Distributer Cleaning, Have I Gone Too Far!?

[LPTJoe]

Originally Posted by monkeh

Another point to consider is to check wiring for crank position sensor. I remember mine produced a slight miss, before intermittent no start.

Monkeh, did you replace the crank sensor as a whole or just check/repair the wiring?

[960kg]

We never ever cleaned inside the cap the contacts or the rotor arm as this is carbon which is more conductive so the spark will jump an even more smaller gap?

The leads can be prone to cause misfires but all these Volvo products are very good quality it is usually a poor owner cutting down on prices but still wants the best from his motor.

For my monies worth it is the plugs causing the misfire. Volvo plugs are what Volvo`s run on best so why not fit them?.....especially but not only turbo`s.

Yes, other plug`s work they have to but get to around 5 or 8,000mls and they won`t give the best like Volvo plugs do.

This fact has gone around the houses for years on here Volvo plugs used to be produced by NGK but now Bosch make them to Volvo spec.

You cannot buy a NGK or Bosch plug under a different number as it is copyright so they have to have Volvo written on them.






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[Laird Scooby]

Originally Posted by 960kg

We never ever cleaned inside the cap the contacts or the rotor arm as this is carbon which is more conductive so the spark will jump an even more smaller gap?

The leads can be prone to cause misfires but all these Volvo products are very good quality it is usually a poor owner cutting down on prices but still wants the best from his motor.

For my monies worth it is the plugs causing the misfire. Volvo plugs are what Volvo`s run on best so why not fit them?.....especially but not only turbo`s.

Yes, other plug`s work they have to but get to around 5 or 8,000mls and they won`t give the best like Volvo plugs do.

This fact has gone around the houses for years on here Volvo plugs used to be produced by NGK but now Bosch make them to Volvo spec.

You cannot buy a NGK or Bosch plug under a different number as it is copyright so they have to have Volvo written on them.
.

They make resistors out of carbon because it is not very conductive.

He's already mentioned the HT leads have corroded end connectors - good chance it's the leads - after the plugs won't fire at all, regardless of brand if the leads have gone high resistance due to corroded terminals!

Originally Bosch made spark plugs for Volvo, fairly sure it's NGK now, would be interested to see some sort of paper trail (even a virtual one online) to see when/how the changes happened. I'm confident that both Bosch and NGK make high quality plugs that are direct equivalents of the "VOLVO" branded plugs but ideally plugs should be cleaned at 6k miles and renewed at 12k miles.
That said, i'm guilty of forgetting to do either on my 827 Sterling, the plugs have been in for 22k miles now so could do with renewing! When i got my current 760, i checked the (NGK) plugs in it, only to find they were in fact about 10 years old but still the car ran. It was only a slightly reluctant cold start when winter came that prompted me to check them!

[Rumbo]

I’ve always found that cleaning the throttle body and intake manifold.Changing the plugs and leads makes a very nice difference with the Volvo and any car...

[AllHailKingVolvo]

Thanks all new plugs and leads ordered, plus a new rotor arm and coil just in case. Handy to have in the spares box even if I don’t need them this time. Got some heatsink paste on the way too!

Throttle body is clean as a whistle as of last weekend which made the car a little smoother and keener to rev, which is the same effect that the job had on all my previous Volvos. I’m really enjoying bringing this great car back to its best. Still plenty to do, but by the end of summer it will be good to go all autumn and winter with little more required than keeping it fed with fuel...





...in theory!

[AllHailKingVolvo]

Changed the plugs (NGK), HT leads (Bosch) and coil (NGK)...

The car has LOADS more midrange power and is much smoother to drive. The old plugs were a good colour but were clearly elderly and the gaps were all over the place, all too big and in the case of #4 close to 2mm!

The slightly shuddery idle remains, though. Any other suggestions as to what i should be chasing? In tank pump perhaps? Is there a fuel filter in line that I should be changing to ensure good pressure at the injectors?

