Spark plug diagnosis.

Yeah, your car is running rich or spends most of its life doing short journeys.

Sooty black is the sign of rich running but if you're only doing short

Thanks Conor.

Hmm, I've recently switched from a fairly convoluted 20 mile backroad commute to a simpler 15 mile backroad one.

I don't thrash it mercilessly, but I am a fairly enthusiastic driver and there isn't any traffic so I get up to 50-60mph between the junctions. Looks like it could be running rich to me.

I think I will investigate temperature sensors next.

I've ascertained that the one in the radiator is just a switch for the rad fan.

Senders in the block near the thermostat could be feeds for the ECU, whaddya think?

A dicky thermostat could mean the engine never gets properly warm?

Personally, before I did anything, I would take the car for a nice long run (at least 100 miles) on the nearest motorway at the highest possible legal speed just to get things nice and hot and all the crud cleared off the plugs (and out of the engine oil as well) - and then recheck things.

It's the low, daily mileage that probably causing that - it used to happen on the wife's car and a good, long run once a month would sort it for a while - and it was a chance for a day out as well.

Falco

Perhaps you are right, but in the 20,000 miles and 3 oil changes I've done so far on the car, I've not had the petrol smell in the oil problem.

My new commute only started 2 weeks ago, and I changed the oil about a week before that.

I'll drive to work and back this week in 3rd gear and see what happens. (c:

The nearest motorway can't be much less than 100 miles away, not sure I can be arsed, but I'll try ragging it a bit harder as you suggest.

The plug isn't sooty black. The bit to look at is the INSULATOR not the body of the plug. The insulator is the normal colour for injection cars running unleaded. White with a hint of tan.

Heheh, so you think its fine?

Looks OK to me too. The insulator colour shows that overall it's certainly running hot enough and lean enough.

John

Conor has brought this to us :

It is the plug nose you should be looking at, rather than the inner diameter of the metal body. The nose is clean as a whistle, which on a carb car would suggest it is running weak. However, no wear or burning of the electrodes would suggest it is fine.

"Douglas Payne" wrote

Waste of time. It reduces peak combustion temperature and pressure - unless there is space to get a combination of high revs and wide open throttle.

If it's broken it needs spanners to fix it - driving it won't make it less broken.

If it's 11 years old and broken drive it until it's too broken to go any further because it probably isn't worth fixing.

So long as it starts normally, runs smoothly, returns 40mpg and has spark plugs like the ones in the picture, it probably isn't broken.

Rightyho. Thanks. The gases coming from the oil filler when running do smell awfully of petrol though. Will compare with my other car when I get home tonight.

if it was running rich enough to make the oil diluted with fuel then it would run very badly, it would also fail the mot emissions test in a spectacular way