Thread: Spark Plugs and Engine Conditions

Spark plugs provide a bird’s eye view as to what is going on inside the engine and combustion chamber. Usually, the number 1 plug in the firing order is the best plug used to aid in diagnosing conditions. Spark plug changing intervals vary, so check with your engine and or plug manufacturers for specific miles or hours to change them out. Here are some examples of conditions to look for in a spark plug.

Normal- Brown to Grayish tip and slight electrode wear. Can be cleaned and regapped.

Carbon Deposits- Dry black fluffy soot. Indicates a rich mixture, poor ignition, excessive idling, or bad air filter. Can be cleaned.

Oil Deposits- Oily wet black deposits. Caused by oil leaking past rings, excessive clearance between valve guides and stems, or worn bearings. Can be cleaned.

Overheating- Blistered white or light gray insulator with blueish burnt electrodes. Caused by overheating, incorrect timing, or lean mixture. Replace plug.

Ash Deposits- Light brown to white deposits covering the tip and or electrode. Caused by fuel additives or oil entering chamber. Can be cleaned.

Detonation- Melted electrodes or blistered insulator. Metallica deposits indicate engine damage. Incorrect timing, lean mixture, burnt valves, or engine overheating. Replace plug.

Worn- Severely eroded and worn electrodes. Indicates normal wear. Replace plug.

Good info. Pictures for some of the more "mechanically challenged" would be a nice touch...

I'm lucky I have internet at home right now. Your right though.

Thanks for the information. Answers some questions over the years.

this is what you guys are looking for

http://www.ngksparkplugs.com/tech_su...qs/faqread.asp

Ara and Newman, thanks for sharing this valuable info. We sometimes forget to check the sticky's. thanks Wayne aka spotman

I wanted to change plugs in my van the other day, so I removed the doghouse on a 2002 Ford E-350. I couldn't find the plugs so I went to the Internet. I have a 5.4L v-8 which has aluminum heads and the plugs when removed usually bring along the threads which causes the need for a threded steel sleeve. I have 145000 miles on it I bought it new, it has never been hot and is running fine so I'm leaving them alone. Ford won't do anything about this. The Plugs come out the top of the engine which is not very much space. I have a friend that has a pickup and it cost him $250.00 for 2 plugs removed and installed

Originally Posted by ultracleaning

I wanted to change plugs in my van the other day, so I removed the doghouse on a 2002 Ford E-350. I couldn't find the plugs so I went to the Internet. I have a 5.4L v-8 which has aluminum heads and the plugs when removed usually bring along the threads which causes the need for a threded steel sleeve. I have 145000 miles on it I bought it new, it has never been hot and is running fine so I'm leaving them alone. Ford won't do anything about this. The Plugs come out the top of the engine which is not very much space. I have a friend that has a pickup and it cost him $250.00 for 2 plugs removed and installed

The problem is the longer you leave them in the greater the chance of this happening. All aluminum heads suffer from this issue if the plugs are not change regularly as steel tends to seize into aluminum.

I have a 5.4 in my Ford Expedition and blew a plug out, threads and all! As stated above plugs are a "bear" to remove , cost 250 to have 1 hole repaired, without head removal. 185000 miles on it now and no more problems.