Misfire, can't find problem and have tried everything. Please Help

My Maverick has a 89 5.0. Cylinder 4 is dead (rear cylinder passenger side). Not firing and blowing lots of gas out of the exhaust. It has a street avenger carb, weiand intake, MSD 6al, msd coil, msd wires, msd cap and rotor and stock distributor. It has spark at the cylinder. I even swapped out the MSD box, cap and rotor, plug wires and got new plugs(same problem). Took off carb, cleaned and reinstalled(still same problem). Tried a friends edelbrock carb(same problem). Compression tested all cylinders and all are good. Checked valves and they are opening as they should. Looked in cylinder with camera and it still looks new. Roller rockers rock as they should. I am at a loss. I am thinking either the Distributor (even though it has spark possibly just not firing at the correct time), or could it be a intake manifold or head gasket leak. Any help would be greatly appreciated. I have been trying to figure this out since September. Thanks

 

Based on that info.. I'm guessing that the magnetic pickup is pooched and has a very weak signal to the coil. Just because it fires during cranking doesn't mean that it'll fire when the cylinder pressure goes up as it's running.

DS parts are easy and cheap to swap out and that's the first place I'd be heading from here.

 

I have pulled the plug wire with the it running and the spark jumps from the wire to the plug.

 

how do you know its cylinder #4 not firing?
what cam shaft are you using?
what firing order are you using?

 

Firing order is correct. Using the HO firing order. Turned off car last fall then started it the next day and had this problem. Cylinder 4 plug (rear cylinder on passenger side) is wet with gas and has no sign of ever firing (still looks brand new) and header pipe does not get hot while the others do. I do not know what cam exactly but it is pretty aggressive.

 

You missed the point. Cylinder pressure causes the spark requirement to go up exponentially. Pulling a plug and checking spark jump is not nearly the same as the environment the spark must contend with when installed. This is why ultra high compression and exotic fuels need so much spark energy to light things off.

So, aside from the plug being bad as Bryant already mentioned.. or you missed something during the troubleshooting process?.. you likely have bad ignition module.

 

you listed every thing possible. you must have missed something.
first thought is you have a bad spark plug.
you said you replaced them. then you say the plug is covered in gas. this will foul the plug. the question becomes why is cylinder 4 fouling the plug. is it just the one that was coated when you pulled the plugs?
i would check exhaust port temps. you can do this with a infrared temp gun or a squirt bottle of water. check each header tube or exhaust manifold port where it meets the head. this will clearly locate which cylinder or cylinders are not firing.

 

been there done that...

 

Since I have swapped the msd boxes out and it did not fix am I correct in thinking the next step is the distributor?

 

Sigh.. not giving up on you yet and still trying to help you here, bud.

It's like this. If you want to go through all the trouble to replace the whole kit and caboodle to say that you threw every ignition part known to man into the mix here?.. then yes.. spend the extra time and money to swap the hole disty out and call it done. Otherwise.. there's really only one electrical part in there that goes bad from a connectivity standpoint.. so, just swap out the pickup itself without much time, effort, and cash compared to the other troubleshooting procedure. That's about all I can say here. Good luck with it all.

 

I will try it today when I get home from work. Fingers crossed, Thank You

 

Good luck.. for your sake.. and sanity.. I really hope that's it. :Handshake

 

The module I got doesn't fit. I have a billet distributor coming next week. Have wanted to get one for awhile anyway. I will keep everyone posted. Thanks for the help.

 

i have seen new spark plugs that are bad.
i would try switching the plugs between cylinder 4 and any other cylinder and see what happens.

 

I too have got brand new plugs that were bad. I've tried 3 different plugs to no avail. I pulled the wire off the plug with it running and the spark didn't jump as far as the other wires and didn't snap as loudly as the others. I am hoping the new distributor will fix. Distributor is the only part of ignition that is old and it could be worn.