New plugs,wires, cap,rotor. Back fires Thur carb if got on hard. Back fires Thur carb with air conditioner on more than when off.
Runs great than park it for 15 or 20 minutes. Restart it and runs like it is running on 3 cylinders.
Also has a new brain or computer. Vacuum line are all new.
Help driving me crazy

 

First ;
Did the vehicle have this problem before you replaced all the parts?
If it did, that's one thing.
If the problem showed up after replacing the parts, then the next question is did you replace the plug wires one at a time or some other way?
If you chose the other way, a whole new set of conditions arise.
The plug wires need to start in the correct place and follow a definite sequence (Firing order and direction) on the dist cap. Need to know these things in order to offer a possible cause and solution.

 

It started prior to changing parts. Plug wires were replaced one at a time. Trying to keep the same route as the old one. I don,t know how to detect a crossfire situation.

 

If you suspect a crossfire condition ,for your particular vehicle engine , just make sure the plug wires for cyls #5 & 6 do not run next to one another. (Those are the two cyls on the driver's side front of the engine). If possible keep them separated as far as you can.If that does not get rid of the backfire problem, there could be other causes among which could be possible timing problem, timing too far advanced, and carburetor accelerator pump problem possibly stroke too short or diaphram problem. All these things should be checked to eliminate those possible causes.