Engine 850: B5252S/2.4/10v: Missfire/plug leads

[LPGjonderby]

Originally Posted by Mike_Brace

With lpg you have to have the right plugs - do not use platinum or split fire plugs. Use either a copper core or iridium plug. Any mis-fire will be more pronounced on lpg as lpg requires a higher voltage to produce the spark as the gas is dry and does not conduct as well as wet petrol.

Mike

I was running single electrode NGK's, these have now been swapped for twin electrode NGK's. Both are copper core. Alas the iridium plugs were £10 each ! So gave them a miss. The missfire is very much more pronounced on LPG, its just finding what is causing it. At 80 it does shake the poor old thing, the alternative is to thrash it everywhere and drive through it !!

Cheers

Jon

[LPGjonderby]

A couple of ideas

Am going to assume that an inlet valve is sticking, so will order a can of Wyn's combustion chamber cleaner.

Has anyone ever tried it ? Although I don't think a valve is sticking !

Have visited a different garage today with a big Bosch computer, could they get it to communicate with my engine ? Could they hell. Although I at least now know that it is my O/S rear wheel sensor that there computer thinks is faulty and chucking the ABS lights on.

They wanted £35 for a download, told them to get stuffed and keep their super duper Bosch !

So still missfiring like a good un !

Jon

[Mike_Brace]

Go back to a single electrode plugs. The twin electrode do not work well on lpg.
On my 240s which are a little more primitive I have had problems with various ignition parts at different times and now have come to the conclusion that the genuine Volvo parts are better value for money in the long term. Not to mention the aggro factor.

Mike

[LPGjonderby]

Hi Mike

Thats what I thought, which is why it was on bobby basic plugs.

As this was the last thing to change I thought it was worth a go, so bought the ones which NGK recommended. These being the twin elctrode ones for a petrol.
However it runs just the same for the time being, i.e missing like a monster on petrol and gas. So not the plugs either.
Will give the wyns fluid a go when it arrives in the post, although am 99% sure its not a sticking valve stem.

After that its getting hold of a man I have been put in touch with that has some mobile tunning gear including a scope. Problem is its now been too 4 different garages including the man I normaly use ! Nobody has a clue as to why its missfiring and I cant go on swapping bits at will. The downloads are a complete waste of time as are the fault codes they sometimes show.

Todays being a good example, this super Bosch kit couldn't even communicate with the car. So they plugged in a hand held code reader that said no codes listed. This is whilst the ABS & Lambda light are on !

I have rang and visited a couple of so called Volvo specialist in the area, half expecting them to know what they are talking about. Had no ideas, but were happy to charge for a download !!!!

At some point, very soon, I will give in and get used to the missfire.

Cheers

Rant over

Jon

[LPGjonderby]

Have thrown a can of forte' gas cleaner in today, it must be almost neat as there is only a a couple of gallons of fuel in him.

Does anyone have experience of this stuff ? Any good ?

The can of wyns combustion chamber cleaner should be here on Tuesday.

Does anyone have experience of this stuff ? Any good ?

Fingers crossed its a sticky valve and the car stops it missfire !

Then again

[Mike_Brace]

I know these additives will work on cars that have failed their emissions at MOT.
You really need someone with a good old fashioned Crypton tuner that will be able to see exactly what is happening where and what voltages are. The OBD is limited as to usefulness in these circumstances. Sadly most garages have thrown out their old ryptons for these hand held diagnostics which don't tell all. I still have a gut feeling that you will find that something like the leads are not quite up to scratch. I have had cases of new items being of poor quality or faulty.
The fact that you say the problem occurs randomly on all cylinders does really narrow it down to coil or leads. OK your coil was passed at ok but was it checked out for producing the required voltage when the engine is under load. My suspicion is that it is not producing sufficent voltage in these conditions or the leads are breaking down under high voltage.

The only other thought - I haven't seen any mention of whether you have checked for air leaks as this will cause the problems you describe as well.

