Please have a look at this video and tell me your thoughts. Number 4 is a bit sooty and these were changed 1,000 miles ago. I am using NGK BKR 6ES. Number 4 is a BPR 6ES for some reason I can not remember as the only difference is the hex size.
Gerard
All but #4 look about right to me, maybe a bit on the lean side. #4 looks like oil fouling.
I’ll be interested to hear what others think.
Agree - little lean, oil on the number 4. I have the same issue with my number 4 fouling a little. Only matters if I start up and shut down without the plug having a chance to get properly hot. 25% of the time necessitates pulling it, cleaning it and putting back in. Other than that I lived with it for the last 10 years.
Dave
I wonder if the factory heads all needed a bit of porting to clean up the area on the number four plug? I will have the A/F/ mixture re-analyzed to solve this possible leaning out problem. How often do most people change their plugs? I am giong to bump up to a 195 degree F T-stat and see if this also solves the fouling problem. I don’t use the bellows t-stat (Read MUCH cheaper) as I have a bypass plug installed which keeps my cooling too cool if anything.
Here is a video of this if anyone needs a description of the plug.
Gerard
If everything else with your cooling system is working, you might consider a one step hotter plug for #4 and see if that makes a difference.
Dean
Has the engine always done this? Has the engine been rebuilt? How old are the cap and wires?
I’d be inclined to do a compression and a leakdown test.
Had a complete balance and blueprint done just 10,000 miles ago. I am running the same Petronix dizzy and magnecor wires for that entire time. I wonder what running a hotter plug on that one cylinder would do? I will check this plug after running through the warmer weather coming up this Summer and having the engine running at the proper temperature.
I can do a compression test but that will have to wait for warmer weather as I don’t have the inddor space to handle that test.
Anybody else having a single cylinder fouling problem like this?
Gerard
In your initial post it seems the onl plug that is different is a plug that is different! I understand your belief that they are the same except hex drive but the first thing I would do is put a matching set of plugs in and re try, Perhaps the one plug is NOT the same!
The set I just installed is all the same. I believe I was having misfiring problems on number four (4) awhile back and just changed that one plug (albeit with the different hex). They are all on an equal playing field now and I will watch them for more sooting. The car runs fantastic but just eats gas. i.e. 12 mpg US
Once a jewel in the picture, not sure where this car is.
Gerard
Perhaps someone with extensive knowledge of the cooling paths of the 3.8 might point out that the number 4 cylinder receives more or perhaps less cooling than other pistons thus causing sooting on the #4 plug?
Gerard
