83 4.9 van

Hello, I have a 83 e100 conversion with a 4.9 staight 6. This is the story from start to now, I bought this van 4 only $300 but it ran good but it had a little misfire but nothing i would worry about. so about a week ago i was driving and it started to mis bad so i changed the plugs and wires and it got even worse,so i changed the cap,rotor,coil and it got even worse.i had the module checked and it was good. Soooooo any help would greatly appreiated.

Misfire through all the RPM ranges? Idle OK?

Idle not to bad but some misfire(very little) but under load....bad misfire and all rpm ranges. Now I am getting a new ignition module today and I can only hope that this is the problem even though it check out ok.........But your input would be great

 i have the same van. 82 e100 4.9 inline ..... your problems seem similar to the problems i had when i first bought my van for 3 hun too.. and i replaced all the plugs wires, fuel filter, and so on. had the carb rebuilt now she runs like a champ.

1. Thanks for the input, i did that to syill nothing. i just bought the ignition module just to be sure they didnt check the old one right.but no change,now it seems to do 1 spark when i turn the key on and 1 spark when i turn the key off,but none while the van is being cranked over. I dont think so but can the problem lye in the ignition switch not the tumbler but the switch it self.
   
2. N E help is great.

are you sure your timing isnt off?

how many miles is on your van???

this might not be in effect but when i bought my van, it had been sitting for 4 years in a field...... could your cat or your muffler be clogged???

just my 2 cents

Could also be a vacuum leak.  Worked on the same type running issue on a 83 F-150 last year.  Easiest way to check for that is this.
 
1. Remove the air cleaner
2. Start the engine
3. Cup your hands over the carb and slowly start blocking off the air flow
4. Continue until you choke the engine to a stall or the engine idle smooths out
 
If the idle smooths out, then you have a vacuum leak.  The RPMs will sometimes increase as the idle gets cranked up to compensate for the leak.  Spray carb cleaner around the carb base to check for leaks.  The F-150 I worked on has a bad base gasket on the carb.

I thank you guys for your input thats y i came here, i quess first,i ckecked the timing 5 times thinking maybe i was missing something(hehe) but it is good. As for the carb workchecked with spray also and for vac leaks, everything is good. ive been working on my own cars,trucks,bikes everything for about 25 + years and this is the first time i can not figure it out or my friends at that. Q: could it be that ignition switch it self .I get 1 spark when i turn the ignition on and 1 when i turn the ignition off but none to the coil while cranking. Again thanks for the help.

Have you checked for constant voltage to the coil while cranking?  How about fuel filter and fuel pump?

i did check the fuel pump and filter and they are good, no it does not get constant voltage to the coil(i dont believe it does anyway) it does not spark while it is cranking.i changed the ignition module for no reason it seems because it didnt change anything.Its definitly not the carb or a gas reason right now its just not getting constant poer to the coil.e chacked everything that i could think off so all the help from you guys is really great.sooooooooo again thatnk you

Not trying to be a smart alleck but you do know there are two different timing marks. 

Yes.no offence taken