try again.

 

This could be a £12 fix.

 

*Places nuts on block*

 

Thought about drying the plug holes with a hair dryer but had visions of blowing a load of crap into the head!

 

So you recon its more likely to be plugs than leads? The leads look pretty old.

[DrSarty 90 1 Cars]

Thought about drying the plug holes with a hair dryer but had visions of blowing a load of crap into the head!

That's the idea behind spinning it over with the plugs out me old China.

 

So you recon its more likely to be plugs than leads? The leads look pretty old.

Well no. But from your explanation, £12 on a set of plugs is hardly breaking the bank.

 

If the leads look old and you'd feel happier replacing them then do so at the same time, although that may set you back between £20-£30.

 

Not possible to diagnose I'm afraid; we can only fault find sometimes by changing things, and a new set of plugs never did anyone any harm. Gives you a chance to see how she's running too.

 

Bear in mind (or is it bare?...yes), bare in mind that swapping the plugs and leads still may not sort it. But...at least you'll know it's not them, and can concentrate on other areas.

 

Merlin's advice was top as well, as it costs nothing. It could be your ign amp or coil breaking down, or even a hairline crack in your dizzy cap you can barely see. Loose rotor arms can cause this too. It's a pain, but you'll find it step by step.

 

So what does the rev counter do then? EDIT> Well Welshpug is seeing if it completely stops reading, as that would indicate the coil at fault.

Edited February 22, 2010 by DrSarty

[welshpug 1,657]

Exactly my line of thinking Rich, if the rev counter drops then its a spark generation issue, be it a faulty component or power supply to a component.

 

If it stays pretty level it'll be a spark transfer issue, i.e leads dizzy cap/rotor or the plugs.

 

just a simple yes or no that'll give you a direction to go when tracing/rectifying the fault.

 

 

 

 

 

Maybe its time to fix that dash lighting issue

 

Should be no more than an unplugged dimmer switch, blown sidelight fuse, or an earth problem.

 

Fairly important to have them working IMO as you do need to know what the engine vital stats are up to

[mattw 2]

That's the idea behind spinning it over with the plugs out me old China.

 

Ahhh, that makes sense!!

 

 

Well no. But from your explanation, £12 on a set of plugs is hardly breaking the bank.

 

If the leads look old and you'd feel happier replacing them then do so at the same time, although that may set you back between £20-£30.

 

Not possible to diagnose I'm afraid; we can only fault find sometimes by changing things, and a new set of plugs never did anyone any harm. Gives you a chance to see how she's running too.

 

Bear in mind (or is it bare?...yes), bare in mind that swapping the plugs and leads still may not sort it. But...at least you'll know it's not them, and can concentrate on other areas.

 

Merlin's advice was top as well, as it costs nothing. It could be your ign amp or coil breaking down, or even a hairline crack in your dizzy cap you can barely see. Loose rotor arms can cause this too. It's a pain, but you'll find it step by step.

 

So what does the rev counter do then? EDIT> Well Welshpug is seeing if it completely stops reading, as that would indicate the coil at fault.

 

Well looks like first stage is a new set of plugs and leads! - Any reccomendations of make/suppliers?

 

 

Exactly my line of thinking Rich, if the rev counter drops then its a spark generation issue, be it a faulty component or power supply to a component.

 

If it stays pretty level it'll be a spark transfer issue, i.e leads dizzy cap/rotor or the plugs.

 

just a simple yes or no that'll give you a direction to go when tracing/rectifying the fault.

 

 

Maybe its time to fix that dash lighting issue

 

Should be no more than an unplugged dimmer switch, blown sidelight fuse, or an earth problem.

 

Fairly important to have them working IMO as you do need to know what the engine vital stats are up to

 

Will check out the rev counter when I get some day light.

 

I've only just noticed the dash lights not working as its a track only car...only ever work on it/drive up and down my private road in the daylight! I will get onto it anyway as its best to get these things sorted!

 

Thanks for the advice.....I'll get the parts ordered and get back to you guys (hopefully yo tell you its Better!)

Edited February 22, 2010 by mattw

[mattw 2]

Double Post

Edited February 22, 2010 by mattw

[MerlinGTI 3]

NGK plugs everytime. BCP7ES for 1.9 GTI.

 

OE spec leads from GSF, although im quite fond of the ones from performanceleads.co.uk for like £5 more.