Spark Plugs Ceramic Discolored

Randeewa · November 13, 2015

Hi

My Chevrolet Cruze 2003 and have a problem and need an expert advise.

The car has an ignition or spark plug like noise on starting at morning. When 10 to 20 minutes driving, it will be disappear (That mean engine got hot). Sometimes load is high and at hills noise come again. My electrician checked it and says spark plugs are faulty because there is yellow line burn marks in the ceramic insulator and needs to be replaced.

The car is 83000Km and electrician says still it has original OEM Denso Iridium Spark plugs.

Are Spark plugs faulty because of ceramic discolored? (Tip is fine)

Do I have to replace Iridium spark plugs at 83000Km?

M13A Suzuki engine and bonnet sticker says spark plugs replace with NGK IFR5J11 or IFR6J11 what are the different between them?.

Your advices is highly appreciated.

Thanks

Rumesh88 · November 13, 2015

That yellow mark usually known as a "Corona Stain" is quite normal and is not a sign of a fault. If your mileage is genuine the plugs may have a life of another few thousand kms left. As for the difference between IFR5J11 and 6J11, these figures specify the heat range of the plug. A 5J11 will have a slightly hotter tip while in operation than a 6J11 and hence is more likely to knock (or go into pre-ignition) but this again depends on the fuel octane number and design of the engine (the market variant). Best thing is to replace with the same plug type that the engine originally came with and use the recommended fuel type.

As for your ignition noise, when was the last time a "tune up" was done? Tune up is basically a clean up of the throttle body and sensors, fuel injectors, and inspections of plugs, scan for stored error codes etc. Also does the engine rev up on cold start and then slow down as the engine heats up as expected? Do you get this noise with the AC off as well?

Randeewa · November 13, 2015

That yellow mark usually known as a "Corona Stain" is quite normal and is not a sign of a fault. If your mileage is genuine the plugs may have a life of another few thousand kms left. As for the difference between IFR5J11 and 6J11, these figures specify the heat range of the plug. A 5J11 will have a slightly hotter tip while in operation than a 6J11 and hence is more likely to knock (or go into pre-ignition) but this again depends on the fuel octane number and design of the engine (the market variant). Best thing is to replace with the same plug type that the engine originally came with and use the recommended fuel type.
As for your ignition noise, when was the last time a "tune up" was done? Tune up is basically a clean up of the throttle body and sensors, fuel injectors, and inspections of plugs, scan for stored error codes etc. Also does the engine rev up on cold start and then slow down as the engine heats up as expected? Do you get this noise with the AC off as well?

Thank you very much for the reply

Yes car is idling fine as you mentioned (engine rev up on cold start and then slow down as the engine heats up) and not any difference in performance. I am running always AC on and after noise came up I have checked with AC off noise is there. Actually my noise is very (100%) similar to the thread I found very recent in AL.

("since last month when i accelerate the car (while driving only)something like engine knock sound("kata kata") something like rattle sound (but not a engine knock) coming from engine after few seconds its vanished.but no any difference with engine performance ..pickup or gear changing.last week i did a engine tuneup & sensors checked .but no luck with that too.my mechanic says he cant predict it tooo because car performance is very well...what should i have to check now?does any one had a similar problem like this?")

He have solved the problem with cleaning/replacing MAF sensor (I have no idea where it located in my car) Car is bought only 4 months ago and I don't have service records. May be the previous owner didn't done engine tune-up recently.

I have a big doubt about replacing spark plugs. thanks for the advice. I am gonna do engine tune-up (Sensors checked) tomorrow straightway as you advised. Please let me know what are the other sensors related to this problem I have to get checked.

Thanks

Rumesh88 · November 13, 2015

After you buy a car if you do not have previous maintenance records, you need to set a maintenance schedule on your own. Get the engine oil and filter changed, ATF changed, wheel alignment checked and a tune up done. Better if you can change other fluids like brake oil and coolant as well. When you get a tune up done make sure they inspect the PCV valve and EGR valve as well. This kind of marginal knocking cannot be traced to a particular sensor but a general tune up should take care of it. As for your MAF it is located on the intake path close to air filter cover.

jczunega · December 13, 2020

sounds like the pistons. could the cylinder walls be worn? or normal. when running the engine at first while at cold temperature there's a clearance/gap between the piston sides and cylinder walls to give way for the pistons thermal expansion at normal operating temperature which would cause the piston to dance hitting the cylinder walls causing the rattling noise but as it gets hotter it expands more until that clearance is no more causing the sound gone and making the engine run smoothly. i think it's normal but if the noise is excessive it could be worn or something.

Edited December 13, 2020 by jczunega

AVANTE · December 13, 2020

22 minutes ago, jczunega said:

sounds like the pistons. could the cylinder walls be worn? or normal. when running the engine at first while at cold temperature there's a clearance/gap between the piston sides and cylinder walls to give way for the pistons thermal expansion at normal operating temperature which would cause the piston to dance hitting the cylinder walls causing the rattling noise but as it gets hotter it expands more until that clearance is no more causing the sound gone and making the engine run smoothly. i think it's normal but if the noise is excessive it could be worn or something.

Its a 5 year old post. Guy must have sold that car by now, who knows.

As for the taka taka sound, it could be engine knock/pinging. Worn out engine/piston rings won't make any such sound because you'll have a hard time trying to start it in the first place.

If it was worn out, It'll smoke like a factory, the dipstick will shoot out at high rpm due to excess blowby, it'll drink oil and fuel like there's no tomorrow and it will struggle to go up a hill or accelerate.