Reading plugs, what's going on here?

[BLSTIC]

So my mate pulled these from his 95 Tahoe (factory 350 tbi) and it's a bit confusing. How is the ground electrode so clean when the rest of the plug is sooty? Is it being washed or something?

No real symptoms, just not running very cleanly when cold (when comparing to our more modern cars, so it might just be characteristics of the era) so he pulled the plugs to look

received_934415454100237.jpeg

received_2912575075660083.jpeg

[ClassAct]

The ground strap is ignition timing. The porcelain is the tune up. It’s certainly rich.

[1980RS]

TBI engines always ran fat, never cared for them.

[Geoff2]

Plugs too cold?

[BLSTIC]

The ground strap is ignition timing. The porcelain is the tune up. It’s certainly rich.

The car certainly has ignition timing... Would this indicate too much or too little advance?

[Walter R. Malik]

Terrible gasoline you get from the pump these days, I would suspect... along with to cold of a spark plug.

[maxracesoftware]

So my mate pulled these from his 95 Tahoe (factory 350 tbi) and it's a bit confusing. How is the ground electrode so clean when the rest of the plug is sooty? Is it being washed or something?

No real symptoms, just not running very cleanly when cold (when comparing to our more modern cars, so it might just be characteristics of the era) so he pulled the plugs to look


received_934415454100237.jpeg

received_2912575075660083.jpeg

looks like Plug Heat Range is close to being slightly too Hot , and Air/Fuel Ratio too Rich
for operating RPM/Load whenever these Pics were taken at !

I'd like to see Pics "after" Air/Fuel Ratio was correct for RPM , then look at Ground Strap for Heat Range,
Plug should be close to being too Hot .... as is in your Pics... Plug Heat Range appears just Hot enough to prevent fouling out from Rich Mixture.

[af2]

Plugs too cold?

Exactly!!!!!!!!!!!!!!!!!

[maxracesoftware]

Plugs too cold?

Exactly!!!!!!!!!!!!!!!!!

i disagree
what's the Ground Strap going to look like
when he gets the Air/Fuel Ratio correct for RPM/Load Range ,
its going to be even hotter looking than those Pics !
The Heat Range "wittness mark" is going to move even close to the Base-Ring !


i got a whole bunch of Pics like that thru the years, ( mostly on Low CompRatio Engines with Pump Gas )
and when you get the Air/Fuel Ratio correct for RPM/Load Range , the Plug's Heat Range is usually now too Hot or just enough .,
if it were "too cold" , the Ground Strap would also showup too cold ... and you would be looking at Pics that were mostly fouled out everywhere

[Amilcar]

So my mate pulled these from his 95 Tahoe (factory 350 tbi) and it's a bit confusing. How is the ground electrode so clean when the rest of the plug is sooty? Is it being washed or something?

No real symptoms, just not running very cleanly when cold (when comparing to our more modern cars, so it might just be characteristics of the era) so he pulled the plugs to look


received_934415454100237.jpeg

received_2912575075660083.jpeg

looks like Plug Heat Range is close to being slightly too Hot , and Air/Fuel Ratio too Rich
for operating RPM/Load whenever these Pics were taken at !

I'd like to see Pics "after" Air/Fuel Ratio was correct for RPM , then look at Ground Strap for Heat Range,
Plug should be close to being too Hot .... as is in your Pics... Plug Heat Range appears just Hot enough to prevent fouling out from Rich Mixture.

Larry, care to elaborate a little?
How does a colder/hotter spark plug,would manipulate more/less heat received on the ground strap, as it already belongs to the outer body of the spark plug?
To my understanding, colder/hotter plug, are relationship as how much heat, center electrode/porcelain can dissipate to the outer body of the spark plug and that includes the ground strap.
Thanks

[V12MECH]

OBD1 ECM , may have codes for failed O2 sensors or coolant temperature sensor driving injector pulse too long, what is data stream info with good scan tool? If plugs are correct type, a weak coil , defective fuel pressure regulator in TBI unit, ck. fuel pump pressure, map sensor ,( trouble code) , might be the problem, ground strap color and fuel quality are interesting, we work on these everyday, base thread ring may have carbon on it, but on a good runner , plugs are very clean.Post some more info when you fix it.

[Firedome8]

Verify proper heat range for your application, find a chassis dyno and check the timming and afr, scope out the ignition to eliminate bad coil etc.