O2's and an ignition miss
12-15-2006, 07:25 AM
#1
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O2's and an ignition miss To me this seems like a stupid question but hey might as well go for it.
Can a bad upstream O2 cause a misfire that can be seen on a timing light?
It is on every wire it seems. Misses only with the engine at temp under load not at idle and not cold. I put the timing light on each wire and then throttle it around and the light pulse is not steady at all. The timing light shows the missing pulse. The miss is noticeable when it happens, especially maintaining speed behind grandma. Car bucks slightly.
Any takers on this one?
Car threw P0303 the other day. Plugs, wires are new about 6K. The miss just started up one day. Drivers cat replaced at 30K but not the O2.
2000SS, auto, 45K, Stock.
Can a bad upstream O2 cause a misfire that can be seen on a timing light?
It is on every wire it seems. Misses only with the engine at temp under load not at idle and not cold. I put the timing light on each wire and then throttle it around and the light pulse is not steady at all. The timing light shows the missing pulse. The miss is noticeable when it happens, especially maintaining speed behind grandma. Car bucks slightly.
Any takers on this one?
Car threw P0303 the other day. Plugs, wires are new about 6K. The miss just started up one day. Drivers cat replaced at 30K but not the O2.
2000SS, auto, 45K, Stock.
12-15-2006, 12:31 PM
#2
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P0303 is cylinder 3 misfire. You say it is showing a miss on all cylinders? Maybe you can switch the O2's from driver side and passenger side. Clear the code and see if the misfire moves to the other bank. The only way I can see it causing a misfire is if the engine was running crazy rich or crazy lean. Possibly a weak/dirty ground? Check the grounds for the coils and the O2's on the back of the head. Just some random places to start looking.
