I have an 87 YJ I recently purchased. It has a 258ci in it and a NON OEM carb. Before I tell you which carb (to keep info from being skewed by opinion) I will discribe the problem. I have the OEM Motorcraft ignition system installed.
First question, Does the feedback carb system affect or ajust the ign at any point? I have worked on several types of feedback systems and none affected the ign.

When idling the engine will randomly miss and sometimes stall as a result. The missing also will at times miss at hwy speeds. On my way back from a ride while cruising on flat road, even throttle, dry conditions, it will have a hard random miss. Once, at the above conditions, it cut out while in 4th gear (BA5 4spd) for about 2 seconds, then restarted (still in gear), it bogged heavily as if there was a complete loss of ign.
I have replaced while this condition has continued, plugs, wires, cap, rotor and a new OEM coil. No I was not throwing parts at the problem as all these components needed replacement badly.
I am also getting really bad valve ping when easing into the throttle say while cruising in traffic, 3rd gear 2K rpms or 4th gear below 2500rpms. My timing is set at 6*BTDC, but the ping will occur as low as 3*BTDC. I am not a fan of the Motorcraft ign modules as they like to leak off their dielectric and cause sypmtoms similar to mine.

My vaccume advance is working, but I hate the fact that the OEM distributor leaves the vaccume advance arm open to debris and water.
Second question, has anyone upgraded the distributor to something a little more waterproof?
BTW I did a search and spent some time researching, and I learned that if anyone brings up GM HEI....don't say I didn't warn you. <img src="/forums/images/graemlins/pfft.gif" alt="" />
Basically, I am thinking about replacing the ign module, I know some of the parts chain stores have testers for them but the kids that work there usually are not bright enough to hook them up much less read the results.
Oh yea, 500CFM Edelbrock performer on an Offenhauser intake.
<img src="/forums/images/graemlins/pfft.gif" alt="" /> <img src="/forums/images/graemlins/pfft.gif" alt="" /> <img src="/forums/images/graemlins/pfft.gif" alt="" /> <img src="/forums/images/graemlins/pfft.gif" alt="" />

As cheap as the ignition modules are I would probably buy a new one (or borrow one from Shreck!) and try it. I would also do the N****r bypass if it hasn't been done. Then I would get rid of that Carb and manifold! But that's just me. <img src="/forums/images/graemlins/lol.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/notooth.gif" alt="" />

Just a thought, but have you checked the wires supplying the coil with juice? I had a Ford P-up once that did the same thing, and the problem ended up being where the wire went into the eye connector. There were only a few strands of wire left connected. I replaced the eye connector and it was fine. Make sure you check both ends of the wires. Another thing you can check is on those same wires, make sure they have not touched or rubbed against anything hot. If the insulation has melted away in a spot and the conductors are intermitently touching a ground, that could cause this to.

Good luck and i hope this helps <img src="/forums/images/graemlins/smile.gif" alt="" />

Wylie valve clatter is caused by LEAN mixture or advanced timing... period!
So you have replaced both systems.. lets talk about LEAN first. That carb is a bit too large and so it should be able to get TOO RICH quite easily. If it has an idle adjust screw for each barrel screw both of em in to STOP while counting the turns and 1/8 turns.. I would start with them about 2 turns out.. If this makes the idle advance to more rpm then I would turn the idle stop back to a good 700 or so idle..
Now to the OEM spark system. In good health this is a fine spark system and should work well. HOWEVER after changing the carb you MUST do the nutter bypass! Period! If not done the computer will "feel" of the exhaust and retard the timing.. It'll never run right till the nutter is done.
Maybe I would right away do a leak down test to see if one of the intake valves is leaking too much. A leaky valve causes randon missfire.
All of that said I am confused by the complete cutoff of the engine at times.. When it comes back on does it pop and crackle? If so it would be a spark issue.. When the spark does resume it ignites unburnt fuel in the system causing backfire.. If NOT then I would look to a fuel problem.. FILTER? Pull the filter and blow through it.. If it is not real easy THERE is the problem.. You may have a simple problem such as a cracked fuel suction hose.. Your pump is sucking AIR and not enough gasoline is coming with the air.. Also do the propane test of the new manifold gasket..But I ramble.. Check these out and get back to us.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

OK for starters, I have heard of the N****r bypass in searches but never reference to what it entails.
Second the intake gasket is sound as is the base gasket(been checked replaced and rechecked) I will get a new module seeing that everyone that I have know that used this motorcraft module type, carried a spare for the leakout issue. So even if this does not help, I will then have a spare. I was leaning in that direction anyway. Repeatedly I have considered replacing the carb for being too much, I hesitate because the 4.0L is coming soon but is not at the top of the list. So I just want to make this one work until I do, so the $$ is not wasted on an interm upgrade. According to Edelbrock specs this carb, though overrated, should still operate on 258 cubic inches. The min is 239CI if I remember correctly from the spec sheet. The engine does not smoke (black or blue) which did make me wonder about a possible lean conditon, on decel you will get high from the fumes of unburnt fuel but still does not smoke.

The coil primary wires have that slide on connector on the "t" type primary posts and I have repeatedly checked them, but still question them.

The O2 sensor is not plugged up and is there only to plug the hole at this point. But if the feedback module this old still has a default setting if the O2 signal is missing. Though I thought that the Feedback was for fuel trim only, obviously not in this case if the N****r is required. Heck I don't even know if this thing still has the feedback module in it. Where would it be, it can't hide too many places that I have not seen.

No pop and crackle, just a jerk from the restart and heavy unburnt fuel odor from the exaust. The misses are a sharp thump (ign usually) not a bog out (like fuel). The filter probably has less than 500mi on it, but the return line setup off of the three ported filter is still hooked up. One inlet and two outlets, one centerline and one off to the side. I will check the actual fuel pressure this evening. I wonder if slack in the timing chain would give such a symptom. I have pulled the plugs for inspection and they look perfect, really light tan coloring, not washed or rich or shiny like a lean condition would look. <img src="/forums/images/graemlins/shiner.gif" alt="" /> <img src="/forums/images/graemlins/shiner.gif" alt="" />
All the typical indicators say this is not happening.

If I bring it down to 700rpm idle it will stall for sure, 900+/-rpms is as low as I can go to keep it drivable right now.

Check out this link.
ignition bypass
Scroll down a bit when you get there. Don't forget to read the disclaimer!<img src="/forums/images/graemlins/patriot.gif" alt="" />

With that carb and intake on there, there's a at least a 50/50 chance it's been done. <img src="/forums/images/graemlins/cheers.gif" alt="" />

I will drive it to work in the morn and start tinkering. Considering the jack legged crap I have had to reverse on this thing, I highly doubt anyone that worked on this thing before me had any type of concern of it running good. I'll report any improvements. Thanks for the leads guys.

Shrek also has an intake and I will be destroying my Heep soon so there is another intake and carb... We also have several modules available for testing purposes...

As far as I can see the N****r bypass has not been done. So I will strat with that this afternoon and go from there.

Sent ya some mail..
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />