Renix system Need Help

I have issues. NEED HELP
The Cherokee works like a dog. It idles OK but upon tip in throttle it skips badly and backfires through the exhaust. Full acceleration it revs OK as well. Its a renix system and I changed a whole bunch of stuff to eliminate components. The stuff I changed are throttle body, cause the tips shows a part throttle at 0.27v. Intake air temp, wire broken. Crank sensor, watching it with lab scope it spikes at different times (and not a reference spot). Ignition coil/module, cause I had one so I used it. O2 sensor cause it was dead. Swapped computer and still no change. Fuel pressure is 30 psi Idle and it still acts up with regulator unplugged and 40 psi. Besides the Skip is too fast for fuel so thats why I'm concentrating on fire. At idle the spark will jump an Inch with blue spark, when its backfiring and running rough the spark will hardly jump 1/8 - 1/4 Inch this I think is not normal and might be a problem ? and its the same with the other swapped coil/module. Any suggestions and help is needed as for all this work done so far is for nothing.

Have you checked the spark plugs? I had plugs on 2.5 engine start misfiring. I changed the spark plugs ran great. Good Luck.

Yes also replaced spark plugs. added so much to list forgot to add plugs lol

I've heard rumor that the coils on a renix can be problematic.

Never had one go out so I do not know if what you see is the symptom of a dying coil.

might sound dumb, but might want to double check your firing order, maybe with all that swaping around you mixed two of the cables up, and they are on the wrong cylinders, i did this once, took me quite a bit to figure it out.

You didn't mention the EGR, but that can cause stumbles/misses.

Yee Haa
Found and fixed the problem myself.
Turns out the distributor was out of time. You cannot install them straight up I had to grind the lock tab off and advance the dist about .040" to get rid of the Skipp. Now it runs really good.

Comanche Devil said:

Yee Haa
Found and fixed the problem myself.
Turns out the distributor was out of time. You cannot install them straight up I had to grind the lock tab off and advance the dist about .040" to get rid of the Skipp. Now it runs really good.

Click to expand...

Been there and done that, don't know why I didnt suggest it! Mine runs like a champ since, the plugs are perfect when I pull them. I'm getting 17 in town and 22 highway and no detonation now(my knock sensor is unplugged as well, don't need it since there is no sign of detonation/pinging) and plenty of power!

See post 33 on this thread from a few months back;http://www.naxja.org/forum/showthread.php?t=937822&page=3&highlight=cutting+the+tab+off+distributer

Looks like this is going to be my next try.

SO far, I have replaced and tuned the TPS, replaced the O2 sensor, replaced all vacuum lines, plus, wires, cap, and rotor, and I still get stumbling right at 2k rpm, and backfiring through the intake. Its getting really, really aggravating.

I think I will pull the distributor tomorrow, and see what I can do. I am nearly at wits end.

liliysdad said:

Looks like this is going to be my next try.

SO far, I have replaced and tuned the TPS, replaced the O2 sensor, replaced all vacuum lines, plus, wires, cap, and rotor, and I still get stumbling right at 2k rpm, and backfiring through the intake. Its getting really, really aggravating.

I think I will pull the distributor tomorrow, and see what I can do. I am nearly at wits end.

Click to expand...

Check the EGR valve first, those are classic symptoms.

Will do....

As a way of eliminating or identifying the EGR as the issue, is there an issue with removing the EGR valve, and blocking it off for troubleshooting purposes?

liliysdad said:

Will do....

As a way of eliminating or identifying the EGR as the issue, is there an issue with removing the EGR valve, and blocking it off for troubleshooting purposes?

Click to expand...

For trouble shooting, I made a block off plate by using a gasket as a templete out of 1/8" steel. It took maybe an hour to make the plate. I put the platein between the EGR and the intake and sandwich the plate with 2 new gaskets($4.50 each at Advance Auto). then plug the vacuum line and that completely takes the EGR out of the equation. You will be surprised how much better it will run.

If that makes it better just replace the EGR, EGR solonoid, and make sure the lines are in good shape and that the "tube" is not rotted out.

I left my egr in and plugged the vac line and disconnected the solenoid...just be sure the egr valve seats and isnt stuck open so it doesnt create a vacuum leak at the manifold.

OK, I took the EGR valve off, and fab'd a block off plate.

The Jeep idles much better, and drives much, much better....that being said, I still have the backfiring through the intake. It is much less pronounced, and less often, but its still there.

You mentioned earlier that the fuel pressure was 30 at idle and 40 when you took the vacuum off the regulator. You should have 40 at idle and when you pull the regulator it should up to a about 44. I had the same symptoms last year and changed everything that I could think of except the fuel pump. I changed the pump and all the problems went away.

Before changing the pump I checked the pressure and it was at 28 lbs and with the reg un hooked it was at 35.

Changed the pump it was at 40 and 44. What happens is it goes into a lean condition and when it heats up it goes into default open loop. The computer does not know what to do.

Hope this helps.

Leep

30psi @ idle with regulator plugged in.
39psi @ idle with regulator unplugged.

I dont know where you got the 40psi/44psi number.........The renix is supposed to be what I typed above.
How does a failing pump make the motor go into a lean condition???

Hi all Thanks for the help.
Cherokee is fixed and running fine. It was the dist out of sync to crank sensor. Just ground off the locking tabs and advanced it .040 and its working perfectly, lots of power and scanner data is bang on far as O2 readings and short term fuel delivery, map readings. Gas readings at 2000 rpm are also bang on as well. Didn't wright them down to post here but they are good.
Thanks again
Comanche Devil

OK, I think I fixed mine.

I replaced the coil with another factory Renix marked coil from the parts Jeep. I could tell an instant increase in idle quality, but the backfire through the intake was still there. I went ahead and pulled the distributor from the parts Jeep as well.

When I loosened the hold down on my distributor, lo and behold, the ears had been cut off...I didn't even attempt to jack with that one, which was a reman unit anyway. I dropped the distributor from the parts Jeep in, and...voila....healed.

Driveability is 100% better, idle is smooth and even, seems all is well, with one caveat. At part throttle, I still have some sluggishness, before it really kicks in. I have a gut feeling I have some fuel pressure issues that were masked by the ignition troubles. I am gonna put a gauge on it tomorrow,and see what it says.....