1990 RENIX misfire backfire on acceleration

Ok I have a 1990 jeep cherokee with the 4.0, idles ok it has a little bit of fluctuation but not bad when I try to accelerate it'll go fine until about 10mph and then you can feel it bog down and loose power it misfires and backfires out the exhaust, and the only way to really go smoothly is if I pretty much floor it until I get up to my desired speed and I can get it to cruise pretty well but if I take my foot off the pedal just a little bit it looses power and backfires and misfire like crazy sounds like somebody through some firecrackers in the tailpipe

I have 3 inch lift, it's on 33s, strait pipe from the cat back, duals from the cat, no muffler, I have 4 lights on the roof and 2 in the grill, my headlights are dim and the harness connector behind the headlight is pretty corroded and crappy, my bolts drop almost t

The electric fan will not turn, on previous owner ran a jumper on the temp sender in the rad so it runs all the time, my temp gauge never reads above 180 or so,

My Volt gauge drops low if I turn the heater fans on or the roof lights and grill lights on



I've replaced, plugs, wires, cap, rotor, tps, fuel regulator, crank sensor, o2 sensor,

My exhaust manifold is cracked right where the weld is about an inch above the o2 sensor, I already have a new ex manifold and gaskets

The old plugs looked really sooty with a tanish Brown color underneath the soot, Idk just thought I'd mention that


I'm about to order a fuel pump and put the new exhaust manifold on

I'm getting tired of this thing it needs fixed

ANY IDEAS???

I've thought about timing, and reindexing the dizzy, if I cut the mounting tab off wouldn't the distributor move around with that cut off?

I forgot I also replaced the ignition coil also


Could air in the cooling system on a renix make it run like this?

Also leaned grounds and upgraded thicker wires, dipstick, rear of the head and the one off the battery to the front support

I can get it to misfire and backfire while it's parked it does it in the same spot it seems like maybe 25% throttle, and it'll sound like a machine gun out the tailpipe.

This is crazy it runs super smooth unless I get on the throttle wtf??

Check valve in fuel tank? Can that cause it to backfire and mis?

It's an automatic by the way

Have you checked your fuel pressure? Both at idle and with throttle?

Have you done any of the Renix diagnostics?

http://naxja.org/forum/showthread.php?t=1115935

Could be a worn out or crap rebuilt dizzy.

My money would be on a rotted fuel pump hose. Ethanol gas is hard on the 20+ year old rubber fuel lines. The pump will flow the correct PSI at idle, but as soon as you put any load on the engine then the hose will bleed fuel internally back into the tank, causing the loss of power and backfiring that the OP described.

Long story short, check your fuel pressure at idle and throughout the throttle range.

I vote for indexing the distributor.

I was definitely thinking the line in the fuel pump was rotted, I'm pulling that thing tomorrow and checking it.

I've also thought about indexing the distributor or replacing it all together, but I'm gonna check the fuel line in the pump first and go from there.

I'm doin the ball joints tomorrow cause there gone at least the upper on the driver side is, anyway I'll be all over it tomorrow should be warm out

Ok so I pulled the fuel pump the rubber line was still holding although it was a little mushy, I'm gonna replace it the line anyways tomorrow, and there was no sock on the fuel pump either.

I don't think the pump is the problem...

When I adjust my TPS I have to adjust it all the way out to its farthest setting to get it in spec, almost like the butt of the TPS is pointing up, I don't think this is adjusting right even though I've done it 50 times and it still ends up in the same spot. Old it could be right I guess.

WTH is wrong with this thing???

I was thinking distributor also. I don't think you should cut off the mounting point. If its installed correctly, the bolt will pass through he cut out for it. On later 4.0's, distributors do not adjust timing like on other vehicles with mechanical/ vacuum advance. The distributor delivers spark and contains a cam position sensor which helps control the fuel injectors. RENIX may be the same.

I forgot my fuel sending unit is broken at the metal tube on the top we're there fuel comes out of the tank, the weld is broken at the flat round part and the pump basically boggles around in my tank, I'm not sure if fixing this will fix my problem but it is letting air in and possible moisture, looks like I'll be ordering it up soon

Wiggles not boggles

Not sure if this applies to your renix, but my 96's fuel tank baffle came undone(high-g auto-x) so the rubber-locating foot of the fuel pump moved with it and ripped the tube support from the plate. The fuel pump ground is attached to the external plate then carried by the tube internally.

Did that cause your jeep to have sputtering or backfiring issues

I lost the pump completely. You might have a compromised ground.

Ok thanks for your info I'm changing that sucker out

Just went through this same issue on my brothers rig. Spent tons of time trying to trouble shoot it.. in the end it was a clogged cat converter. Just unbolt the cat at the flange by the cross member and let it hang there and then fire it up. If it now runs awesome and you can rev it without the backfire and sputtering you were getting before then that's your problem.

I'll definitely try unbolting the cat and see how it goes, I should probably go out there now and soak the bolts with some pb blaster. I can't order any parts until Friday so I'll toss the old pump back in for now