I am having a problem with a miss. I have change the cap, rotor button, and coil to MSD, put a control module from Jeg's in it, put some 8.8mm accel 300+ wires on it and I still have a miss. The only thing there is left is Plugs that are only 6 months old or a blow head gasket. The timing is set at 12 degrees advanced. I hope and doubt that it is a head gasket because I ran It down the track one more time After it started to act up. What do you fellas think it could be.

 

Is the miss somehting you can feel? Or is it something you hear?
If you "hear" the miss you may just have a leaking header gasket (if you have headers).

~M~

 

no you can see it, hear it, feel it, and you can even watch the tach vary from 500rpm to 600 and it isn't consistant
yeah have slp headers it can asure you that is not it.

 

tried new plugs? might have one fouled or weak and can't spark well.

~M~

 

You may have a bad injector that's not firing. First you need to
determine if you have a miss. With the car, running pull the
number one plug wire off the cap. If the rpm's drop, that cylinder
is ok. Put that one back on and pull number eight wire off the cap.
If the rpm's drop, that cylinder is ok. Continue around the cap
pulling the wires until you get to one that does not drop the rpm's
and that will be the one with the problem. If all of them cause a
drop in rpm's you do not have a miss.

If you find a cylinder that does have a miss the first thing to do
is put a different spark plug in it and check it again. If you don't
have a spare plug in your tool box just trade places with another
plug in you engine. Fire it back up and pull the wire on the bad
cylinder again and also on the cylinder you traded plugs with.
If the miss moved to the other cylinder you traded with then you
have a bad plug. If the miss stayed in the same cylinder, at least
you ruled out the spark plugs.

If it is not the spark plug causing the miss you need to Ohm the
injectors. Check them cold first before the engine has been run
that day then check them again after you let the engine reach
operating temp. You want readings above 12.5 Ohms. They may
read higher when cold and drop some when hot. If any are below
12, replace them. The one on the bad cylinder may even be down
to like 2 or 3 Ohms and not be firing at all.

If the injectors check ok, then you need to run a compression test
on the bad cylinder. If it is below like 120 or so you may have a
burned valve or other problem. If the compression is good try
swaping the injector on the bad cylinder with another one and
see if that cures it. An injector can Ohm good but be stuck shut
or clogged

Those are some basic checks you can do to get started.