Some of you may have been following the saga in another thread.

Recapping, my Z24i has been cutting out around 2500 rpms. It ran fine up to that rpm "limit". I'll spare you the parts I've replaced, time and money I've spent (you can read the other threads to see the history). Turns out the issue was with a buried splice connector in the main harness that feeds power to the 2 injectors. For some unimaginable reason, Nissan engineers spliced the 2 power wires (one for each injector) down to one wire, then about 8 inches later, spliced it back to 2 wires. This second splice was completely corroded and came apart with the slightest tug. I clipped, stripped and crimped them back together and problem solved.

Here's a pic of the bad splice.



Here's a pic of the other splice (sorry for the fuzziness).

I wanted to say thanks to all of you who hung in there and kept making suggestions. A special thanks to Seang who was there from day one!!

Thanks for the shout out, and I'm glad you got it worked out, what an f'in nightmare. I will remember this fix for future references. They might have bridged the wires like that so that both injectors would get exactly the same signal, but that is just a guess. Thanks most of all for updating.

I also have a 1988 Jeep Cherokee and subscribe to several Jeep forums. Sadly, not everyone reports back on how they managed to resolve their issues. I wanted to make sure I "closed the loop" especially since this solved my problem. As always, YMMV but hopefully others with the same issue may find some benefit in my ordeal.

Always post what fixed it, that is how we all get smarter. Thanks, will add that to the bank of knowledge.

hi, I will have to check the production date on my truck, but I believe it's an 86. however, I pulled the tape and all insulation from my wiring, as I am having the same issue with my truck, half throttle, or around 2500 rpms, the truck just boggs down, like it's starving, or flooding, Z24i.... any ways, mine has 2 single wires running solid, no splices, no tie in points, no single wire as in your issue....... so I am still stumped... any other thoughts???? it's getting old! thanks in advance

Solder and heat shrink all electrical connections, I do not trust crimp on crap. Solder is permanent.

What else have you checked? I pretty much ruled out everything else by the time I got here.

if you are referring to me Saudade, I have replaced...... plugs, wires, coil pack, coil resistor, fuel filter, pulled codes, it's stating ignition system, code 21 i think..... I have no spark on the coil pack with the 4 wires going into it, the one with 3 wires going to it, which I believe is the one closest to the headlight is sparking just fine. But as stated the 4 wire one has no spark, from the coil or off of the plug wires.... don't know what's going on there, that is the coil and resistor I replaced...
Lets see..... what else have I done.... has a new rotor and cap, and.... hmmm... I can't think of anything else that I have done. I do know that when I bought the truck, the prev. owner said "I think it has a bad injector, I can't get it up past 50mph"...... well, I can get up to 85 mph, but it takes time lol.. and if I go half throttle, then it happens again, and I lose about 8mph fast! takes me a min to get back up to speed after that. any ways, long story short, it happens sometimes, and oh hot days, it's like it wont do it 90% of the time.... but when cold, it's extremely bad... I'm ready to throw a weber on and say to hell with the TBI set up, but that's kinda not a money option right now... just want the truck fixed... i love this truck!

on a side note, which coil pack runs which!? ? ? the 3 wire connects to??? intake or exhaust on the cap? I don't think it was hooked up right from the beginning from P.O. so I don't even know if it's hooked up correctly now! thanks for the info and help!

If I remember correctly the primary coil fires, then the secondary coil fires ten (crankshaft) degrees afterwards. If you are running on the secondary coil only, then it would be like having the ignition timing retarded 10 degrees farther than it should be, which kind of sucks. I forget which side is the primary/secondary, though.

I can't remember which is which either but at RPMs below around 2500, both coils ignite. This enables better flame propagation at low engine speeds. Around 2500 RPM, one of the coils is cut off (I think it's the exhaust) so only 1 coil sparks. So if the Int coil is bad (or the ign module attached to it), then the exh is the only one firing and will cut off at the RPM limit giving you the symptom you have.

Mine did the same thing a few years back and was the coil. This latest time around, it was the first thing I checked.

So with the engine running at idle, reach under and disconnect the ign module off the each coil. If both coils are firing, you should note a slight drop in RPM and maybe a bit of roughness in the engine running. Reconnecting should raise and smooth out the RPMs. If the engine dies, then there's the culprit. Now it could be the coil itself or the module or some other electrical thing. The coils themselves are the same part so you can simply swap them and see. I ran like this for a while until I could order the coil. If it's the ign module, they are not interchangeable and pretty expensive. You said you replaced them. Did you replace both sides?

thanks for that info! helps alot... no I only replaced the one side, the int side i think... the one with the four wire plug. I replaced it with a junk yard one, but monday I will trouble shoot and swap coils around and see it it's the module. where could one find a new one if it's bad? I tried autozone, and they looked at me with the deer in the headlights look.... duhhhhhh.... huh? lol... any ways, I will post my findings... ps... I can't get my tach to work either so it might be the coil resistor... (module) right?

