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renix running very rich

BPB

BPB

NAXJA Forum User
Location
Battle Ground, Washington
1990 mj 4.0 ax15. The exhaust smells like fuel, i burned through $10 of gas in the driveway firing it up trouble shooting.
I have a parts motor that ran perfectly about two weeks ago. I swapped the fuel rail (with injectors), throttle body (with sensors), distributor, every sensor on the motor minus the o2 sensor and ckps. All to no avail.
Next I pulled the ecu wiring harness, thoroughly inspected it, cleaned every contact and used dielectric grease on all connectors I even soldered a couple factory crimped connectors. At the same time I swapped egr valves and installed a new gasket.
It ran great for almost a minute then it went to crap.

Then I bypassed the inline fuel filter with fuel line and bypassed the ballast resistor. this didn't help and the fuel filter wasn't restricted. Any Ideas?
 
Last edited:
double check all the o2 wiring

Ecomike said:
This question comes up a lot in threads with O2 sensor trouble codes and threads about bad mileage. I hope to use this post (thread) as an FAQ about how to properly test mounted jeep O2 sensors and the wiring and related hardware.

For the Renix years, 87-90, the O2 sensor has 3 wires, 2 black and 1 orange. The orange wire (largest gauge of the 3) is the 12-14 volt power that comes from the O2 sensor heater relay on the passenger side firewall, and that powers the internal heater in the sensor so that the sensor can work at idle, and almost immedietly after start up. Loss of that power will hurt gas mileage even with a good O2 sensor.

One of the black wires is a common ground for the heater power and O2 signal to the ECU, so a poor ground will give a voltage feedback from the heater power input, to the ECU causing poor mileage even with a good O2 sensor.

The third wire, also black is a voltage feed wire, 5 volts, from the ECU to the O2 sensor. The O2 sensor is an O2 concentration sensitive variable resistor. At optimal O2 concentration the 5 volt input feed to the O2 sensor drops to 2.45 volts due to losses across the O2 sensor to ground. That same wire if disconnected from the O2 sensor will read 5 volts constant to ground.

At idle that voltage should read 1-4 volts oscillating quickly back and forth roughly once every second. At 2000 rpm it should run between 2 and 3 volts max, and is optimally running between 2.3 and 2.6 volts at 2000 rpm (in park). A digital meter can NOT be used for reading the O2 sensor voltage, but it can be used to test the ground and the 12-14 volts to the heater and the 5 volt feed from the ECU with power on and engine off. You must use an old style analog meter with the needle gauge on the display to see the voltage swing back and forth with the engine runing.

If the O2 sensor readings are not right, say they read 4 volts or 1 volt steady, you have a problem. BUT before you blame the O2 sensor make sure it has good wiring, and make sure the proper voltage is feeding it, by turning power on, engine off to read the engine off voltage feeds (12-14 volts on the orange wire, and 5 volts on one of the two black wires), and ensure the ground wire (power off) reads less than 1 ohm to the battery negative post.

A leaky exhaust system or leaky fuel injector(s), or bad compression, bad rings or leaky valves, bad plugs, wires, cap, rotor, HV coil, and so on, or combination of these, can also cause a lean or rich condition that gives you high or low O2 sensor readings that are not the O2 sensors fault, so try and verify those other items also before buying parts like an O2 sensor to fix your problem.
Click to expand...


you could also try a different coil.

Haven't talked to you in a while, how much have you driven it since it was back on the street? did this start suddenly while driving it or has it sat for a while and you just now started it and noticed it? if that doesnt work cant you still take whitney's jeep up this weekend?
 
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I am assuming that the engine has been maintained for the sake of my post- like the cap/rotor/wires, coil, tbody are all in good shape...

Check for DTCs.. likley won't get any with a renix unless the fault is happening right then/ is an open/short sensor voltage issue.

check all the grounds, double check the map vaccum source, check the signal integrity of the MAP and TPS sensors- all are 5v reference three wire signals. Pay particular attention to the ground lead of the TPS... often times running another ground will clear mysterious renix issues up.

Do a fuel pressure check see what pressure you are running- regulator/pump issue.
 
cruiser54 said:
Got vacuum to the MAP sensor?
Click to expand...

Yes, it will die when the vacume is disconected, I have strong vacume at all vacume hoses, and I went through two bottles of brake clean searching for a vacume leak.

streetpirate said:
double check all the o2 wiring




you could also try a different coil.

Haven't talked to you in a while, how much have you driven it since it was back on the street? did this start suddenly while driving it or has it sat for a while and you just now started it and noticed it? if that doesnt work cant you still take whitney's jeep up this weekend?
Click to expand...

