My engine has a bad miss and it turns out the number 3 cylinder is dead. We can't figure out what the issue is. Did compression test, numbers were normal for the age of the engine and all with in 5% of each other. The dead cylinder was 2nd highest actually. We checked all the valve clearances, all in specs. Changed out all the plugs, new wires, new cap/rotor. The old plugs were all clean and light cream colored, black electordes, no deposits or such except for number 3. The porcelin on the plug was medium tan color and had about a .5mm v grove cut into the side of it. The thread area was a dark black color. We put new plugs in it and ran it for about an hour total and pulled the plugs again. Same ****. All clean except 3. It was starting to turn brown, no deformities yet. The engine doesn't smoke at all, and doesn't seam to loose any oil or antifreeze. The reason we know the cylinder isn't putting out any power is when it's running you can pull the spark plug boots one at a time and get drop in engine idle except with number 3. Absolutlely no change in engine perforance when that boot is pulled. Yes there is spark at the boot on all cylinders.

Anybody have any thoughts on what's wrong with number 3?

 

Check for both spark and fuel in #3 while the motor is running.

 

sounds like a fuel injector sticking, give it a light tap with a screwdriver (not the tip, the handle) and a hammer to see if that helps loosen it up, if it dosent move the injector to another cylinder and see if the problem follows it. id replace the plug or at least clean it before you try anything.

 

Thanks for the tip on the fuel injector, but this engine is carbed, which is what makes it so damn puzzling. IF the other 3 are getting fuel the bad cyl should be getting fuel also. I already know that there is spark there. I'm at a loss.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jerseydevil &raquo;</TD></TR><TR><TD CLASS="quote">Thanks for the tip on the fuel injector, but this engine is carbed, which is what makes it so damn puzzling. IF the other 3 are getting fuel the bad cyl should be getting fuel also. I already know that there is spark there. I'm at a loss.</TD></TR></TABLE>
wow interesting

any way you could get pictures of the spark plugs?

 

What kind of vehicle?, what kind of intake manifold?

 

It's an F2 mazda truck engine, stocker manifold. Currently setup to run on Liquid propane. I know it's not honda guys, but basic engine theory should apply.

I'll have to see on monday if the plugs are still around, they may have been tossed already.

 

Anybody have any ideas?