850: 850 T-5R misfire

[duke1]

Originally Posted by PSJVTHEBEST

Thanks mate. Dizzy cap and rotor arm are Bosch, I am afraid. Gave myself a few shocks with the HTs mucking around and I did notice a strange arcing going on at the dizzy cap when one plug was dangling with the engine running! Maybe a problem with the leads? I haven't changed them yet (and maybe should do now) because I couldn't find any decent ones on line.

lucas do a decent set of ht leads and half the price of oe stock,been on my car 4 years now and a good few thousand miles and still working fine and no corrosion or rot or stray sparks!easy found on ebay,good luck

[PSJVTHEBEST]

Thanks. I'll have a hunt for them.

[PSJVTHEBEST]

Couldn't find the Lucas ones so opted for a set from a company called formula power ignition leads but a bit pricey at £79.95. Also bought some genuine Volvo plugs from Caffyns for £61.32. If anyone needs to know the Volvo part number for the plug set is 8692071 and the HT / ignition lead set 9135700. Once fitted I will report back. Hoping it's not a valve issue!

[ASt85]

Originally Posted by PSJVTHEBEST

Couldn't find the Lucas ones so opted for a set from a company called formula power ignition leads but a bit pricey at £79.95. Also bought some genuine Volvo plugs from Caffyns for £61.32. If anyone needs to know the Volvo part number for the plug set is 8692071 and the HT / ignition lead set 9135700. Once fitted I will report back. Hoping it's not a valve issue!

You would save a significant of money by ordering from FRF Swansea and quoting "C" to get the forum discounts

https://www.volvoforums.org.uk/showthread.php?t=57125

NB try ringing them early morning as they do get very busy during the day. I rarely use any other supplier as they often come out a lot cheaper for OEM parts than even generic parts suppliers.

[PSJVTHEBEST]

Thanks - I'll bear that in mind.
On a different topic, now my problem has changed from 'won't start' to 'misfire', has anyone got any idea how to edit the thread's title?
Cheers.

[ASt85]

Originally Posted by PSJVTHEBEST

Thanks - I'll bear that in mind.
On a different topic, now my problem has changed from 'won't start' to 'misfire', has anyone got any idea how to edit the thread's title?
Cheers.

Probably best way would bt to contact the moderators using the "contact us" button on the lower right hand side of the page in question.

[PSJVTHEBEST]

Thanks matey

[ASt85]

Originally Posted by PSJVTHEBEST

Thanks matey

No problem, a thought occurs....if it runs very rough on start up after a long period of not being used it could be a lack of compression issue - this can be resolved by removing the plugs and putting 10 to 20mls of engine oil or upper cylinder lubricant down each bore, then winding the motor over through 5 revolutions or more by hand to distribute the added oil then re-installing the plugs and attempting to start - the lack of compression is caused by the oil having completely drained down due to lack of engine use or petrol washing down the oil on the cold bore side walls and piston rings which reduces the compression to either cause a no-start or rough start.

The added oil re-seals the bore and lifts the compression ratio back to normal UCL or engine oil burning off on a restart will not damage the cat!! Used to happen with 850 if I turned the engine off after less than three minutes running - often referred to a mower syndrome.ie moving the car a very short distance before mowing the grass!

[PSJVTHEBEST]

Originally Posted by ASt85

No problem, a thought occurs....if it runs very rough on start up after a long period of not being used it could be a lack of compression issue - this can be resolved by removing the plugs and putting 10 to 20mls of engine oil or upper cylinder lubricant down each bore, then winding the motor over through 5 revolutions or more by hand to distribute the added oil then re-installing the plugs and attempting to start - the lack of compression is caused by the oil having completely drained down due to lack of engine use or petrol washing down the oil on the cold bore side walls and piston rings which reduces the compression to either cause a no-start or rough start.

The added oil re-seals the bore and lifts the compression ratio back to normal UCL or engine oil burning off on a restart will not damage the cat!! Used to happen with 850 if I turned the engine off after less than three minutes running - often referred to a mower syndrome.ie moving the car a very short distance before mowing the grass!

Thanks. I would say that was a good pointer although it starts fine and runs rough straight away and continues that way even after a few minutes. I'm guessing that the oil should have circulated into the bores by then and so eliminated the misfire? That said, I'll try anything while waiting for the new plugs and leads to arrive! When you say crank by hand, do you mean on the key but with all plugs out, coil disconnected and injector relay removed?

[ASt85]

Originally Posted by PSJVTHEBEST

Thanks. I would say that was a good pointer although it starts fine and runs rough straight away and continues that way even after a few minutes. I'm guessing that the oil should have circulated into the bores by then and so eliminated the misfire? That said, I'll try anything while waiting for the new plugs and leads to arrive! When you say crank by hand, do you mean on the key but with all plugs out, coil disconnected and injector relay removed?

If the engine starts and rough runs straightaway the oil is washed down by unburnt petrol so the engine will continue to run roughly until it stalls. On the odd occasion mine would only crank over and over again without starting at all until I put oil down the bores.

I turned the engine over several times using a ratchet drive on the lower pully before replacing the plugs and then starting the engine - it will smoke a lot but should run evenly.