White Plug, Brown Plug

[echrisconnor]

I've been doing a bunch of tune up projects to my car recently. When I changed plugs, I noticed that they varied significantly in color from one to another. After putting in new plugs and pulling them a week or so later the color difference is still there. I've tried a few things to see what the problem is and can't figure it out. Does anyone know the potential source and whether it is a potential problem?

Here's what I've done recently:
New fuel & air filters
New plug wires
New plugs
New cap & rotor

Yesterday evening, I pulled several of the injectors. There was no perceiveable difference in the spray between the lean and rich cylinders. The car blows some smoke at startup. I've searched for vacuum leaks with carb cleaner and found none.

Any ideas?

[Jim Richards]

valve adjustment?

[echrisconnor]

It probably needs one. Would that make a noticeable difference on plug color?

[Jim Richards]

Forget my earlier, hasty comment.

Are the brown plugs carboned up or oily. Are the white plugs really a tan color or are they pretty white?

[echrisconnor]

Prior to switching plugs (now running bosch platinums), the darker plugs were wet and carboned up pretty well. The lighter plugs were dry and dark brown.

Now, both appear dry. The darker plugs look like a proper mixture; light brown. The electrodes on the light plugs are completely white. There are signs of ingnition with a dark ring around base of the threads.

[Jim Richards]

Check out this old thread for additional ideas

It looks like a similar problem. I hope this helps you out.

[Sean Hamilton]

Originally posted by echrisconnor
Prior to switching plugs (now running bosch platinums........

Are they a hotter plug - now masking the problem?

[QUOTE
......the darker plugs were wet and carboned up pretty well..........[/QUOTE]
Worn valve guides/seals?

[echrisconnor]

They're the same heat range but I went from the standard Bosch to the Platinum (not +4). I think you're on target though with warn valves & guides on top of the need for a valve adjust.

I've also been running through my CIS system finding some problems. My troubleshooting may have have the engine running lean.

[Superman]

Sorry to tell you, ditch the platinum plugs. All of the German car mechanics I have respected over the years, when we've talked about this, report that they routinely replace Bosch plantinum plugs with Bocsh copper any time they find them. There are some early 911s that are treated differently but not your car. Apparently, the copper core plugs work best on almost all engines.

[stlrj]

The insulator tips on all your plugs should remain white. If you don't believe me then pull a plug out of your Mercedes, BMW, Lexus or Infinity and see what color they are. Unless there is something very unusual about our Porsches, our plugs should look the same...or am I missing something?

Joe

[Superman]

In the olden days (here we go again), the porcelain should ideally be tan, and the electrodes should not have white specs on them. Nothing should be caked with oil. In reality, engines are not all brand new, so oil gets on the plugs and they don't all appear the same. And in newer cars, these color recommendations may not be appropriate. I think modern cars run so lean that the porcelain is not even tan. But the white specs are certainly there. White specs are good for the environment, and perhaps good for the newer engine designs, but too lean for the cars of yesteryear.

[Sean Hamilton]

Originally posted by Superman
In the olden days (here we go again), the porcelain should ideally be tan, and the electrodes should not have white specs on them. Nothing should be caked with oil.

Yes, you can tell so much about the health and status of your engine by what the plug is telling you, IF you can interpret their storey.

BUT, my (40 year old) TR is telling me some thing that has me baffled.
The firing order is 1-3-2-4.
1- on the first carburettor,
2- on the 2nd carburettor,
3- back on the first and
4- on the 2nd.
The plugs for 1 & 2 are spot-on Tan,
whilst 3 and 4 are wet and oily.
I doubt therefore it is the carbs but more likely the ignition system, but what?

[stlrj]

modern cars run so lean that the porcelain is not even tan

So, modern cars with the same 02 sensor technology found on our Porsches, having to meet the same emission standards are somehow exempt from the laws of physics and run even leaner than what a three way catalyst is capable of operating?

That's news to me.

The plugs on my 86 Carrera are just as white as the plugs that I pulled from my 92 Grand Caravan, 90 Bonneville, 86 Olds 98. If I found one that was not snow white, I could tell right away which one was the bad plug.

Joe

[Sean Hamilton]

Originally posted by stlrj
modern cars run so lean that the porcelain is not even tan
........02 sensor technology.........a three way catalyst

Isn't all that emission stuff POST-combustion?
Plug fouling, I thought was PRE-combustion?

I too reckon that modern cars have way more efficient fuel combustion technology designed into them. If I pull the plugs on my "modern" Maxima they're as white as Casper.
The 22 year old Porsche - light tan colour.

Still, that could be down to many other factors too - namely ageing.

[stlrj]

Sean,

Isn't all that emission stuff POST-combustion?

All that emission stuff, 02 sensor in closed loop, is in both post combustion and pre combustion at the same time.

Here in the US all we can burn is unleaded which leaves nothing to deposit on our spark plug tips. In the good old days when leaded gas was available and engines ran much richer, reading spark plugs had some meaning.

Cheers,

Joe

[Sean Hamilton]

Originally posted by stlrj
90 Bonneville

Ahh, a man after my own heart!

.........when leaded gas was available and engines ran much richer, reading spark plugs had some meaning.

And here, where we use that ghastly LRP (Lead Replacement Fuel) for our older classics, the deposited orange crap all over them makes reading a plug anybody's guess.
Bring on the Hydrogen fuel cell.