Plugs getting progressively burnt, looking for explaination - Honda Prelude Forum

Cruxader · 02-24-2003, 04:00 PM

I just changed the plugs for my friends SS (56k miles, pretty well maintained) and noticed something I've never seen when working on my SH.

Starting from the spark plug nearest the distributor cap to the farthest, his plugs got progressively more burnt. For example, the first plug was almost immaculate - tip had normal wear, but the threads barely had any burn residue. However, the last plug that was pulled out was world of difference. The tip was burnt to white coloring and the threading has 75% covered w/ that black burn residue. So...

Plug:
1 - good
2 - ok, but not as clean as plug 1
3 - ok, but burned somewhat
4 - burnt bad

Any ideas why? Thanks.

71dsp · 02-24-2003, 04:12 PM

Pictures would really help.

Also, check out:

http://www.ngksparkplugs.com/techinf...q/faqread2.asp

http://www.ngksparkplugs.com/techinf...s/overview.asp

apocalypse · 02-24-2003, 11:09 PM

Dry and Wet Fouling
Although there are many different cases, if the insulation resistance between the center electrode and the shell is over 10 ohms, the engine can be started normally. If the insulation resistance drops to 0 ohms, the firing end is fouled by either wet or dry carbon.

whats insulation resistance?

marcucci · 02-25-2003, 09:13 AM

The threads? The threads don't stick in the cylinder (at least not more than the first or second thread) so that doesn't mean anything. Pictures would help a lot here.

If they get progressively whiter that means that those cylinders are progressively more lean. A little white is normal, though, so it may just mean the other cylinders are running more rich.

There's not much you can do other than troubleshoot fuel symptoms. I would start with swapping the injectors from 1-2-3-4 to 4-3-2-1 and watch to see if the plugs change appearance with the injectors. You can also inspect the injectors for fouling/carbon while they are out. Be sure to replace the seals with them out since they typically tear or shrink and might leak (you don't want that to happen). Also change out the crush washers on the fuel line.

H22a_Assasin · 02-27-2003, 12:28 PM

What are his mods?

JmLude02 · 02-27-2003, 06:00 PM

What are crush washers again? i forget these things

marcucci · 02-27-2003, 08:40 PM

Washers that crush and seal upon installation. Can't use them twice, reliably, at least not in high pressure (like fuel or brake) applications.

prelude2005 · 02-28-2003, 07:35 AM

how often do you have to change your plugs, wires, rotor and cap?

Cruxader · 03-02-2003, 10:52 PM

Quote:

Originally posted by 71dsp
Pictures would really help.

Also, check out:

http://www.ngksparkplugs.com/techinf...q/faqread2.asp

http://www.ngksparkplugs.com/techinf...s/overview.asp

Thanks for the info. The worst plug looks like the "normal condition" picture, where as the best plug look like its almost brand new.

I wish we had thought about taking pictures, but unfortunately, he threw them out already.

Cruxader · 03-02-2003, 10:56 PM

Quote:

Originally posted by marcucci
The threads? The threads don't stick in the cylinder (at least not more than the first or second thread) so that doesn't mean anything. Pictures would help a lot here.

If they get progressively whiter that means that those cylinders are progressively more lean. A little white is normal, though, so it may just mean the other cylinders are running more rich.

There's not much you can do other than troubleshoot fuel symptoms. I would start with swapping the injectors from 1-2-3-4 to 4-3-2-1 and watch to see if the plugs change appearance with the injectors. You can also inspect the injectors for fouling/carbon while they are out. Be sure to replace the seals with them out since they typically tear or shrink and might leak (you don't want that to happen). Also change out the crush washers on the fuel line.

That's what his thoughts were too. It does appear that the cylinders are getting progressively leaner or richer - whichever way you want to look at it.

I'll let him know about the injectors swapping idea. Thanks for the tip.