Need some help with rough running

I have a 94 with a 4.0 engine. The check engine light goes on and off. I replaced the wires and plugs. No change. It has a flat spot when I floor itand some time it misses. I check the new plugs after a few miles and the front left one was pure white. I tried injector cleaner as when I check the codes with my home tester it said the injector spray was narrow. If anybody has some idea that I could try. I don't mind replacing the injector but you have to take the whole top of the engine apart to get at it

check your oxygen sensor.

I had the same thing with lack of power, plugs and wires didn't help either, new distributor cap and rotor had it purring like it was new.

This is my second car so I been putting off working on it as The Aerostar is not the most fun to work on. I check the Oxygen sensor and it was fine. Some time when I start it runs fine tell I punch it down and then the miss stays. I well try replacing the cap and rotor as thats a lot easyer then replacing the injector. Thanks for the information

Don't forget to let us know what worked, I try the easy stuff first, mine was a 1990 3.0 V6. Jeff

I went to check it out and the 4.0 has no cap and rotor as it's a distributorless ignition. The wires plugs in the coil. The only code I can bring up is injector spray is narrow. I think everything points to the injector. I have tried cleaners and no luck and for what they want to shop clean them on the van I can get six rebuilt injectors. I guess I'm going have to take it apart.