Fouling out plugs
- Thread starter 92typhoon
- Start date
Re: Fouling out plugs
Valve seals are loose or worn out.
Solution:
Step up to a hotter plug or fix the seals. The original GM valve seals are guaranteed to start leaking after the 30,000 mile warranty expires.
It is usually the intake valves on cylinder #3 and #4 that start leaking first because of the stinking vacuum EGR port on the TBI and CPI engines. GM eliminated the vacuum EGR in the 1996 - 2002 Vortec SCPI engines and started using a linear/digital EGR valve.
I use Denso PTF20TT platinum spark plugs. If you have fouling issues try Denso PTF19TT which are a step hotter. Those are Denso fine wire platinum and are pre-gapped at .040". The Denso plugs come with a plastic sleeve so the gap is protected until they are put into service. Denso are obviously better quality than AC Delco Rapidfire #1 spark plugs that everyone is so crazy about. GM has spun off AC Delco Spark Plug Division and they are now made by the lowest bidder. .
NGK makes expensive AC Delco Professional spark plugs, at least that was the last I heard. Since the GM bankruptcy, that has probably changed and they too may be made by the lowest bidder.
Valve seals are loose or worn out.
Solution:
Step up to a hotter plug or fix the seals. The original GM valve seals are guaranteed to start leaking after the 30,000 mile warranty expires.
It is usually the intake valves on cylinder #3 and #4 that start leaking first because of the stinking vacuum EGR port on the TBI and CPI engines. GM eliminated the vacuum EGR in the 1996 - 2002 Vortec SCPI engines and started using a linear/digital EGR valve.
I use Denso PTF20TT platinum spark plugs. If you have fouling issues try Denso PTF19TT which are a step hotter. Those are Denso fine wire platinum and are pre-gapped at .040". The Denso plugs come with a plastic sleeve so the gap is protected until they are put into service. Denso are obviously better quality than AC Delco Rapidfire #1 spark plugs that everyone is so crazy about. GM has spun off AC Delco Spark Plug Division and they are now made by the lowest bidder. .
NGK makes expensive AC Delco Professional spark plugs, at least that was the last I heard. Since the GM bankruptcy, that has probably changed and they too may be made by the lowest bidder.
Last edited:
Throws
Active member
Re: Fouling out plugs
This is my next project... I can't wait to do it. On one plug, the plug/electrode were bridged with all the oil residue.
-P
This is my next project... I can't wait to do it. On one plug, the plug/electrode were bridged with all the oil residue.
-P
sytyguy
Moderated User
Re: Fouling out plugs
If not, you may have a very weak coil or overly tight-gapped plugs.
If it's fuel fouling try inspecting the fuel pressure regulator. Crank the engine and let it idle for a few minutes. Turn off the engine and pull the vacuum line from the top of the regulator (to the left of the EGR valve when facing engine). Do you see fuel dripping out? Does the line smell strongly of fuel? If so, you have a busted diaphragm in the regulator.....replace it.
If not, you may have a very weak coil or overly tight-gapped plugs.