1990 Chevy Lumina misfire

EZALAMO711

MEMBER
1990 CHEVROLET LUMINA
6 CYL
FWD
AUTOMATIC
86,000 MILES

Can a clogged catalytic convertor make an engine misfire? Started misfiring after driving 5-6 miles but now it starts right up and misfires, runs poor, just changed plugs and wires today. 6 months ago changed a bad injector fuel filter ignition module. I think its the cat convertor

Monday, November 30th, 2009 AT 12:32 AM

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

To rule out the Cat do a backpressure test on the exhaust system or get a gas analysis test

Oxygen sensor
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires

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Monday, November 30th, 2009 AT 12:53 AM