My CJ began running rough last week, and I pulled the plugs to see what the
trouble was. I need new plugs, but it was running so poorly, I resorted to a
"trail fix" to see if the valves were still intact. (the valves are fine, I
think)

Anyway, the #3 and #4 plugs had heavy loads of build up on them. The 3 plug
was black and the 4 plug was light gray, all of the other plugs were clean
as a whistle. The build up on both plugs cleaned off easily, and the problem
went away immediately when the cleaned plugs were put back in -- the essence
of a Trail Fix is to take something off, have a beer, and put it back on
then see if all is well with the universe again.

My question is, what does Light Gray, and Black mean as they relate to
deposits on spark plugs? I'm thinking the black plug is telling me that a
valve guide/seal is going/gone, but I'm not sure what the gray plug means.
The build up was pretty large (it fouled the plugs to the point of them not
working), but the mass was not that great. The stuff was pretty light and
flaky, and came off with small knife. I probably could have removed the crap
with my finger nail, or the cap from a beer bottle, if I had to.


Points of Interest
I basically only use my Jeep to drive around town, and I use 3rd or 4th when
I might still be able to use 2nd -- I tend to lug the motor is what I'm
saying. I tend to time my stop sign approach for a minimal (if any) full
stop, and then start out again in 3rd, then short-shift into 4th when I get
to about 20ish.

I seldom get on the freeway, so my speed is generally below 50ish.

Unless wheeling in heavy sand, the power that I pour on is minimal, so I
think I should be suing Cold Plugs as opposed to hot ones. These particular
plugs were bought when I was doing more time on the freeway, and they may be
a step hotter than the stock plugs. I'm thinking that I should go with the
stock plugs when I replace them, or go with the one step colder on the
range. Opinions? Why do I care about hot or cold plugs anyway?

 

Jeff Strickland did pass the time by typing:

> My question is, what does Light Gray, and Black mean as they relate to
> deposits on spark plugs? I'm thinking the black plug is telling me that a
> valve guide/seal is going/gone, but I'm not sure what the gray plug means.
> The build up was pretty large (it fouled the plugs to the point of them not
> working), but the mass was not that great. The stuff was pretty light and
> flaky, and came off with small knife. I probably could have removed the crap
> with my finger nail, or the cap from a beer bottle, if I had to.

Black is an indication of fouling which can be as you suspect a leaky valve guide.
Throw a vac gauge on the engine and watch what it does.
http://www.centuryperformance.com/vacuum.asp

It can also indicate too cool of a plug range, a bad sparkplug wire that
results in a poor burn and excess buildup, or a leaky injector.
How old are the wires?

Light grey is fine, that's usualy fuel deposits from additives.
I like this site, good pics and writeups.
http://www.nightrider.com/biketech/spkplghnbook.htm

> Points of Interest
> I basically only use my Jeep to drive around town, and I use 3rd or 4th when
> I might still be able to use 2nd -- I tend to lug the motor is what I'm
> saying. I tend to time my stop sign approach for a minimal (if any) full
> stop, and then start out again in 3rd, then short-shift into 4th when I get
> to about 20ish.

Lugging will cause buildup. Sounds like you need to get out and give it a
Ferrari tune-up. :)

> I seldom get on the freeway, so my speed is generally below 50ish.
>
> Unless wheeling in heavy sand, the power that I pour on is minimal, so I
> think I should be suing Cold Plugs as opposed to hot ones. These particular
> plugs were bought when I was doing more time on the freeway, and they may be
> a step hotter than the stock plugs. I'm thinking that I should go with the
> stock plugs when I replace them, or go with the one step colder on the
> range. Opinions? Why do I care about hot or cold plugs anyway?

Read this.
http://www.dansmc.com/sparkplugs1.htm

The heat range you should use is the one that is indicated in your service book
unless you have a special application. I have to run one range cooler to prevent
detonation at higher comression levels.


--
-- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!

 

Jeff Strickland did pass the time by typing:

> My question is, what does Light Gray, and Black mean as they relate to
> deposits on spark plugs? I'm thinking the black plug is telling me that a
> valve guide/seal is going/gone, but I'm not sure what the gray plug means.
> The build up was pretty large (it fouled the plugs to the point of them not
> working), but the mass was not that great. The stuff was pretty light and
> flaky, and came off with small knife. I probably could have removed the crap
> with my finger nail, or the cap from a beer bottle, if I had to.

Black is an indication of fouling which can be as you suspect a leaky valve guide.
Throw a vac gauge on the engine and watch what it does.
http://www.centuryperformance.com/vacuum.asp

It can also indicate too cool of a plug range, a bad sparkplug wire that
results in a poor burn and excess buildup, or a leaky injector.
How old are the wires?

