Question about 1990 Pontiac Grand Am
Not much information, but from what it sounds your catalytic converter may be restricted or plugged. Temporarily unscrew a O2 sensor and install a pressure gauge 1-10psi. More than 3 psi when you rev the engine means excessive exhaust back pressure and possible converter plugged. I used an old Ford 18mm sparkplug. Broke the porcelain out of it and brazed a 1/8 brake line into the metal sparkplug. Screwed it into the O2 sensor hole (same size and thread pitch). Hooked up an old fuel pump pressure test gauge. Started the engine and momentairly revved the engine using full throttle. Gauge shot up to 10 psi. Catalytic converter was plugged.
Posted on Oct 18, 2013
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Posted on Jan 02, 2017
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