1993 cpi 4.3 liter stumble

[big cherokee]

well my truck has run good with the 4.3 swap in it have had it out on the trail twice now and no problems.

but 2 times now driving it around town when i got to accelerate hard it will just choke and wont go anywhere.

this is not a missfire as new plugs wires and cap and rotor and it does not feel like a missfire.

has anyone seen the cpi injectors go bad on these and cause this issue, i have installed a new fuel pressure regulator and non of the spiders were leaking

the only thing i can figure is the resistance in the injector goes to high when the engine gets warm and will not operate properly, it runs like it is very rich

now i know this has only happened twice but i dont want it to happen on the trail

any help would be very appreciated.


thanks
ryan

 

[jsudar]

It's been a while since I messed with those, but I remember the CPI injectors being real pieces of crap. They have poppet valves at the tip of the injector that gets clogged easily. The only thing I ever had luck with (beside replacing them) was really strong injector cleaner-- not the kind you dump in your tank, but the kind you hook up to the fuel rail and run the engine on it. A shop I worked at had a canister you filled with cleaner and used shop air to provide the pressure to run.

VW used a similar poppet style injector on their L-Jetronic systems, but ran a lot more fuel pressure to blast crap out of the poppet valves. That's were GM got the idea.

 

[jsudar]

It's been so long I can't remember, but if that engine has a mass air flow sensor, clean it. If the filament in the MAF gets really dirty, it can cause symptoms like you described. Use brake clean or something and compressed air. Be very gentle with it though.