reading spark plugs?

Cyber-Mav

Cyber-Mav

Cyber-Mav

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changed my spark plugs a few months back, the ones I took out the car had white stuff over them
plugs been in the car for around 9 years and done about 35k ish.
no issues with misfiring or bad performance, but have noticed improved fuel economy with the new plugs.

photo below:

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is this normal for worn plugs? does it give any indication of how engines been running?
 
Hmm what causes it to run lean? Iv had the car for 19 years and still drives good. Only mods done to it are an induction kit fitted to it around in 2002. I changed the plugs myself using genuine ford ones in 2007.
Passes emissions test fine?
 
That's from burning a bit of oil, I believe. Could try changing to a slightly heavier grade, or using a higher-quality oil.

Some fuel additives can have a similar effect.
 
ahh, ok yea it used to loose oil but fixed that due to rocker cover gasket leaking. old gasket was brittle and falling apart when I changed it.
iv ran stuff like cataclean and redex in it over the years on those plugs. maybe 35k was too much for them. although ford state to change them every 40k....

this year is the first time iv done the oil change myself, usually get national tyres to do it using voucher discounts. always specified 5w-30 fully synth to them but ya never know what stuff they put in.
used shell 5w30 helix ultra this time fully synthetic done over 2000 miles on it and topped it up to max mark last weekend needed about half a coke cans worth of oil to get back to full mark. should have changed the cam cover gasket years ago!
 
Lashout_UK said:
That's from burning a bit of oil, I believe. Could try changing to a slightly heavier grade, or using a higher-quality oil.

Some fuel additives can have a similar effect.
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I would second that.

A bit of oil burning but otherwise OK.

Mind, having left them in for so long you are lucky to have got them out without them snapping off in the head!

Ignore the service schedules. Change plugs every two years max!

Seized/broken spark plugs can be an expensive PITA, (especially if they are the rear ones on a Merc V8 :eek:)

(And if it is a Ford, change the leads at the same time. For some reason Fords seem to be rather hard on plug leads. If you do not change the leads at the same time one often finds the leads start to track about a month later )
 
yea when removing them they were stiff and making a lot of creaking noises. but I did it slowly and they came out fine.
should the threads be greased up or have oil put on them?
 
Cyber-Mav said:
should the threads be greased up or have oil put on them?
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The "Official" advise is no, the concern is that with lubricated threads it is possible to over tighten them (particularly the taper type)

However, In practice I have been using a bit of copperslip on plug threads without issue for decades.

You just have to be careful not to go all He-Man when you tighten them up :p



It also helps to run a thread chaser (Tap) through the plug threads to make sure they are nice and clean before installing the new plugs, especially if they were tight coming out. This was particularly important on the old Ford Pinto engines, the large coarse plug threads got really mucky, I would always clean those out even if I dont normally with regular threads.

(Put a bit of heavy grease on the tap first so that any debris sticks to it rather than falling into the engine)
 
Cyber-Mav said:
Hmm what causes it to run lean? Iv had the car for 19 years and still drives good. Only mods done to it are an induction kit fitted to it around in 2002. I changed the plugs myself using genuine ford ones in 2007.
Passes emissions test fine?
Click to expand...

My old e38 728i had similar deposits on the plugs,changing the K&N panel filter - which was on the car when I bought it - back to an oem item cured it.
 
odd I thought the ecu should be able to adjust and throw in more fuel to keep the afr correct with a k&n filter preventing it from running too lean?
or is this only something modern cars can do? although mine is not carb, its ecu controlled. ??
now im beginning to wonder if its the k&n induction kit im running causing the engine to run a bit on the warm side under wide open throttle. hmm.....
 
Cyber-Mav said:
odd I thought the ecu should be able to adjust and throw in more fuel to keep the afr correct with a k&n filter preventing it from running too lean?
or is this only something modern cars can do? although mine is not carb, its ecu controlled. ??
now im beginning to wonder if its the k&n induction kit im running causing the engine to run a bit on the warm side under wide open throttle. hmm.....
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Looks more like deposits due to burning oil than running lean, we need to see the lower portion of the insulator . ECUs can make adjustments to fuel trims, but they're limited in the amount they can deviate from the original map and will only adjust while they're running in closed loop.

An induction kit won't have enough effect in Volumetric Efficiency to cause an engine to run that lean (Most cars will run on the richer side of things for safety in extreme climates)

Closed loop only generally occurs at part throttle below ~3000rpm, while in open loop they will use the open loop fuelling table as most are only fitted with a narrowband lambda sensor whereas as Wideband Lambda sensor is required to correct AFRs targeted anything other than stoichiometric (14.7:1 for petrol), it also stops bad sensor feedback potentially causing disaster.

As a good example, the wideband lambda sensor failed on my MX5 failed meaning the gauge reported a constant 22.4:1, had the ECU not been setup with error checking with the sensors controller I'd have found myself dumping a lot of extra fuel into the cylinders.
 
I pulled the plugs and found the deposits, rang the dealer (an Audi specialist!) And their technician asked straight away if I'd fitted a K&N type filter,if not check if it had one,sure enough it did, replacing it cured the deposits (without changing the plugs) and stabilised a slightly lumpy idle,apparently caused by the ecu being confused by the extra airflow of the K&N.

Not what I'd have expected but there you go!

Looked at an e38 740i recently (after a weekend caravan towing toy to ease the pain of my Corsa daily :o) it too had a lumpy idle and popping the bonnet I found a non standard cone filter!
 
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Scania said:
I pulled the plugs and found the deposits, rang the dealer (an Audi specialist!) And their technician asked straight away if I'd fitted a K&N type filter,if not check if it had one,sure enough it did, replacing it cured the deposits (without changing the plugs) and stabilised a slightly lumpy idle,apparently caused by the ecu being confused by the extra airflow of the K&N.

Not what I'd have expected but there you go!

Looked at an e38 740i recently (after a weekend caravan towing toy to ease the pain of my Corsa daily :o) it too had a lumpy idle and popping the bonnet I found a non standard cone filter!
Click to expand...

Odd, no such problems with Cosworth panel filters in dad's Impreza STI and Long term fuel trims were all around 1.5-2% last time I checked them

Come filters will have more of an effect especially if they replace the MAF tube as it changes the air velocity through it meaning the MAF under/over reads
 
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