Spark plug carbon say its time for first ARX!

[Jim Spahr]

I just changed my platinum Bosch spark plugs on a Chev LT1 V8. At 27.3k the plugs were starting to show carbon build up around the threaded end. This is a dark color and I can imagine it inside the cylinder andcoating the rings as well. I think it must be time for me to break down and try Auto RX for the first time to see if it works on a Chevy 350". Do you think that Auto RX will help this type carbon build up?

 

[unDummy]

If it is oil burning related? How much oil is getting past the valve seals? piston rings?

I think that maybe you should check your electromechs 1st. Hows the a/f ratio? o2 sensor? map/maf? intake(airfilter)/exhaust(catclogged)? any other components? temp/speed/tps/thermostat......?

I'd also consider a FI service to make sure that all injectors are also squirting the same.

 

[Jim Spahr]

The engine has 197k miles. I just changed both O2 sensors for the first time about 3k ago. I run a bottle of Techron by Chevron about every 15k. The air filter is changed at 12k. The cats are not a problem. With 10w30 I was seeing about 1 qt every 1500. Recently I went to 5w30 and saw a significant increase in oil consumption: 1 1/2 qts. at 1000 miles. Of course, I plan to go to a heavier oil-like 15w/40- next oil change which will coincide with the warmer weather.

 

[theguru]

I will suggest a couple of things.
/ The spark plugs are worn out. Some just don't last too long, even platinum. I use NGK personally. Or maybe these just don't suit this motor or wrong heat grade.

2. If its oil related the spark plug end will show up with very little driving. Put in a new set and check them after a few days. Maybe do a compression test. You can probably have a look in the spark plug hole either directly or with a mirror to see carbon build up on the piston.

Thicker oil will also help. If you are using oil, other than by leakage, then some is going to be left behind as carbon.

 

[Rick20]

I think ARX will help, if the ring packs are carboned up. Poor ring seals, less than optimum compression, promotes a poor burn. Worth a shot.
May want to consider running a shot FP or other fuel system cleaner as well. Then put in the new plugs.

 

[Jim Spahr]

First , to clarify. The tips of the old platinum Bosch plugs were whitish with some dry carbon build up. What I was trying to describe was the reddish brown carbon build up on the end of the threaded portion of the spark plugs. These were very dry and reddish brown, not wet black deposits like heavy oil burning causes. Here's an update. I did change the plugs with new Bosch platinum plugs. I did change the oil and filter going to a heavier 15w/40 Penzoil and the good old Delco PF 52. Now I have started the Auto Rx Cleaning Phase and have the 1500 miles to go. I will report the results at the next oil change.

 

[theguru]

What you are describing may be normal in this car as the base of the plug does run at a different teperature and it usually the tip that is examined.

Reddish/ brown deposits can aslo be caused by fuel additives, such as octane boost, and also coolant/ water ingress.