Need help diagnosing engine running rough

[360beast]

Yes that will be the week and the year, the cylinder head is stamped the same as are tyres. My 940 registered 1997 had something like 36 96 on the head meaning 36th week of 1996 so I know my car was built in 96.

They have quite a bit of chaffing on the insulation where they've been cable tied in place. I would recommend getting new ht lead clips too.

https://classic-volvo.com/catalog/pr...eel-1306510_b/

[Laird Scooby]

Originally Posted by griston64

They look in remarkable condition for 25 year old leads !

Mine looked remarkable at 30 years old when i changed them because #3 plug lead had broken just inside the sprak plug boot and was causing an intermittent misfire - fell into two pieces when removed despite having been intact physically up until that point.

Before you ask, no i didn't break it on removal, it fell apart after removal.

As for date codes, they can take various forms, year or week # first, sometimes they use month numbers depending on their internal system and other times the exact calendar date is given.
For the most part it's year - week though and just for fun, some manufacturers start the year in April so for "97-17" would put it in August some time.

However that tends to be a UK thing and most others use the normal week numbers, making those leads as Salvador says, sometime in April/May of 1997.
Just had a look to see if i have a pic of my original leads that i changed in ~July 2018, just short of the cars 30th birthday. Only the new ones though.

[SalvadorP]

Originally Posted by Laird Scooby

Mine looked remarkable at 30 years old when i changed them because #3 plug lead had broken just inside the sprak plug boot and was causing an intermittent misfire - fell into two pieces when removed despite having been intact physically up until that point.

Before you ask, no i didn't break it on removal, it fell apart after removal.

As for date codes, they can take various forms, year or week # first, sometimes they use month numbers depending on their internal system and other times the exact calendar date is given.
For the most part it's year - week though and just for fun, some manufacturers start the year in April so for "97-17" would put it in August some time.

However that tends to be a UK thing and most others use the normal week numbers, making those leads as Salvador says, sometime in April/May of 1997.
Just had a look to see if i have a pic of my original leads that i changed in ~July 2018, just short of the cars 30th birthday. Only the new ones though.

They don't make rubber like they used to.
"Before you ask, no i didn't break it on removal, it fell apart after removal."
It just knew it could finally rest in peace.

If i dint know they were 25yo i would bet my life they weren't the original leads. Will be ordering some asap.

[Laird Scooby]

Originally Posted by SalvadorP

They don't make rubber like they used to.
"Before you ask, no i didn't break it on removal, it fell apart after removal."
It just knew it could finally rest in peace.

If i dint know they were 25yo i would bet my life they weren't the original leads. Will be ordering some asap.

What didn't help with mine is someone had obviously been swapping plug leads around (previous owner at a guess, seems he was forever tinkering and misdiagnosed several things!) and had stretched #3 plug lead. It's already yhe shortest on the engine as it's nearest the dizzy :



Given there's also a lot of heat around the front of the engine as well, the combination of stretching and constant heating/cooling would have aged the rubber prematurely.

[Ian21401]

Re Luke’s comment in post #131 and your 2nd image showing the two leads fastened together. They appear to be next to plug 3 which seems to indicate that one of the leads is routed to plug 2.
I try to avoid having two leads fastened together from experience in the very distant past when I had a lead shorting to another lead which was routed alongside it. Those “chafing” marks referred to by Luke could actually be sites where the lead has been shorting to something else. I’ve seen similar marks on leads which have been shorting out.

[Laird Scooby]

Originally Posted by Ian21401

Re Luke’s comment in post #131 and your 2nd image showing the two leads fastened together. They appear to be next to plug 3 which seems to indicate that one of the leads is routed to plug 2.
I try to avoid having two leads fastened together from experience in the very distant past when I had a lead shorting to another lead which was routed alongside it. Those “chafing” marks referred to by Luke could actually be sites where the lead has been shorting to something else. I’ve seen similar marks on leads which have been shorting out.

Excellent points Ian and the two leads that are closest to the metal loop they are cable tied to (and which is then bolted to the engine making it earth) are for #2 & #1 cylinders so could very well be arcing out.

It takes a higher voltage to fire the weaker mixture on idle so the stray voltage may find it's an easier path to earth to arc through a rupture in the insulation straight to that bracket! Wouldn't be the first time i've known this happen!

[SalvadorP]

But i did soak them pretty well yesterday and i dint notice anything.
Anyway. It's time to change them based on age alone. If it's not that, I'll keep chasing.

The cables were tied together when i bought the car, so i never bothered to untie them.

Btw guys, is it normal to be able to see spark inside through the hole in the picture? Is that arcing or just normal spark when the rotor passes the contact closer to the hole?

[Ian21401]

Sorry SalvadorP, I don’t know the answer to that one.

[Laird Scooby]

Originally Posted by SalvadorP

But i did soak them pretty well yesterday and i dint notice anything.
Anyway. It's time to change them based on age alone. If it's not that, I'll keep chasing.

The cables were tied together when i bought the car, so i never bothered to untie them.

Btw guys, is it normal to be able to see spark inside through the hole in the picture? Is that arcing or just normal spark when the rotor passes the contact closer to the hole?

Yes, it is normal. The rotor arm can't make physical contact with the contact segments so the spark jumps or arcs from the rotor to the segment nearest.

As for the HT leads, they play up in damp weather and if you soaked them, all you'd notice is prolonged rough running. It won't magically make the lost sparks visible.

When you get the new HT leads, like Luke said make sure you use the proper plastic clips/separators to mount them, don't cable tie them to a piece of metal!

[Ian21401]

Quote:
When you get the new HT leads, like Luke said make sure you use the proper plastic clips/separators to mount them, don't cable tie them to a piece of metal!

The clip is part no. VO28436510. I obtained mine from my main dealer.
They come complete with the plastic clip secured to the metal fishplate.