[Laird Scooby]

What should you be chasing Phil? Roadrunner (Neep - neep!) all the way to Weymouth down the A31 (or whichever road it is, long time since i was there) with the "pedal to the metal" all the way.

Before you do that though, ass some injector cleaner to the fuel tank. In other words, injector cleaner and an Italian decoke.

Oops, just noticed my little typo above! Normally i would go back and change it but i'll leave it for comedy value!

There is a fuel filter, it's under the passenger seat accessed by jacking the car up and undoing three 13mm hex-headed bolts and the whole plate supporting the main fuel pump and filter drops down. Unless it's holding back under maximum load - going uphill, accelerating or high speed driving, i wouldn't think the fuel filter would improve matters. As a matter of prevetive maintenance, if you don't know when it was done or it was more than 24k miles, change it. Also check all your rubber fuel lines for perishing, all the way from the tank to the front. If they perish not only can fuel leak out, but air can leak in.
Under idle conditions, the pressure at the injectors is the lowest it will be for practical terms. A Wide Open Throttle (WOT) gives maximum pressure at the injectors. If air is being sucked in through a perished hose then that will be most obvious at idle. Also check your engine and gearbox mounts as surprisingly, these can make a difference to idle quality.

[AllHailKingVolvo]

Originally Posted by Laird Scooby

What should you be chasing Phil? Roadrunner (Neep - neep!) all the way to Weymouth down the A31 (or whichever road it is, long time since i was there) with the "pedal to the metal" all the way.

Before you do that though, ass some injector cleaner to the fuel tank. In other words, injector cleaner and an Italian decoke.

Oops, just noticed my little typo above! Normally i would go back and change it but i'll leave it for comedy value!

There is a fuel filter, it's under the passenger seat accessed by jacking the car up and undoing three 13mm hex-headed bolts and the whole plate supporting the main fuel pump and filter drops down. Unless it's holding back under maximum load - going uphill, accelerating or high speed driving, i wouldn't think the fuel filter would improve matters. As a matter of prevetive maintenance, if you don't know when it was done or it was more than 24k miles, change it. Also check all your rubber fuel lines for perishing, all the way from the tank to the front. If they perish not only can fuel leak out, but air can leak in.
Under idle conditions, the pressure at the injectors is the lowest it will be for practical terms. A Wide Open Throttle (WOT) gives maximum pressure at the injectors. If air is being sucked in through a perished hose then that will be most obvious at idle. Also check your engine and gearbox mounts as surprisingly, these can make a difference to idle quality.

Dave, again absolutely mega advice-thankyou! I have no idea when the filter was changed, having had a nose underneath it looks positively Jurassic, so I’ve ordered a replacement Bosch filter just to make sure it’s fresh and to eliminate it as a possible cause. The car motors along nicely on flat terrain but does struggle on hills a bit. The midrange of the engine is respectable (and very much improved by the new properly gapped plugs and leads) but it does seem to run out of puff a bit at the top end. I know the NA motors have relatively narrow powerband though, so I’m not too concerned. Hopefully the filter change might spice it up a bit though!

[Laird Scooby]

Filter change, injector cleaner and a long fast run (Italian decoke) should have it singing the right tunes at all times Phil.

If not then there's something, somewhere that's been missed or perhaps you've just got one that will only ever idle slightly "off-beat" - had a few cars like that, they could be set up absolutely spot-on for everything and they'd still tick over like a bag of spanners. Just one of those things.

Fingers crossed though, yours just needs that last little bit of TLC and job's a good'un!

[AllHailKingVolvo]

Yeah i’ve had a couple of cars that just wouldn’t idle smoothly whatever I did to them, I know what you mean...I really think that the 740 wants to idle smoothly, it just has a shudder every so often. Nothing major, but I’m optimistic that the filter change and some decent injector cleaner with a good thrash will help. I’ve had good results with Forte in the past so have ordered a bottle of that which should arrive at the same time as the filter with a bit of luck!