Let me start by saying i have been reading alot in this forum and this place seems pretty cool . so that being said now down to the dirty. i have a 89 yj with a carter bbd it is the 4.2 it has a very noticeable miss at all rpm i am aware of the nutter bypass but as i live no. cal i am unable to have this done "smog reasons" i am also not sure that it would solve this problem i have tested the coil it is fine no vacuum leaks and the up and down stream air tubes are in working order. i would like to test the ignition control mod con any one post a wiring diagram for this it would help alot, or if someone has any idea where else i should check please help thank you.
Pull off the spark plug wires one at a time and see if any one of them doesn't change the way it runs. Obviously, shut the engine off before you touch the wires. The one that doesn't change the way the engine runs is bad, either compression or bad spark plug or wire or something.
made no difference on any of the plug wires. also dancytron i looked at the link and my jeep is in a rich condition, the stepper motor works as does the o2 sensor. also on the link and in the forum it says to drill out the two tubes that go to the ventures, i was watching them and one drips one does not, so pulled them. they both were really clean i am going to rebuild the carb and drill them out. also it has ngk plugs that were new, but were gaped at .40 thou not .35 does anyone think that this would make it misfire. the plugs look really sooty, i think i am goin to chang to champion as this is the plug it came with from factory. any opinions would be greatly appreciated. thank you for your time
Last edited by Snicklfritz; 11-01-2011 at 07:06 PM..
try spraying some carb choke cleaner around your intake focusing on the base of your carb. Go around it and listen for it to die almost choke out. I have just dealt with that thinking it was a miss fire when I was pulling from a bad carb base plate gasket.
These engines like the plain Autolite plugs, stay away from the fancy sparkplugs.
Gap to .035
Add a dedicated ground to your ignition system. Easiest way is to tap into the black wire coming out of the distributor. This wire is the only ground for both your ignition module and the coil. It normally grounds via a screw in the distributor, then to the dizzy hold down clamp, then the block. Not a good ground path for such a critical electronic component.
418 miles on 19 gallons of gas. Can't beat the BBD !
If your 4.2L has had the Team Rush mod (the Ford cap/rotor) done to it then .040 would be the gap to have. If you are still running the stock dizzy cap/rotor then .035, like Old4X said. But if you are still running the stock cap/rotor, do the Team Rush upgrade with the coil. Makes a difference.
to all who responded let me start by saying it has not had anything done, bone stock original, i have sprayed down the base gasket and the vacuum lines to no avail. i am going to rebuild carb and put new plugs in it then i will add a ground from distributor to block. will let you know what out come is. i did not use d reader to see the function of stepper, i made a lean condition and then a rich condition, and watched it move. you can see it, it is in middle sometimes, but for the most of the time it is all the way forward.