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Missfire at Light throttle , not sure which direction to go.

Canadian1968

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I had this problem last year , and a new set of plugs seemed to clear it up ?

This year its back again. It's a misfire at very light throttle , or as I roll into power. The harder I accell the less it is. I can watch my wideband, it show up on the AF gauge as lean spikes , and you can feel the power hit and miss as I try to accell.

I got home from work today left the car running got out to check things out. I did notice the fuel filter was almost empty , I could barely see fuel coming into it.

This is a brand new filter I just put on the night before. When I started it up last night , filter filled up no prob.

My next thought was vapor lock, I've never really had a problem with it though. Also I tured the car off and was able to fire it right back up, no problem. So not sure about that .

I also pulled the fuel pump pushrod out to check it , all good at 3.22"

I'm not sure what direction to go with next trouble shooting. Could be a bad fuel pump? Some carb tuning ? Something ignition related . I just don't know which way to go.

The only change over last year, was I did pull the heads and did a port job on them, also a new voltage regulator. New set of plugs when the heads were put back on. That's about it .
 
I had this problem last year , and a new set of plugs seemed to clear it up ?

This year its back again. It's a misfire at very light throttle , or as I roll into power. The harder I accell the less it is. I can watch my wideband, it show up on the AF gauge as lean spikes , and you can feel the power hit and miss as I try to accell.

I got home from work today left the car running got out to check things out. I did notice the fuel filter was almost empty , I could barely see fuel coming into it.

This is a brand new filter I just put on the night before. When I started it up last night , filter filled up no prob.

My next thought was vapor lock, I've never really had a problem with it though. Also I tured the car off and was able to fire it right back up, no problem. So not sure about that .

I also pulled the fuel pump pushrod out to check it , all good at 3.22"

I'm not sure what direction to go with next trouble shooting. Could be a bad fuel pump? Some carb tuning ? Something ignition related . I just don't know which way to go.

The only change over last year, was I did pull the heads and did a port job on them, also a new voltage regulator. New set of plugs when the heads were put back on. That's about it .
What is the fuel pressure? Are you running a vacuum advance? If so cap it off and see how it runs.
 
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