Under load missfire
 

I have a 1985 22re It was a new crate motor about 8000 miles ago. I left it set for a trip 5 days, I cam back and I have a under load miss fire bucks and and jerks for until it gets over 4 grand they it runs fine. I put in Zmax to clean the injectors and now it starts hard and realy lost power but after it gets over 4 grant it runs OK.

Well it has gotten worse I barely got home to night. I do not think the Zmax has anything to do with it for sure. It is little a hard starting until it gets warm. It seamed like if I had the lights off it made a difference and ran a little better. It is getting worse as time goes by. I am thinking it may be a bad fuel filter/ fuel pump (It was replaced 8000 mi. ago) or a bad distributor module (It was never replaced) .

The distributor cap and rotor are about 8000 miles old , I thought it could be that too the contacts do not look that great. but I do not think they are that used.

I had a friend that help me with problems like this but, he died. just looking for some help figuring this out.

Well, I think it is electrical, I started the motor this morning and it idled fine it had power until it warmed up a little as I was driving the 4Runner up in to the driveway. Correct me if I am wrong electrical will be intermittent and fuel problems are consistence.

I would look more at your ignition components at this point. Since you stated that it started missing under a load, usually that is when the ignition is at its peak power., what i usually do is get a spray bottle with water and spray the plug wires down with the engine running to see if it is leaking spark. If there is spark leaks in the wires the water will cause it to ground out and you will be able to see and hear the poppong noise. also check the coil and wire. if you dont find it there pull the cap of and check for moisture or burnt spots in the cap and rotor. Hope this helps. it could also be fuel related to but that would be another topic, i would check the ignition first cause its the easiest.

check your plugs and see what they look like. It will tell you some info like is it running lean/rich or they're just fouled.

Check your spark plugs and connections. When my truck misfired under load it was the spark plugs both times. The first time they were just old, the second time it was a faulty spark plug. Did the same thing as your truck, misfired under load but was okay after a certain higher rpm.

Cheers