Plug electrodes burning out ?

[wellsy]

Hi all my 98 v70 t5 has been running fine for years now but the other day I noticed when I accelerated the car juddered really bad and seemed to misfire , I checked the plugs a day or so later and found that the plugs from cylinder 1-2 the electrodes were burnt off ,I replaced the plugs and car seemed back to normal but a day or so later the juddering was back and the same plugs were gone again , I've noticed looking down the plug hole of these 1st 2 cylinders the piston top looks wet not sure if it's fuel . The car doesn't use water or I've not noticed any smoking the motor seems quite no rattles I'm hoping it's not the end of my dear old t5 any one have any ideas please of what could be causing this , I've noticed a broken rubber elbow which goes to the inlet manifold from the hard black pipe that runs under the fuel rail cover .
any help very great fully received .thanks wellsy :-)

[Orca2]

What make of plugs are you using?

[wellsy]

They are ngk bkr7evx ,I've used them in there for the past 8 years or so with no probs , the car does have a Rica 310 map but has run fine for years with no issues ,I'm just hoping this is nothing too terminal

[M-R-P]

Might be running a bit lean on 1 and 2?

[jamesy12345]

as MRP said might be running lean..maybe injectors needs a clean? could that elbow be letting air in although that wouldn't explain only 2 pots being affected

[LeeT5]

Codes?

Air leak?

[wellsy]

Thanks guys , not checked for codes yet will do later no lights have come on though .
Was thinking maybe injectors playing up ,could they be overfilling on those cylinders causing plugs to burn out as these 2 look wet down plug holes ,fixing the elbow later and going to do compression test to hopefully rule out anything sinister .

[wellsy]

Just done compression test cylinders 1-2 were 150-160 psi cylinders 3-5 were 165-175 so not a huge difference it's done just under 210,000 tried another set of old plugs gave it a spin still missing under hard acceleration but will Rev right out cleanly stood still ,not sure to change dizzy cap and rotor arm both have some arcing on terminals .could a injector problem cause missing under load ?
thanks guys for replys ,love my old car just hope I can get it sorted :-)

[Orca2]

Burned up electrodes is usually lean rather than rich, you could do a flow back test on the injectors to check they are all working properly .

[LeeT5]

Thanks guys , not checked for codes yet will do later no lights have come on though .
Was thinking maybe injectors playing up ,could they be overfilling on those cylinders causing plugs to burn out as these 2 look wet down plug holes ,fixing the elbow later and going to do compression test to hopefully rule out anything sinister .

If the injectors were leaking and over fuelling the cylinders then you'd have loads of dark grey smoke from the exhaust and the plugs would be black. Over Fueling does not burn out plugs but the opposite, like Orca2 says.


Just done compression test cylinders 1-2 were 150-160 psi cylinders 3-5 were 165-175 so not a huge difference it's done just under 210,000 tried another set of old plugs gave it a spin still missing under hard acceleration but will Rev right out cleanly stood still ,not sure to change dizzy cap and rotor arm both have some arcing on terminals .could a injector problem cause missing under load ?
thanks guys for replys ,love my old car just hope I can get it sorted :-)

Looks like you don't have weak compression, those results are pretty good.

Before you go replacing parts, willy nilly, it would be nice to actually diagnose and work out the problem!

To test the Rotor arm is simple:

1. Remove HT lead from coil to dizzy cap - at the dizzy cap end.
2. Remove the dizzy cap without removing the HT leads and set aside.
3. Get a third party to sit in drivers seat and poised to turn ignition over.
4. Hold HT lead with non conductive pliers about 0.5" away from middle part of rotor arm (the part that makes contact with middle of the dizzy cap). ##Do not use your bare hands to do this!!
5. Get third party to crank engine....

~If you see a spark, no matter how small, jump from the HT to the rotor arm then your rotor arm is knackered and needs replacing as it's shorting to earth.
~If you don't see any spark, then your rotor arm is good and you just need to make sure the ends is clean and shiny. Give it a scratch up with some emery cloth!

You can't really test the cap, but if there is evidence of tracking or the 5 contact point looks corroded or electrically dirty, then you need to replace it.

You can check each HT lead with an ohm meter but you'll need to know the resistance of each lead to see if one of them is too high.

Check you have battery voltage at the coil.

if you decide to just replace the HT leads, cap and rotor arm then can I advise you only buy OE especially for the HT leads. In my experience, pattern part HT leads never fit properly and are nearly always too long and made of cheap subgrade insulation material. OE parts won't be cheap but at least you'll be guaranteed the good quality and perfect fit. :wink:

## Getting a jolt of 40,000v is enough to ruin your day or at best make you wanna sit down for 20 minutes feeling sick, but on a serious note, if you have a weak ticker or any form of undiagnosed heart condition a jolt of the cars HT could literally kill you!

It is also possible that your ignition coil may be breaking down. They get hot and when under load, it may be shorting out internally. Fairly common too.

I know this is a lot to digest, but I hope it helps you fix your problem because to me, it sounds ignition related. If you have a weak spark, then your engine will misfire, especially under WOT or under load.
Did you take any pictures of your spark plugs? You'll be surprised just how much information they can tell you mate. the clues are there, you just need to understand how to interpret them.

[wellsy]

Thanks guys ,have just had a thought just lately I have had a funny noise coming from the motor sounded like something whining,I was wondering if what I could hear was air leaking from the inlet manifold gasket ,the noise is from that end of the motor and earlier I tried the old long screwdriver to ear test on all the rotating stuff and heard nothing ,if it is leaking that would explain just the 1st 2 cylinders having trouble and I'm thinking that when on boost the problem would be worse with the extra pressure .

