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Renix woes for 1988 XJ 4.0/auto

Will it rev high in neutral? If not, you could have a distributor indexing problem. I even had a CPS that would limit the engine to around 1500 rpms once.

What color is the tailpipe. It should have a black coating. If it is light grey, it is running lean.
 
When you crack the throttle, does the fuel pressure change?
 
tail pipe is black. throttle does not go much beyond idle. as iin idle fuel and spark are there but wont rev high. idles fine with a little shake, i can deal with for now. i dont think the fuel pressure drops, gage died and cant re check. but does have new pump and filter.from a year and a half ago.
 
Just reread this end to end

1) You need to confirm fuel pressure and flow capacity is still there to maintain higher engine rpms. Pumps go bad right off the shelf, and fuel lines in the tank come loose.

2) It sounds more and more like exactly what I had last year, The shear pin on the gear at the bottom of of my Distributor shaft was loose (finally broke, sheared off) and I could spin the rotor around by hand. There should be no rotational play in the rotor turning it by hand. Mine had a bout 3/8" side to side just before it broke.

Second the distributor you have may need indexing, I even had to cut the location ear off of mine on the brand new one, like so many others here to index the new one as it was defective off the shelf new, because of OEM Factory Cam shaft mistakes over the years by AMC-Jeep on these jeeps. Did you say you replaced the engine? Distributor?

See if the rotor on the distributor can be rotated rationally or if it has any side to side play in the shaft (bad bearings). If it has more than 1/8" in rotational SLOP, or any side to side play replace it.

Either way, take a used cap and make a cut away view window and follow cruiser54's Indexing the distributor instructions on his website blog. There are no short cuts to his instructions, LOL, I tried. Buy a new cap and rotor and used the old one for making the window Cap tool. Makes the indexing super precise!!! And that makes a huge difference. Contrary to urban legends, the ECU can not compensate for a spark jumping the wrong plugs!!!

165828d1357386046-ho-4-0-swap-renix-no-spark-renix-dizzy-indexing.jpg
 
so before i had to fixed...well 60 percent of the time anyways. it ran good and strong. when it ran bad, i shake the harness and it come back to good. i replaced the harness and got rid of a lot of crap. but now back to no power. the reason not messed with ignition, is this is not an ignition problem. it is a sensor not telling the cpu to deliver problem.
 
IIRC you disconnected fuel/spark to one cylinder at a time with no change? Have you tested each fuel injector pigtail with a Noid light?

Do what you want, If it was me, I would set the Crank to TDC, and pull the cap and see where it is pointing, and see if the rotor has slop in the rotation.

Also the ECU may have an issue if the harness had a short and damaged the ECU.

Have you tried running and driving with the O2 sensor disconnected????

Have you confirmed that the O2 sensor heater is good (about 8 ohms) and that the heater wire, orange has 12-24 volts from the relay???
 
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How's the tube from the throttle body to MAP sensor?

It has to be perfect.

Any change if you unplug the MAP sensor?

How much voltage at the fuel pump wire connector?
 
Ecomike said:
IIRC you disconnected fuel/spark to one cylinder at a time with no change? Have you tested each fuel injector pigtail with a Noid light?

Do what you want, If it was me, I would set the Crank to TDC, and pull the cap and see where it is pointing, and see if the rotor has slop in the rotation.

Also the ECU may have an issue if the harness had a short and damaged the ECU.

Have you tried running and driving with the O2 sensor disconnected????

Have you confirmed that the O2 sensor heater is good (about 8 ohms) and that the heater wire, orange has 12-24 volts from the relay???
Click to expand...
o2 is new and works fine. ecu swap and no change
 
Ecomike said:
IIRC you disconnected fuel/spark to one cylinder at a time with no change? Have you tested each fuel injector pigtail with a Noid light? while wiggling all the harness wires?

Do what you want, If it was me, I would set the Crank to TDC, and pull the cap and see where it is pointing, and see if the rotor has slop in the rotation.

Have you tried running and driving with the O2 sensor disconnected????

Have you confirmed that the O2 sensor heater is good (about 8 ohms) and that the heater wire, orange has 12-24 volts from the relay???
Click to expand...
 
i sorted out my injectors ,thanks to Cruiser's info on which color wire goes where. they are all working as well.
when i was messing with this before, i got a new o2 sensor.
 
Gunter said:
i sorted out my injectors ,thanks to Cruiser's info on which color wire goes where. they are all working as well.
when i was messing with this before, i got a new o2 sensor.
Click to expand...

OK, let me spell it for you in black in white, as they say.

A new O2 sensor is worthless if it is defective out of the box, and for bad brand-(China) quality, this is common.

Bosh is the Best for Renix (I think you said you bought Bosh?)

BUT!!!!!

IF the O2 sensor has a ground wire problem (over 1.0 ohms to ground at the Bat negative post) or is not getting 5 volts from the ECU, or not getting 12-14 volts from the power relay for the heat built into the O2 sensor, it CAUSES YOUR PROBLEM!!!!! Bad relay, or bad wiring!!!

Is that clear now???:twak:

:laugh3:
 
If you fixed the wiring harness problem, that made it switch running bad-good-bad when you you shock the harness, then you have a second problem!!!!

" I would set the Crank to TDC, and pull the cap and see where it is pointing, and see if the rotor has slop in the rotation.

Have you tried running and driving with the O2 sensor disconnected???? That is an easy way to see if the O2 sensor/wiring/ECU/Heater realay system is causing the low power and random miss!!!! Your problem is a common one for a wiring..............................................O2 sensor cause!!!!!!

Have you confirmed that the O2 sensor heater is good (about 8 ohms) and that the heater wire, orange has 12-24 volts from the relay???"
 
ok the voltage is 14.86 when running and no difference when revved.
and ohms show nothing when i connect to the 3 wires on the O2 sensor.
so O2 is crap, dont have a spare.
 
Gunter said:
and ohms show nothing when i connect to the 3 wires on the O2 sensor.
so O2 is crap, don't have a spare.
Click to expand...

Sounds like it, if I understand what your saying??

Using The O2 wire that connects to the orange harness wire that had 14 volts, and
the black ground wire (ground) on the O2 sensor should read about 8 ohms when disconnected from the harness (IIRC*)


Read the thread I created for this 10 years ago for more blow by blow details of testing both sides, the harness wiring to the ECU and the O2 sensor.

http://www.naxja.org/forum/showthread.php?t=1012701
 
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