I'm out for this weekend. I might come up for the night, she doesn't get off work till 1:30 saturday so we would be too late for wheeling. Oh and I have tried two coils and ignition modules. Also it started doing this after sitting about a month.

lucky14 said:
I am assuming that the engine has been maintained for the sake of my post- like the cap/rotor/wires, coil, tbody are all in good shape...

Check for DTCs.. likley won't get any with a renix unless the fault is happening right then/ is an open/short sensor voltage issue.

check all the grounds, double check the map vaccum source, check the signal integrity of the MAP and TPS sensors- all are 5v reference three wire signals. Pay particular attention to the ground lead of the TPS... often times running another ground will clear mysterious renix issues up.

Do a fuel pressure check see what pressure you are running- regulator/pump issue.
Click to expand...

I will be doing a fuel pressure check, I have gone through two brand new sets of wires plugs cap and rotor. I noticed that there was no change when disconnecting the fpr. I am going to spend some time with my power probe this friday.
 
Oh and as far as tdcs I haven't had much luck with using "the brick" on it I wind up getting the same info that I can get with my multimeter or power probe and I have those at home
 
I believe so. The problem is that 3 wires connect to one wire with a crappy crimp in the harness near the injectors. That single wire then travels to an area near the MAP and then the MAP, ECU, and the diagnostic connector are crappily crimped together. I have found anywhere from 38 to 74 ohms of resistance in that circuit just by wiggling the harness with the ohmmeter hooked up. Easy to fix. Something not to overlook. Wiggle the harness while testing.
 
I'd get that fuel pressure reading. Should have 31 psi of fuel pressure at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. And be sure that the vacuum line leading to the FPR is pulling good vacuum and is not wet with fuel, which can indicate a ruptured fuel pressure regulator.
 
I actually soldered that connection when I had the harnss out and cleaned all of the ground terminals, stud and nut with 180 grit. Ill try to get my hands on a preasure tester tomorrow. There is no fuel coming from the diaphram.
 
cruiser54 said:
What connection did you solder?
Click to expand...

Both of the crimped connections in the wiring harness. I pulled it apart on my kitchen table and looked for broken wires and bad connections. while I had it apart I soldered both of the crimped connections that I found.

So when I got home I fired it up and it ran great for about two minutes and as soon as the idle dropped it went back to crap. I am thinking that the new to me egr valve might not be functioning properly, I think that I might make a block off plate for it just to test. I also left it setting with the battery disconnected as well so the ecu probably would have reset.
 
They don't reset. Do this with the EGR. At idle, pull the diaphragm towards you with your fingertips. If it dies, EGR is good. If not, it's probably hanging open. Or, try this:

TESTING THE EGR VALVE FOR 87-90 4.0 ENGINE
Valve Opening Test
1) With engine at normal operating temperature and at idle,
rapidly open and close throttle. Open throttle sufficiently to obtain
at least 1500 RPM. Movement should be noticed in EGR diaphragm.
2) If diaphragm does not move, probable causes are: faulty
vacuum signal to EGR, defective EGR diaphragm or defective
backpressure sensor diaphragm (if equipped), or leaks in vacuum lines
or connections.
Valve Closing Test
1) With engine at normal operating temperature and at idle,
manually depress EGR valve diaphragm. RPM should immediately drop,
indicating that EGR valve is not leaking and had been properly cutting
off exhaust gas flow at idle.
2) If there is no change in RPM and engine is idling
properly, exhaust gases are not reaching combustion chamber. Check for
plugged passage between EGR valve and intake manifold.
3) If engine idles poorly and RPM is not greatly affected by
manually moving diaphragm up, EGR valve is not closing off exhaust gas
flow. Check for carbon between pintle, leaking EGR valve gasket or bad
EGR valve.
***************
 
I took the worst cell phone video ever. so what it shows is there is a very small rpm change when manually operating the egr, disconnecting the map sensor kills it, disconnecting the fpr doesn't do anything, disconnecting the tps and iac does nothing, disconnecting the o2 sensor raises the idle a bit. so just for the hell of it here's the video.



Click it. Sorry I need a new idler pully
 
I'd like to see actual fuel pressure readings.

Holding the EGR open usually has a rather pronounced effect on idle. You're saying it doesn't on your Jeep?

Humor me and do this:
Cruiser’s Renix Jeep Sensor Ground Test
Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector
of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post.

Wiggle the wiring harness near the injectors and near the MAP sensor while observing the meter.
If you see more than 1 ohm of resistance a modification/upgrade to the sensor ground harness will be
necessary.
This project will require soldering skills.
 
Ok have fp guage, vacume guage, and the "brick" hooked up. I have 15 in of vacume, I have 31 psi fp idle and 39 with the fpr unhooked. 1.9v map, .64v tps, fuel trim 128, and it just ran out of gass again!!!! That was another $10 I'm putting in 20 this time
Its almost like its on life support and I'm about to pull the plug
43bd6b5c-0230-dd95.jpg
 
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