Light grey is fine, that's usualy fuel deposits from additives.
I like this site, good pics and writeups.
http://www.nightrider.com/biketech/spkplghnbook.htm

> Points of Interest
> I basically only use my Jeep to drive around town, and I use 3rd or 4th when
> I might still be able to use 2nd -- I tend to lug the motor is what I'm
> saying. I tend to time my stop sign approach for a minimal (if any) full
> stop, and then start out again in 3rd, then short-shift into 4th when I get
> to about 20ish.

Lugging will cause buildup. Sounds like you need to get out and give it a
Ferrari tune-up. :)

> I seldom get on the freeway, so my speed is generally below 50ish.
>
> Unless wheeling in heavy sand, the power that I pour on is minimal, so I
> think I should be suing Cold Plugs as opposed to hot ones. These particular
> plugs were bought when I was doing more time on the freeway, and they may be
> a step hotter than the stock plugs. I'm thinking that I should go with the
> stock plugs when I replace them, or go with the one step colder on the
> range. Opinions? Why do I care about hot or cold plugs anyway?

Read this.
http://www.dansmc.com/sparkplugs1.htm

The heat range you should use is the one that is indicated in your service book
unless you have a special application. I have to run one range cooler to prevent
detonation at higher comression levels.


--
-- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!

 

Jeff Strickland did pass the time by typing:

> My question is, what does Light Gray, and Black mean as they relate to
> deposits on spark plugs? I'm thinking the black plug is telling me that a
> valve guide/seal is going/gone, but I'm not sure what the gray plug means.
> The build up was pretty large (it fouled the plugs to the point of them not
> working), but the mass was not that great. The stuff was pretty light and
> flaky, and came off with small knife. I probably could have removed the crap
> with my finger nail, or the cap from a beer bottle, if I had to.

Black is an indication of fouling which can be as you suspect a leaky valve guide.
Throw a vac gauge on the engine and watch what it does.
http://www.centuryperformance.com/vacuum.asp

It can also indicate too cool of a plug range, a bad sparkplug wire that
results in a poor burn and excess buildup, or a leaky injector.
How old are the wires?

Light grey is fine, that's usualy fuel deposits from additives.
I like this site, good pics and writeups.
http://www.nightrider.com/biketech/spkplghnbook.htm

> Points of Interest
> I basically only use my Jeep to drive around town, and I use 3rd or 4th when
> I might still be able to use 2nd -- I tend to lug the motor is what I'm
> saying. I tend to time my stop sign approach for a minimal (if any) full
> stop, and then start out again in 3rd, then short-shift into 4th when I get
> to about 20ish.

Lugging will cause buildup. Sounds like you need to get out and give it a
Ferrari tune-up. :)

> I seldom get on the freeway, so my speed is generally below 50ish.
>
> Unless wheeling in heavy sand, the power that I pour on is minimal, so I
> think I should be suing Cold Plugs as opposed to hot ones. These particular
> plugs were bought when I was doing more time on the freeway, and they may be
> a step hotter than the stock plugs. I'm thinking that I should go with the
> stock plugs when I replace them, or go with the one step colder on the
> range. Opinions? Why do I care about hot or cold plugs anyway?

Read this.
http://www.dansmc.com/sparkplugs1.htm

The heat range you should use is the one that is indicated in your service book
unless you have a special application. I have to run one range cooler to prevent
detonation at higher comression levels.


--
-- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!

 

If you have the 258 engine, that can mean your wires are getting bad. 3
and 4 cross each other and can short together. If you use a spray mist
of water in the dark when it is running, you can see if that is the
trouble.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Aug./05 http://www.imagestation.com/album/in...?id=2120343242
(More Off Road album links at bottom of the view page)

Jeff Strickland wrote:
>
> My CJ began running rough last week, and I pulled the plugs to see what the
> trouble was. I need new plugs, but it was running so poorly, I resorted to a
> "trail fix" to see if the valves were still intact. (the valves are fine, I
> think)
>
> Anyway, the #3 and #4 plugs had heavy loads of build up on them. The 3 plug
> was black and the 4 plug was light gray, all of the other plugs were clean
> as a whistle. The build up on both plugs cleaned off easily, and the problem
> went away immediately when the cleaned plugs were put back in -- the essence
> of a Trail Fix is to take something off, have a beer, and put it back on
> then see if all is well with the universe again.
>
> My question is, what does Light Gray, and Black mean as they relate to
> deposits on spark plugs? I'm thinking the black plug is telling me that a
> valve guide/seal is going/gone, but I'm not sure what the gray plug means.
> The build up was pretty large (it fouled the plugs to the point of them not
> working), but the mass was not that great. The stuff was pretty light and
> flaky, and came off with small knife. I probably could have removed the crap
> with my finger nail, or the cap from a beer bottle, if I had to.
>
> Points of Interest
> I basically only use my Jeep to drive around town, and I use 3rd or 4th when
> I might still be able to use 2nd -- I tend to lug the motor is what I'm
> saying. I tend to time my stop sign approach for a minimal (if any) full
> stop, and then start out again in 3rd, then short-shift into 4th when I get
> to about 20ish.
>
> I seldom get on the freeway, so my speed is generally below 50ish.
>
> Unless wheeling in heavy sand, the power that I pour on is minimal, so I
> think I should be suing Cold Plugs as opposed to hot ones. These particular
> plugs were bought when I was doing more time on the freeway, and they may be
> a step hotter than the stock plugs. I'm thinking that I should go with the
> stock plugs when I replace them, or go with the one step colder on the
> range. Opinions? Why do I care about hot or cold plugs anyway?

