Mixing Spark Plugs ?

[Tham]

Can spark plugs be mixed ?

Number 2 and 3 plugs on my KE70's 4K engine
tend to foul (oily carbon soot) pretty fast, and I
guess the valve seals and/or piston rings are worn.
The engine is consuming quite a bit of oil.

I use standard NGK BP5ES. I was wondering if
replacing the above two with a brighter spark type,
BP5ES-11 to help burn off the soot, might be alright,
or may cause misfiring.

I had initially used BP5ES-11 on all four, and was
wondering why my engine was running much hotter
than usual, until a parts dealer told me that this had
a more powerful spark and was meant more for
newer fuel injection engines.

[oldcorollas]

no, they are both the same heat range, and 5 is pretty warm.

if they are fouling, check the mixtures first, as well as the compression.

standard plugs have 0.8mm gap.
the -11 plugs have 1.1mm gap.
there is no real benefit in a standard 4K to having larger gapped plugs, apart from making it more likely to miss...

[TRD-12A]

Unless ofcourse you run an electronic controlled dizzy, i done this with a mates ke20 which has a 4k in it, i chucked away the points threw an electronic ignition set up into it and had to run a more powerfull coil and the bigger gapped and resistor type plugs but for a standard ignition you can't do that cause it wont run right cause the spark will be slightly delayed.

Either way if there fouling up and obviously caused by the oil entering the combustion chamber you have to change the plugs more frequantly or fix the issue.

So it wouldnt be a good idea to mix up the plugs as it wont run right guaranteed

[lexsmaz]

There is no way you will notice on a temp gauge what sort of heat range plug you are running & as OC mentioned its the same range that you are currently running just a bigger gap ..

I would suggest even running a slightly smaller gap than .8mm as it may ? last a little longer, as the spark will just find the easiest path & if you have a big gap its more likely to track down the centre electrode once oiled up, but as suggested change them more often or fix the issue ..

[allencr]

Spark plug Non-Foulers
https://www.dormanproducts.com/cgi-b...p1&vtime=86185

I cannot comment on their usefulness.
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Also, I do not believe that any change of heat range, gap or ignition system, unless the previous was running very bad, will have an observable affect on the engine's temp.

[petergoudie]

Mixing plugs can be done on standard engines from new by the manufacturer. If some cylinders run hotter they might change the plug. Some v-twin motor cycles run different plugs and the V6 mitsubishi magna has different plugs on the front bank than the rear bank.

[JustCallMeOrlando]

Although the Magna is solely because they were too cheap to fit platinums to the cylinders that were easy to change

[MR22ZZ]

most FWD V6s are like that.

They use platinum or Iridium plugs for the rear bank because it's a PITA to access them and run coppers of the same spec in the front bank. It's not exactly mixing plugs though as they are the same temp rating, same spark pattern, and same gapping.

[petergoudie]

On my Mitsu V6 the plugs are different even if you fit non-platinium. If you fit platinum they are the same I presume because they have a wider heat range (that's what they tell me.)

[Tham]

Thank you for all the good info and advice, everyone.

Will certainly look into them all.

My engine has electronic ignition, bought from a salvage
yard. One of the common ones meant for the 5K and also
used in the Starlet's 4K-E in the USA. I believe the coil is
a higher output type.

It's not so much the heat range of the plug, but as TRD-12A
suggested, I believe the larger gap of the BP5ES-11 enables it
to fire a bigger and hotter spark from the electronic ignition.
The engine definitely ran hotter after I installed them.

I'm using back the ordinary BP5ES with 0.8 mm (or .032 inch)
gaps. I take out the fouling plugs and flush out the groove
around the ceramic insulator with carburettor cleaner, every
two weeks. I also use the thinnest Allen key to dig out any
carbon sludge and soot from inside there.


The engine already was running quite hot before this, though.
What happened was, the mechanic opened the radiator cap,
saw a tiny bubble floating floating to the top every now ant
then, and said my head gasket had blown.

I followed his advice and allowed him to replace the gasket.
What I didn't know was that he took the head to the machiners
to have it skimmed. I don't think it was warped (or even leaking).
It seems to be standard practice amongst some mechanics here
to skim the head each time the gasket is replaced.

Well, the higher compression after that inevitably led to
the engine running hotter. With the ambient daytime temperatures
in Malaysia these days, overheating is all too easy, especially
for older rear wheel drive engines with slow belt fans.
I think the compression after the skimming must have shot past
10 to one.

And I think the higher compression deteriorated the piston
rings and valve seals faster than usual.

Talk about having more health problems after going for
unnecessary surgery !

The car aircon man said he could replace the belt fan with an
electric one (running continuously, since there is no thermosat).
He found one with two speeds, meant for Volvos. He said
I could switch to the higher speed anytime, with a manual
two-way switch on the dashboard, if I got caught in a traffic jam
and the engine wanted to overheat. Been lucky so far not
to have the gauge shoot into the red zone so far though,
(try my best to avoid jams), so I still haven't installed the fan
motor yet, but I think it's a matter of time.

And after installing the electronic ignition, it ran hotter still,
presumably due to the higher voltage from the high output
coil firing a hotter spark.

[af300e]

There is no way you will notice on a temp gauge what sort of heat range plug you are running

This sounds about right to me. Unless the plug heat number is so wrong that it's not losing enough heat between cycles and causing pre-ignition??

If it's running hotter after changing only to elec ignition and nothing else then you've ended up with more advance or something.

And those who recommended the iridium plugs have a good point. The electrode tips are tiny, less likely to collect carbon and the point propagates a spark nicely. I cured a fouling issue in a 2 stroke motorcycle this way.

[Dazza]

It could be a warped inlet manifold causing your problems. I have had this happen on 2 Hilux engines. If the manifold doesn't seal properly where it bolts up to the head you will have a couple of cylinders running leaner than the other 2. I just refaced the manifolds by laying a sheet of wet and dry sandpaper on a piece of glass and rubbing the manifold over it until flat. Normally if the inlet manifold is warped the motor will backfire when slowing down or rolling down a hill.

[lexsmaz]

If you are noticing it running hotter after the head & ignition system fitted but doesn't ping i would suspect that the ignition timing is actualy retarded which will make it run hotter ..