renix problem! help please!

im try to fix a jeep thats been past through my family due to the fact nobody can fix it,

its a 89 cherokee larado 4.0l auto

the engine is brand new crate engine,

it starts right up but sputters when throttle is applied, if you drive it slow up to speed it sputters and bucks real hard at 30, only runs with map sensor vacumn line unhooked,

have tryed hooking up 3 different computers, didnt make a difference

items that have been replaced,

map sensor
IAC
TPS
fuel pump
all new vacumn lines
new distributer
wires
plugs

fuel pressure has been checked it right at spec

not sure any thoughts will help,
been trying to fix for the last year so now its up to you guys/gals

thanks

How are the grounds? In general, poor grounding causes huge headaches with the renix system.

Remove and clean the ground from the batt to the engine, the batt to the chassis, and the ground strap from the back of the block to the chassis.
MAKE SURE the block/chassis ground strap is in place. Sounds stupid, shouldn't be necessary, but that strap missing can cause a lot of weird problems.

thanks ill check on my next day off

if anyone else has ideas please post

I'm gonna bet the distributor is improperly indexed, but here'a how to address the grounds which need to be done at least once in the lifetime of a Ranix Jeep.

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

Since it is a new engine and will at least start, the most likely things to double check have to do with the ignition system. Verify the firing order. It is cast into the intake manifold. Second is to verify the distributor indexing. Turn the engine over to TDC as witnessed by the timing marks on the crankshaft harmonic balancer. Then pull the distributor cap. You have a 50/50 chance that you got the compression stroke. The rotor should be close to the #1 position. If it is on the other side of the cap, turn the engine over one more turn. Then move the crank to roughly 14 degrees BTDC. At this point the rotor should be pointing at the #1 position. If not, remove the distributor and insert it one tooth towards the #1 position. You will most likely have to use a long screwdriver and rotate the oil pump a touch so that the distributor can be reinserted.

old_man said:

Since it is a new engine and will at least start, the most likely things to double check have to do with the ignition system. Verify the firing order. It is cast into the intake manifold. Second is to verify the distributor indexing. Turn the engine over to TDC as witnessed by the timing marks on the crankshaft harmonic balancer. Then pull the distributor cap. You have a 50/50 chance that you got the compression stroke. The rotor should be close to the #1 position. If it is on the other side of the cap, turn the engine over one more turn. Then move the crank to roughly 14 degrees BTDC. At this point the rotor should be pointing at the #1 position. If not, remove the distributor and insert it one tooth towards the #1 position. You will most likely have to use a long screwdriver and rotate the oil pump a touch so that the distributor can be reinserted.

Click to expand...

This sounds to me very much like one tooth retarded.

I'm gonna bet the distributor is improperly indexed, but here'a how to address the grounds which need to be done at least once in the lifetime of a Ranix Jeep.

I'll cast my vote again for distributor indexing being off.

the jeep had acted like this before the distibutor change, that was the last part installed, have yet to check the grounds yet though

Do the ground refreshing first. I know people are skeptical about it but it's something that needs to be done on every Renix Jeep at least once in it's lifetime. The grounding system for the starting system and fuel injection system were woefully underengineered. The whole job without replacing/adding cables takes a half-hour or less. If you add cables, add 20 minutes and $20 to your effort. See how much better it cranks over and starts with the additional cables, too.

I hope someone did not damage the outer ring on the flexplate when they were installing the motor. It is possible to bend it and the cps will not get the correct signal. Good luck.

http://www.wheelingarizona.com/forums/files/flexplate_129.jpg

how old is the 02 sensor? this is kinda what mine did with a bad 02.

XJ longhouse said:

it starts right up but sputters when throttle is applied, if you drive it slow up to speed it sputters and bucks real hard at 30, only runs with map sensor vacumn line unhooked,

thanks

Click to expand...

This part caught my eye, replace the fuel pump. I hate it when Comanches start bucking. I drove one from Sacramento to LA to Sacramento. And the sputtering, all solved on my 1990 Long Bed with a new fuel pump.

The wire to the fuel pump was loose, and would come off and go back on. Replaced everything before finally buying the last of the fuel pumps from Bosch. Correct aftermarket should be available soon, if you need one, I did buy the last 8 they had.

I have never had a 4.0L buck unless it was the fuel pump.

JeepComancher

You do realize you answered a 5 year old thread don't you?