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P0172 OBD2 Diagnostic for 1999 Chevrolet 5.7L Engine: Carbon Fouled Spark Plugs and Injector/Intake Valve Issues

Model: 99 chevy 5.7 Fault Code: P0172 Posted: 2010-09-16 21:31

I'm experiencing a P0172 code on my 1999 Chevrolet 5.7L V8 engine. The issue appears to be related to cylinders 5 and 7, which have carbon-fouled spark plugs. I suspect either leaking fuel injectors or intake valve problems as potential causes. Since the engine is running with a lean condition (as indicated by P0172), I'm trying to determine whether this is due to injector leakage, worn piston rings, or other internal combustion issues. I've already inspected the spark plugs and noticed that cylinders 2, 4, 6, and 8 have normal appearance, but cylinders 5 and 7 show significant carbon buildup indicating poor combustion efficiency.

Related fault codes
P0172
Comments (2)
Anonymous 2010-09-19 18:31

Try using Seafoam for a complete fuel system induction cleaning. It helps remove carbon deposits from intake manifolds and combustion chambers. You can find detailed video tutorials on YouTube by searching 'Seafoam induction cleaning'. This may improve engine performance and reduce the P0172 code if the issue is due to carbon buildup.

Anonymous 2010-09-20 20:43

well i wish seaform would fix it but i don,t think it will, If i had a scanner to look at my fuel trims i would know more about it but what i do know is 2-4-6-8-1-3 plugs look good but 5-7 are fould out so either thier is an injector issue or worn rings but i never did a comp test i was just hopeing someone had come across this prob before