[LeeT5]

Thanks guys ,have just had a thought just lately I have had a funny noise coming from the motor sounded like something whining,I was wondering if what I could hear was air leaking from the inlet manifold gasket ,the noise is from that end of the motor and earlier I tried the old long screwdriver to ear test on all the rotating stuff and heard nothing ,if it is leaking that would explain just the 1st 2 cylinders having trouble and I'm thinking that when on boost the problem would be worse with the extra pressure .

Maybe??

A smoke leak test would show that up straight away!

[wellsy]

Hi guys quick update got a new inlet gasket which I was going to change today but while removing the fuel rail and injectors I noticed that on injector 1-2 the little plastic shim that sits at the base of injector was all cracked and broke gone very brittle also the rubber o rings looked a bit worn ,I'm hoping this is what is causing the leanness on these 2 cylinders ,Imgoing to order the new seal kit Monday so fingers crossed the old t5 will live on for a few miles yet :-)
thanks guys for all replies and help :-)

[MoleT-5R]

Hi guys quick update got a new inlet gasket which I was going to change today but while removing the fuel rail and injectors I noticed that on injector 1-2 the little plastic shim that sits at the base of injector was all cracked and broke gone very brittle also the rubber o rings looked a bit worn ,I'm hoping this is what is causing the leanness on these 2 cylinders ,Imgoing to order the new seal kit Monday so fingers crossed the old t5 will live on for a few miles yet :-)
thanks guys for all replies and help :-)

are you still going to change the inlet manifold gasket just to rule it out....??

[wellsy]

Hi yeah going to change it ,it's all in bits just have to get the injector seals ordered next week :-)

[MoleT-5R]

Hi yeah going to change it ,it's all in bits just have to get the injector seals ordered next week :-)

worth doing the pcv whilst the manifold is off and you can get to it easily, if it hasn't had it done recently

[wellsy]

thanks ,was thinking of giving pcv a going over as well , it was done a few years back but like you say worth doing while its easy to get at .
ordered a seal kit today so going to get new gasket on and give it all a good clean ready go back together and fingers crossed the problem will be gone :-)

[wellsy]

Hi guys ,quick update , I replaced all the injector seals and inlet gasket tested injectors all were seemed fine the pcv system was replaced not long back and was very clean so put it all back together and went for a spin , runs a lot better than before but still has a slight misfire at the top end pulls like a train but just a bit of missing :-(
im not sure if it's the denso plugs which are old ones I had on the shelf that it never really run well with I've ordered some ngk' sand new dizzy cap and rotor arm , also found a few perished hoses mainly the ones that go to the turbo and waste gate actuator so are replacing these as well and then fingers crossed again the old boy will be back on top form :-)
thanks guys wellsy :-)

[LeeT5]

Hi guys ,quick update , I replaced all the injector seals and inlet gasket tested injectors all were seemed fine the pcv system was replaced not long back and was very clean so put it all back together and went for a spin , runs a lot better than before but still has a slight misfire at the top end pulls like a train but just a bit of missing :-(
im not sure if it's the denso plugs which are old ones I had on the shelf that it never really run well with I've ordered some ngk' sand new dizzy cap and rotor arm , also found a few perished hoses mainly the ones that go to the turbo and waste gate actuator so are replacing these as well and then fingers crossed again the old boy will be back on top form :-)
thanks guys wellsy :-)

Use genuine plugs and I'd be very careful fitting pattern parts especially where dizzy caps, HT leads and rotor arms are concerned. From experience, they tend to not fit well, leads are way too long and rotor arms are usually made of substandard plastic that won't last 5 minutes!
I'd just fit OE, then you can't go wrong!

Top end misfire sounds spark plug related as at higher boost and more load, the plugs have gotta work 10 times harder to produce a good spark. If they can't then you'll get a misfire. Spark plugs are so very often overlooked, yet people forget they are an integral part of the ignition system and will make a big difference.

[kmb]

I just bought Bosch HT leads, rotor and distributor cap for my 850 T5, they turned up yesterday - it was less than £100 delivered...

If I'd gone with high quality non OEM parts it could have been done for £65, after some thought I went Bosch as they're such critical parts.

# 1 234 332 390 Bosch Rotor
# 1 235 522 408 Bosch Cap
# 0 986 357 232 Bosch HT Leads

They'll not be fitted for a few weeks but all feel high quality!

Maybe I've wasted £35, but hey.... it's OEM :lol:

[Redbrick]

I buy Bosch parts from http://www.buycarparts.co.uk/ try and pay with PayPal as their credit card process is weird I guess due to being victims of online fraud.

Leads from PartsForVolvo, Bougicord, they are even stamped up as Volvo on he leads but don't come in the blue box.

[kmb]

I buy Bosch parts from http://www.buycarparts.co.uk/ try and pay with PayPal as their credit card process is weird I guess due to being victims of online fraud.

Leads from PartsForVolvo, Bougicord, they are even stamped up as Volvo on he leads but don't come in the blue box.

Same guys I used, although I contacted them and went via their French website as I'm in France, only marginally cheaper though.

I noticed they all came from Warsaw in Poland when checking the manufacturer locations on the Bosch packaging...

[wellsy]

Yeah have got Bosch rotor arm and dizzy cap plugs are ngk bkr7evx that I've used in the car for the last 10 years with no probs so stuck with them , I have a set of magnecor kv85 leads to go on as well , hopefully will cure the little miss fire I'm having at top end :-)

[wellsy]

Just finished replacing plugs dizzy cap rotor arm replaced a load of perished vac pipes oil and filter and the old Volvo seems to live on , back as it was pulls like a train again no misfires :-)
hopefully it's cured ,thanks for all the help in above posts guys
cherrs wellsy :-)