Test #1
260,000 miles

HC 126ppm w/ limit of 220ppm
CO 6.6% w/ limit of 1.2%
CO2 10.33%


Test #2 (test conditions at noon were ~60degrees with 95+% humidity.
262,000 miles
HC 87ppm w/ limit of 220ppm
CO 4.06% w/ limit of 1.2%
CO2 11.59%



Between these tests this is what I have done.
Been running premium fuel only.
Got radiator and hoses replaced.
power steering pump and idler pulley replaced. The pulleys on these both literally exploded some 300 miles apart.
Maybe 1/3 bottle of seafoam through the vacuum lines.



So the high CO from internet surfing makes me believe that it is only the engine running rich as the HC are well within limits and actually decreased and more CO2 is being produced which is good as well. Makes me believe that the CAT is working and getting unwanted elements turned into CO2, H20, etc. Currently ~14mpg, usually less with 60% freeway speeds. The most likely candidate for being bad is the CO2 sensor with the MAP sensor being a good possibility as well.

Tomorrow I recon I will get these tested out after school. Unplug them and see if anything changes.
I got my Jeep back the other day from the radiator and hoses being installed. I have the Neon fuel injectors installed, so maybe I didn't reset the computer properly and with them having my jeep in the shop for 4 days, the battery might have been unplugged enough to properly reset the computer?


Any thoughts?
1989 so it has the Renix system.

 

I think the main function of the EGR valve is to limit formation of Nitrogen Oxide. Still, since you are having an issue I might think you would want to make sure its working right. Cruiser, who actually worked at a Jeep dealership now and then mentions that the grounding system on the Renix jeeps was under designed. By going through and cleaning it all up, everything "gets happier", sensors, ECU & TCU. Makes them just plain giddy!

Also I read that the O2 will go rich as it ages/fails. The test here is high on MY list as my 89-90 (with just over 260K), use to get better mileage. Booger that something that will probably save me money isn't in the budget right now!
http://www.naxja.org/forum/showthrea...ht=sensor+test

Also cleaning the TB and IAC should be done now and then.

Here's one of his writeups;


Renix Ground Refreshin
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.

 

First test it was probably not warmed up enough. Way too rich causing HC to jump up.

Second test shows a tad rich, HC is under control.

EGR has nothing to do with it.

Check that the cat is still working right. Use an infra-red thermometer to measure the cat's temps. Run at 2000 RPM for 2 minutes, go under. measure temp at the inlet vs. the outlet of the cat - should be about 100 degrees HOTTER COMING OUT.

Could be the Oxygen sensor is getting old - they get "tired" after about 100,000 - 150,000 miles.

But you also mentioned mileage is down. Look for an exhaust leak ahead of or near the O2 sensor. The exhaust pulses - from pressure to vacuum, if there's a leak fresh air with lots of O2 gets pulled in on the sensor, telling the computer it's too lean, a lie! The computer richens it up - now CO is too high and mileage goes down.

To check for exhaust leak - squirt a little oil, carb cleaner, seafoam etc down the throttle body to make it smoke, stuff a rag in the tailpipe to slightly pressurize the exhaust, go under with a strong pencil beam flashlight to find where smoke comes out where it shouldn't.

I no longer have my smog license - dropped it when I sold my last repair shops - high performance dyno tuning and smog, but I still remember!

Yes, you can have high performance, good mileage and still have low emissions.

 

The first test I was actually freaked out because the thing was overheating bad. When driving temps are fine, but if sit for a while the temps would go up. So it was pretty hot at testing time as there was a long line. Usually is never a line and both times I have gone, there has been a stupid line.

 

What should normally happen when one removes the IAC power connector? Mine doesn't make any difference what so ever.
I was removing some power to sensors and removing vacuum lines to see if they even had vacuum out of all I touched (not much) the IAC made zero difference.


Whenever the Jeep starts up, starts normal and idles at ~650rpm. Little throaty and a little rough, which I have heard the Neon injectors tend to do.
But once it gets a little bit warm, rpms go to and stay at 1250rpm. When in drive, it will go down to about 1000rpm.

 

You might well just end up chasing your own tail if your grounds are not good.

You might want to check a couple of the easy to reach manifold bolts. If you find a couple loose don't crank on them! You pull the air cleaner and go over them all a few times starting around the middle working out. Look and listen for vacuum leaks. I use little blasts of starting fluid to check. If you hit one the RPM will change. Make sure the little tube from the TB to the map is A1. It's brittle and will make it run rich if it leaks.

Btw...The Renix ECU doesn't strore or remember anything, nothing to "reset".

I've never adjusted a TPS. I would though if my idle was goofy and I had ruled out vacuum leaks.

And Cruiser's Renix TPS adjustment.

RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned.
It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: 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.
If you see more than 1 ohm of resistance some modifications to the sensor ground harness will be
necessary. The harness repair must be performed before proceeding.
I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body.
This manual transmission vehicle TPS provides data input to the ECU. The manual transmission
TPS has three wires in the connector and they're clearly embossed with the letters A,B, and C.
Wire "A" is positive.
Wire "B" is ground.
Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors..
Note the voltage reading--this is your REFERENCE voltage.
Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your
OUTPUT voltage.
Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For
example: 4.82 volts X .17=.82 volts. Adjust the TPS until you have achieved this percentage. If
you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION:
RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-
wire connector, same as the manual transmission vehicles have, and it is tested the same as the
manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector clearly embossed with the letters
A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module.
Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your
REFERENCE voltage.
Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT
voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage.
For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage.
If you can't, replace the TPS and start over.
So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and
the other side feeds the TCU. If you have TRANSMISSION issues check the four-wire
connector side of the TPS. If you have ENGINE issues check the three-wire connector side of
the TPS.
For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is
stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.

And there's this IAC cleaning:
IAC CLEANING 88

The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

 

I would start with a new cap, rotor, champion plugs and wires then go from there.

 

First test - overheating - the computer richens the mixture hoping it will cool it down - thus the high CO.

2nd test - could be just starting to richen it if hot.

Did you measure the cat's temps? A good cat will burn off excessive CO. That's why they are there!

Did you check the exhaust for leaks with the smoke test?

Before testing again, drive it till you need gas. Put in fresh gas - the additives evaporate in a week's time - needs to be fresh.
AND - dump in a pint of DENATURED ALCOHOL in the tank. It helps it burn a little better - helps if marginally failing.

Denatured alcohol is available at hardware or paint stores - used as a cleaning solvent.

No, not Jack Daniels - that's a different alcohol!

(Denatured for the Jeep, Jack for you!)

Let us know how it does.