Spark plugs and radio interference - Murena 1.6

[Roly]

Having replaced my spark plugs recently, I am getting more interference on my stereo.

The old ones were BP6ES and I replaced them with RN9YCC - sorry for the mixed brands but I don't know much about plugs.

I'm told the Champion equivalent of BP6ES is N9YC so the RN9YCCs just have the resistor ( I think?) and a double copper core.  

So I would have expected less interference but clearly I'm wrong so please educate me.

Thanks,
Roly

[Anders Dinsen]

Radio interference is difficult to track and does not always behave as one would expect. I suggest you switch back to the original spark plugs to rule out any other causes to the problem.

[Roly]

It's strange - the interference, which is clearly ignition based (clicking and engine speed related) seems to come and go depending on radio station and engine speed.  

I can't change the plugs back as they are probably in a landfill somewhere.  What is the standard fit?  Or is there an upgrade?

I think I will be getting a new stereo anyway so I will wait and see how that one sounds before changing the plugs again...

Thanks,
Roly

[Anders Dinsen]

Well, it's not an exact science, so I suggest you make some experiments before writing the final conclusion

Please let us know what you learn!!

[roy4matra]

Having replaced my spark plugs recently, I am getting more interference on my stereo.

The old ones were BP6ES and I replaced them with RN9YCC - sorry for the mixed brands but I don't know much about plugs.

I'm told the Champion equivalent of BP6ES is N9YC so the RN9YCCs just have the resistor ( I think?) and a double copper core.  

So I would have expected less interference but clearly I'm wrong so please educate me.

You are correct Roly, the Champion RN9YCC are roughly the equivalent of NGK BP6ES - it's just that they have resistors in which would be the actual equivalent of NGK BPR6ES.  These resistive plugs were originally supposed to improve interference, but I've often found they are worse or unreliable, and consequently stick to the non-resistive type.   One reason they can make things worse is that in an old system the added resistance makes more arcing across gaps like the rotor arm to distibutor cap, creating more interference.  Is the earth wire to your engine cover still fitted?  This should make sure the metal engine cover can provide an interference shield.

You don't often get a lot of interference on old systems anyway these days.  However, you do have to be careful with the latest highly electronic systems and on many Renault you can get all sorts of problems just by using non-standard plugs!

I would go back to the BP6ES if I were you.  I've used them for years in all my 2.2 Murena and they have always been brilliant.

Roy