Misfiring while cruising

[jalexquijano]

I just noticed 3 and 4 and the car was left running with the Hood open in straight sunlight for only 10 to 15 mins. We already replaced cap and rotor, check cylinder compression. What else now?

[Mark Maras]

 Check the other plugs to see if they're all black or if the problem is isolated to #3 and #4. Verify that the choke cables are adjusted properly and that the cables aren't pulling the nozzles down when the choke knob is all the way forward.

[jalexquijano]

1 hour ago, Mark Maras said:

 First things first. Were all the plugs black or just #3 and #4.

I really want to move forward with the solution to this issue before i send the car to the paint shop and buy some konig rewind wheels.

[jalexquijano]

2 minutes ago, Mark Maras said:

 Check the other plugs to see if they're all black or if the problem is isolated to #3 and #4. Verify that the choke cables are adjusted properly and that the cables aren't pulling the nozzles down when the choke knob is all the way forward.

i already cleaned both plugs with a brass brush and carb cleaner. I will need to leave it at idle again to see what happens.

[rcb280z]

Mark has suggested several times now to check all plugs, have you done so yet? Are the rest of the plugs like 3 and 4, fouled?

[siteunseen]

I'm grasping at straws here but have you checked the gap on those plugs, IF they are the only ones that are fouled?

 

Edited September 24, 2018 by siteunseen

[Mark Maras]

I'd really like to know if all the plugs are black. If only #3 and #4 are black it narrows down the possibilities from a wide range of causes to the cap, rotor, wires and wire connections. 

[siteunseen]

Me too.  Those are the two that separate the dual carbs so it doesn't seem likely it's the cam or the carbs.  Could be as simple as the wires aren't connected good and tight.  My NGK wires make a nice SNAP noise when I put them back on the plugs.  The tip on our plugs can become loose to.  Tighten with pliers.

[Mark Maras]

25 minutes ago, siteunseen said:

Me too.  Those are the two that separate the dual carbs so it doesn't seem likely it's the cam or the carbs.  Could be as simple as the wires aren't connected good and tight.  My NGK wires make a nice SNAP noise when I put them back on the plugs.  The tip on our plugs can become loose to.  Tighten with pliers.

 I still think that the original problem with #4 was a poor wire connection at one end or the other. I think we ruled out other possibilities. That said, @jalexquijano have you explored the possibility that Previously #4 had a bad connection and now #3 and #4 have the same problem? Oh yeah, I still want to know if all the plugs were black.

[jalexquijano]

Okay. We know that the compression is good and the cap and rotor are also new. So what remains? Should i clean all the 6 plugs and cranked the car leaving it to idle for 20 mins to see if those plug foul to black?

[rcb280z]

Ok lets try this a different way. Go out to your car and pull all 6 plugs (now) and take a pic of them (now) and then load that/those pics so we can see all six of them (now).

[Zed Head]

On 9/23/2018 at 1:40 PM, jalexquijano said:

Today's update:

Drove my car on light sunday traffic. Parked and let the engine run at idle for 10 mins with the hood opened. Step on the car and started accelerating. Car misfired a couple of times so when i got home i pulled plugs 3 and 4 and found them black. Is this normal? This is what happens when the car is sitting on traffic at idle.

This is the old fuel percolation problem from way back, I think.  Never got solved.

How hot was it on Sunday?