I probably know the answer to this problem but be that as it may.

My mileage is not high. Last long trip was circa 2k a year ago, since then just short trips with the longest return 80km.

I put new plugs NGK BKR5E before that long trip. I’m doing a service now and pulling plug to clean I’m surprised just how dirty they are. Motor runs perfectly, no blue smoke other than start up from cold and doing a start up Rev bit of black exhaust can be evidenced on concrete drive at exhaust end. Plugs would have done say 3k miles.

I use Morey’s Upper Cylinder lubricant & injector lubricant as per instructions per litre of fuel. Fuel is 95 octane Change oil every 2k. Oil is clean as per dip stick. My query for discussion is am I using correct plugs. Acknowledge that short trips that do not get engine hot enough could be a cause.

This is my first Classic with injectors.
any comments from you learned folk appreciated.

mike

 

Don't know if those are the right plugs or not.

With fuel injection your plugs really should stay clean even if you make short trips. I often drive only 5 miles/day, day after day, and my 5 year old plugs looked great when I changed them recently

You might wanna start investigating the possibility of an over-fueling situation.

I also wonder if the additives might be blackening the plugs?

Cheers
DD

 

How much oil are you actually burning? Have you checked/measured?

Cheers
DD

 

The early 3.6 cars have a known over richness problem as described here: A COMMON PROBLEM WITH THE EARLY 3.6 XJS (1983-87) / AJ6 Engineering

 

Doug, it may well be the additive. I’m burning no oil. Dip stick oil is clean and I never need to top up between oil changes, it’s got to be fuel.

thanks

mike

 

My NGK Catalogue lists

BCPR6E as the spec, for the AJ6 3.6, 3.2, 4.0 etc.

Same for the AJ16 except the Supercharged engine.

 

Ditch the additive and use only 98 octane and they right plugs and it will clean up!

 

Don't ditch the additive, don't bother with soot on the spark plugs. Every classic car additive, 2stroke or engine oil will give you this effect. The KEY is to have all sprak plugs covered EQUALLY and in the same colour.
Every non-classic car additive will degrade fuel over time, your octane level will go lower and lower if not driven out periodically. That may cause sooting.
If piston rings are tired - will let some oil through - but again - equally. Running rich is good for petrol engine, don't bother with it unless your pocket dries out - if so, buy Suzuki...
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Why you're using 95octane instead of 98 ??? (unless not available in your geographical location...)

 

Owner manual is your friend, says, 98 octane, says it on the middle of the cluster. I only used 98 100% gas. Ethanol is trash, especially if it sets in the tank for awhile.

 

I would love to use 98 Octane but where I live 95 is all I can get. Not too far away I can get 100 Octane, probably the best, but cost is circa 30 cents per litre more than 95. 98 is available in the cities, Wellington my closest but a large water strait inhibits that proposition. and South to Christchurch is 400km away.

Cost of fuel here is bloody expensive. When I lived in QLD Aussie I used to laugh that I was paying $1.30 per litre but back in my homeland it was nigh on $ 2.30. That was 7 years ago. The fuel oil companies just rip us off. ☹️

 

It's actually your government. Most of the price of fuel at the pump is tax. A few years ago I was working for a company that had a bulk fuel account and the invoice for the fuel came monthly and was broken into the cost of fuel and the taxes were added as separate line items. Retail pump price was $1.20/litre and the cost of fuel from the oil company was 29 cents/L. The rest was tax.