Spark Plugs Color interpretation

[Yves]

Hello guys,
need opinion about color disparity of my spark plugs,
SP 1-2 are more brown red then 3-4.
How do you interpret spark plugs color ?

Thanks

 

[Simon Oaten]

download the "older" NGK catalogue......

check if the heat range is somewhere near right.......

compare your plug - with the chart in the NGK book !

 

[NEG]

Over rich mixture and burning oil on 3 & 4 check temperature rating, fuelling, airfilter condition etc.

 

[Dan Sarandrea (Phila)]

Sorry to say that none look good. As NEG posted, two are rich and two are wet, which could be oil fouling. If all were wet like the two, one could say maybe too much blowby from worn rings. When not all show oil fouling, then that calls into question the integrity of the valve stem seals on those two cylinders.

 

[lookforjoe]

Might be time to pull the injectors and have them flow tested also.

 

[rjplenter]

Agree with NEG.

 

[Yves]

Ok not sound good ...
The motor pull hard, the iddle is smooth, start a quart turn, cold or hot, no smoke when I start or running, Oil level never go down ...
But the bottom of the motor have never be touch!, original pistons rings, bearing etc...

Probably pistons rings start to be tired, I redone the injectors 8 years ago, maybe they need again to be test and cleaning.

It is possible the motor running to cold ? Most of time the motor temp is under 190 F (90 C) ... around 175-180 F ... I have a cooler thermostat.

 

[NEG]

That’s a possibility but it doesn’t explain the oil fouling

 

[lookforjoe]

Leak down test would help determine if or where you have leakage/blowby. I wouldn't even think about taking it apart without much more investigation.

Reduced running temp would not explain it, IMO. How many miles do you drive it when you take it out? Does it routinely have time to reach full operating temp, or do you have a fair amount of stop/start short drives?

Like Simon said - plug type, gap & heat range could also factor in the rich burn. Maybe try some plain WR7DC & see if it makes a difference to that condition?

 

[carl]

I hate to sound like the voice of reason, but your explanation of how your motor is running makes it sound like you have a perfectly fine running motor and if you hadn't pulled the plugs you would never know there might be an issue. How long have the plugs been in there? How old is the oxygen sensor Do you want to take apart a perfectly fine running motor and start throwing money at it?

 

[Yves]

Carl,
no I don't take apart when I don't have more symptom then only Spark plugs symptom.
The car is running very well.
Even on a long distance the temp is lower then 190 F (Cooler thermostat and ALU radiator)

The Oxygen sensor was replaced about 18 months same thing for the spark plugs.
Air Filter is perfectly clean.

This is what I will do this winter to try to attenuate the spark plugs symptom...
Put back Savara original thermostat (I have in stock a brand new one).
Change the spark plug for NKG BPR6ES.
If I have time I will pull out the fuel rail and check the injectors spray pattern.

Three years ago when I have replaced my original head by a MWB performance Head I have play with the sealed screw adjustment
on the AFM ... I will check again.

The worst case is the color of spark plugs will stay same, in that situation it is sure I will wait until others symptoms will appear in parallel.
I will not open the bottom motor just for a not perfect coloration of spark plugs when the motor running well without any other issue.

I will not throw out my money just for spark plugs coloration!

Yves

 

[Dr.Jeff]

I agree with your thoughts Yves. Maybe I'd do compression and leak down tests just as routine checks, for peace of mind. And I'd service things; tune up, etc. I do not think the engine temps you mentioned are anywhere near too cold. In fact that was considered high temp back in the era these cars were first designed. I've never experimented with any multiple electrode plugs like you have. I have found (generally speaking) that some engines seem to do much better with certain plugs overs others, and vice versa. As peculiar as it may sound, perhaps the SOHC does not do as well with those multi electrodes types? Also check over the rest of your ignition system just to make sure everything is functioning properly. Same with the EFI system. The comments about injector servicing reminded me of a very interesting discussion I recently had with the engineer from "GB", the company that rebuilds fuel injectors. I'll add something to my thread about the SEMA Show in the NFC section to relay what was said.

I can't resist; what brand of oil are you using? Only joking...my comment about the plugs was bad enough, lets not start one of those debates again.

 

[Yves]

I agree with your thoughts Yves. Maybe I'd do compression and leak down tests just as routine checks, for peace of mind. And I'd service things; tune up, etc. I do not think the engine temps you mentioned are anywhere near too cold. In fact that was considered high temp back in the era these cars were first designed. I've never experimented with any multiple electrode plugs like you have. I have found (generally speaking) that some engines seem to do much better with certain plugs overs others, and vice versa. As peculiar as it may sound, perhaps the SOHC does not do as well with those multi electrodes types? Also check over the rest of your ignition system just to make sure everything is functioning properly. Same with the EFI system. The comments about injector servicing reminded me of a very interesting discussion I recently had with the engineer from "GB", the company that rebuilds fuel injectors. I'll add something to my thread about the SEMA Show in the NFC section to relay what was said.

I can't resist; what brand of oil are you using? Only joking...my comment about the plugs was bad enough, lets not start one of those debates again.

Jeff, the oil I use is Shell Rotella T4 15-40,
Yes I will check the compression and do a leak down tests. Last winter the compression was between 160- 170 on all cylinders.

But it is sure somewhere in the future I will need to do the bottom of the motor ... the plugs is a sign and normal after 34 years.

Thanks everybody for your feed of informations and opinions.

Yves

 

[Yves]

Leak down test would help determine if or where you have leakage/blowby. I wouldn't even think about taking it apart without much more investigation.

Reduced running temp would not explain it, IMO. How many miles do you drive it when you take it out? Does it routinely have time to reach full operating temp, or do you have a fair amount of stop/start short drives?

Like Simon said - plug type, gap & heat range could also factor in the rich burn. Maybe try some plain WR7DC & see if it makes a difference to that condition?

Hi Hussein, I use the car every weekend when is not raining, it is a mixture of local driving and some highway. The highway is a minimum of 15 minutes, sometimes 45 min. Enough long to ramp up the temperature to the normal, in my case around 175-180 F. The traveling average mileage on a weekend is about 30-45 miles.

 

[Yves]

Follow up …

Today I made a leak down test and compression test.
Compression, all cylinder are between 170 180.

The leak down test reveals the entire cylinders leak by cylinders rings, but not excessively. The two worst for leaking test is cylinder 1 and 2. Spark plugs 1 and 2 show by the coloration like they are too much rich, and 3 and 4 like contamined by oil... But the the leak down test showing is 1 and 2 was not tight compare to 3 and 4, I can hear the hiss by the bottom, I was suprised. My next step is to check all injectors for the spray pattern, maybe they will show the injectors 3 and 4 have something wrong ... to be continued.

Yves

 

[EricH]

Spark plugs 1 and 2 show by the coloration like they are too much rich, and 3 and 4 like contamined by oil... But the the leak down test showing is 1 and 2 was not tight compare to 3 and 4,

Sounds like the valve stem seals for 3 and 4 are letting oil in.

 

[Yves]

Sounds like the valve stem seals for 3 and 4 are letting oil in.

Maybe, but when I start the car even after a long period without running they never smoke. Also the Head is only 3 years old (MWB Performance head).