Don't have a tach on mine so I can't help there. I'd look at http://www.rockauto.com/catalog/raframecatalog.php for the parts. Coils are cheap enough. The power modules are $100+ (ouch). If you have a JY nearby, you may find them there as well. I have quite a few locally but never seem to find one with a Z24i. Looks at a few parts sites, it appears that the early models with the VG30 use the same coil and module as the intake on the Z24. Maybe you can scrounge a set.

Not sure what the prob @ AZ was. They list the coil and modules as special order parts. That's where I got mine.

ok, update....

I have picked up another JY coilpack and module. paid 30 bucks, not bad... well, I get power to it, but... no spark!!! I swapped the wires off of the modules and it runs on either side, int or ex, but... only off of one module-the 3wire one. the 4wire one still gives me no spark through either coil. I have brand new plugs, wires, and cap. also have tried 3 different modules, and I know that it will not spark on the 4wire one trying to crank, or when running off of the exh. coil pack on either side, ie. int or exh. soo... now what? a ecu? any way to test that? how would I test the comp to the coil pack? this whole 2 sets of plugs on a 4cyl is absolutely stupid and pointless! I wanted to slap a weber on, but I will most likely have the same problems at rpm's of 2500 or more, so that's a no go right now... it's taking me about 1/4 of fuel to drive 63 miles.... and that's not good!


pls help me here guys. I am just stumped on this one.. I have exhausted all of my knowledge here and getting no where. thanks

ahhha hahahahahahah!!!! I got IT!!!!! I pulled my computer out, the pcm, ecu... what ever you wanna call it... any ways, after close inspection, I have a burnt capcitor, it runs to another resistor, and then all the way to the plug in pins.... I have ordered me one from Ebay for 199.99 shipped, and hopefully this will solve all of my problems... I will post up pics of what capacitor and resistor after PTC with my kids if anyone wants to know what ones I am looking at.

after I get the new ecu, I will be trying to fix this old one myself, and hopefully I can, I have done car amps, radios and other electronics, but this one is a bit more sensitive haha...

Nice catch. Keep us posted. Pics too!

I was at the pick and pull getting a new bumper and I decided to look in and the truck still had its pcm and I thought about you and wondered if I should grab it for future needs.

longtooth wrote:I was at the pick and pull getting a new bumper and I decided to look in and the truck still had its pcm and I thought about you and wondered if I should grab it for future needs.

Thanks for thinking of me might not be a bad idea, just in case I mess up the original one trying to fix it... these are some tiny capacitors and resistors!! I have dealt with some small stuff, but wow...... if you do pick it up, lemme know what they wanted for it, and if before you buy it, it's 7 screws and you can inspect the circuit board. it's pretty easy to spot a bad capacitor. the board will be black, and burnt along the printed wiring on the board itself. I will post up pics after I get my new one here and see if you guys can spot the bad spot. if you can here, you easily can with it in your hands.
and it has to be for the z24i MT, AT will not work, the only options asked when calling about one is, motor, trans, 2wd and 4wd don't matter, just motor and trans. mine is a 5spd, with the z24i. just a fyi....

I will keep you all posted!

AHHHA HAHAHAHA HA HAHAHAHA HAHAHAHA.... got my new "used" ECM and swapped it out, and......... viola!!!!!! tach works, it fires right up, and runs perfect on just the intake side coilpack! hahaha!!!! I will post up some pics of the burnt ecm in a few days, I'm working nights this week and don't have time to tear back into it, but when I attempt to fix it, I will post pics of that too! go me! the truck is slowly getting better and better every day!

Nice going!! Thanks for the followup and look forward to the pics

well took some photos today, here they are. sorry the pic quality sucks, my camera isn't the best, but it works haha... lemme know if you can't see them I can take better pics and point them out.

first, what the hell is this, and what does it do? it has the 3 wires into it... what is it for?


do ya see the burnt spot?


the other side...

Rogueroughneck, IIRC that is used to adjust idle CO levels.

Midnight Tech wrote:Rogueroughneck, IIRC that is used to adjust idle CO levels.

gotcha! thanks