Mechanics

MISFIRING

1997 Pontiac Grand Am

1997 Pontiac Grand Am 4 cyl 173000 miles

i have replaced the cam sensor, crank sensor, coil, timing chain plugs, tested fuel injectors, changed the plug boots and it still misfires 1 and 3 everything ive done it still misfires 1 and3
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Webangel
August 6, 2009.



Hello, a misfire can be caused by just about anything. Did you visually check for spark at the plugs? Fuel pressure ok, use a gage?

JDL
Aug 6, 2009.
Yesi have visually checked spark have it 1 and 3 still misfieing

Tiny
Webangel
Aug 6, 2009.
What was the fuel pressure spec? Are the injectors pulsing?

JDL
Aug 6, 2009.
The fuel pressure was good and the injectors are pulsating could the lobes be worn or valves burnt how do I find out

Tiny
Webangel
Aug 6, 2009.
You can't check proper fuel pressure without using a gage. Do a compression test on the cylinders.

JDL
Aug 7, 2009.
Compressioncheck is 180 lbs we did a leakage test and 1 and 3 misfires 2 and 4 has a 25% leakage

Tiny
Webangel
Aug 7, 2009.
Maybe I misunderstood your post. To do a cylinder leak down test, the engine isn't running. The cylinder your checking, you bring the piston up to tdc compression stroke, pump in air through the spark plug hole, shut the air valve off, watch for a leak-down. Right now, I'm not sure why the misfire.

JDL
Aug 9, 2009.