Mike

[LPGjonderby]

Originally Posted by Mike_Brace

I know these additives will work on cars that have failed their emissions at MOT.
You really need someone with a good old fashioned Crypton tuner that will be able to see exactly what is happening where and what voltages are. The OBD is limited as to usefulness in these circumstances. Sadly most garages have thrown out their old ryptons for these hand held diagnostics which don't tell all. I still have a gut feeling that you will find that something like the leads are not quite up to scratch. I have had cases of new items being of poor quality or faulty.
The fact that you say the problem occurs randomly on all cylinders does really narrow it down to coil or leads. OK your coil was passed at ok but was it checked out for producing the required voltage when the engine is under load. My suspicion is that it is not producing sufficent voltage in these conditions or the leads are breaking down under high voltage.

The only other thought - I haven't seen any mention of whether you have checked for air leaks as this will cause the problems you describe as well.

Mike

Hi Mike, thanks for the message & ideas

The first set of replacement leads are 7mm cores, the second that are now on are 10mm ones designed for T5 monsters. The car behaves the same on both. The coil that is now on is the third one I have tried. Again it behaves the same on all three. All three were tested, at different levels of voltage and were producing a good strength and constant output. Am loathed to buy another, although it would be a brand new one. The only parts that were not tested were the coil modules.

The cap and rotor are now Volvo/Bosch parts...just the same missfire as when new OEM parts fitted.

Having ran him today and yesterday on petrol with the gas treatment in the fuel, the car is still missfiring on petrol and on gas, having pulled the plugs, you can see the residue it has left behind, so I assume it has done something.

The next thing is to try the Wyns combustion cleaner. This is fed directly into the chambers via a vacum hose. So will try it through the air filter one when it arrives in the post. This is assuming there is a sticking valve or valves and it works ! Although this would not account for the sporadic missfire shown on all of the leads with the timing light!

You have suggested checking for air leaks ? Do you have any specific ideas ?

I have pulled off the two vacum hoses I can find, both are sucking air when checked with my tongue ? There is the one to the air filter I am going to suck the wyns cleaner through and another leading to the inlet manifold from the tree on top of the throttle housing. I then have another which goes to the bottle of valve saver. I think thats it ? There are a couple of inlets on the tree/branch with caps on.

Do you know what the one on the air box does that is above the vacum hose leading to the base of the box ? I assume this opens the hot/cold air flap ?
This I can get no vacum from so have assumed it needs to be connected ?

Are there more air pipes I need to check ?

Today it has been missfiring badly, again it does it worst between 2,500 & 3100 revs.. Although if you are giving hard acceleration you hardly notice. It is most noticable when crusing around 75-80mph.

My last try next month having been paid again ! Is a man with a mobile set of kit that has an "Oseloscope" (speeling) and some old fashioned crypton gear as you have noted. Am not going to use any more so called Volvo specialists or Bosch type people. To be fair, they have less idea than me !!! In fact they have all been next to useless !!! Apart from wanting £35 for a download!!! On a car that runs a cap/rotor etc it just daft.

Thanks for listening if you have got this far.

Jon

[jeremycolley]

"Although this would not account for the sporadic missfire shown on all of the leads with the timing light!"

Perhaps the problem is with the distributor itself. Volvo trouble shooting document suggests checking distributor pickup coil air gap or replacing the pick up coil for 'above idle' missfire. Might just be something got in there when you first replaced the cap and rotor arm?

Jeremy

[LPGjonderby]

Hi Jeremy

Also many thanks for your reply...being honest you have lost me there !!

Sorry for being a little ignorant but what is the "distributor pickup coil air gap" and what is this Coil ?

Thanks

Jon

[jeremycolley]

Originally Posted by LPGjonderby

Hi Jeremy

Also many thanks for your reply...being honest you have lost me there !!

Sorry for being a little ignorant but what is the "distributor pickup coil air gap" and what is this Coil ?

Thanks

Jon

Jon - I have to be honest and say I don't know either! I was reading through a Volvo trouble shooting pdf and this was suggested. However, it is a generic guide and I don't think it applies to the 850/V70 series as everything is under the control of the ECU. On electronic ignition systems the points are replaced by an optical switch (hence the air gap). Sorry to mislead you - perhaps someone else can expand on what function the distributor performs on these engines - ie are there any servicable parts inside it?