 

If you have the 258 engine, that can mean your wires are getting bad. 3
and 4 cross each other and can short together. If you use a spray mist
of water in the dark when it is running, you can see if that is the
trouble.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Aug./05 http://www.imagestation.com/album/in...?id=2120343242
(More Off Road album links at bottom of the view page)

Jeff Strickland wrote:
>
> My CJ began running rough last week, and I pulled the plugs to see what the
> trouble was. I need new plugs, but it was running so poorly, I resorted to a
> "trail fix" to see if the valves were still intact. (the valves are fine, I
> think)
>
> Anyway, the #3 and #4 plugs had heavy loads of build up on them. The 3 plug
> was black and the 4 plug was light gray, all of the other plugs were clean
> as a whistle. The build up on both plugs cleaned off easily, and the problem
> went away immediately when the cleaned plugs were put back in -- the essence
> of a Trail Fix is to take something off, have a beer, and put it back on
> then see if all is well with the universe again.
>
> My question is, what does Light Gray, and Black mean as they relate to
> deposits on spark plugs? I'm thinking the black plug is telling me that a
> valve guide/seal is going/gone, but I'm not sure what the gray plug means.
> The build up was pretty large (it fouled the plugs to the point of them not
> working), but the mass was not that great. The stuff was pretty light and
> flaky, and came off with small knife. I probably could have removed the crap
> with my finger nail, or the cap from a beer bottle, if I had to.
>
> Points of Interest
> I basically only use my Jeep to drive around town, and I use 3rd or 4th when
> I might still be able to use 2nd -- I tend to lug the motor is what I'm
> saying. I tend to time my stop sign approach for a minimal (if any) full
> stop, and then start out again in 3rd, then short-shift into 4th when I get
> to about 20ish.
>
> I seldom get on the freeway, so my speed is generally below 50ish.
>
> Unless wheeling in heavy sand, the power that I pour on is minimal, so I
> think I should be suing Cold Plugs as opposed to hot ones. These particular
> plugs were bought when I was doing more time on the freeway, and they may be
> a step hotter than the stock plugs. I'm thinking that I should go with the
> stock plugs when I replace them, or go with the one step colder on the
> range. Opinions? Why do I care about hot or cold plugs anyway?

 

If you have the 258 engine, that can mean your wires are getting bad. 3
and 4 cross each other and can short together. If you use a spray mist
of water in the dark when it is running, you can see if that is the
trouble.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Aug./05 http://www.imagestation.com/album/in...?id=2120343242
(More Off Road album links at bottom of the view page)

Jeff Strickland wrote:
>
> My CJ began running rough last week, and I pulled the plugs to see what the
> trouble was. I need new plugs, but it was running so poorly, I resorted to a
> "trail fix" to see if the valves were still intact. (the valves are fine, I
> think)
>
> Anyway, the #3 and #4 plugs had heavy loads of build up on them. The 3 plug
> was black and the 4 plug was light gray, all of the other plugs were clean
> as a whistle. The build up on both plugs cleaned off easily, and the problem
> went away immediately when the cleaned plugs were put back in -- the essence
> of a Trail Fix is to take something off, have a beer, and put it back on
> then see if all is well with the universe again.
>
> My question is, what does Light Gray, and Black mean as they relate to
> deposits on spark plugs? I'm thinking the black plug is telling me that a
> valve guide/seal is going/gone, but I'm not sure what the gray plug means.
> The build up was pretty large (it fouled the plugs to the point of them not
> working), but the mass was not that great. The stuff was pretty light and
> flaky, and came off with small knife. I probably could have removed the crap
> with my finger nail, or the cap from a beer bottle, if I had to.
>
> Points of Interest
> I basically only use my Jeep to drive around town, and I use 3rd or 4th when
> I might still be able to use 2nd -- I tend to lug the motor is what I'm
> saying. I tend to time my stop sign approach for a minimal (if any) full
> stop, and then start out again in 3rd, then short-shift into 4th when I get
> to about 20ish.
>
> I seldom get on the freeway, so my speed is generally below 50ish.
>
> Unless wheeling in heavy sand, the power that I pour on is minimal, so I
> think I should be suing Cold Plugs as opposed to hot ones. These particular
> plugs were bought when I was doing more time on the freeway, and they may be
> a step hotter than the stock plugs. I'm thinking that I should go with the
> stock plugs when I replace them, or go with the one step colder on the
> range. Opinions? Why do I care about hot or cold plugs anyway?