I'm new to this forum and to jeeps in general. Just bought my first Cherokee about 4 hours ago. 90 Cherokee Pioneer with the 4.0. All stock except for a 4" rough country lift.

On the fixer up list is the emissions light showing on the dash. It's on constantly, even without the engine running. Not sure if it's related, but the jeep also sputters and dies sometimes at low idle when you start to press the accelerator. Prime example is coasting down to a speed bump: you slow down to go over the bump and then touch the gas...sputter...dies. Not every time tho.

Starts right back up and runs fine. As it's pre-OBD days, I don't have any idea if there is a code to read or not.

What should I do to narrow the problem down?

Thanks in advance for the help.

 

O2 sensors

 

Wat year is it also. There's a timer box under the dash I would just pull it out will Take the light away for sure if its 80s to 91 if I remember. Righ

 

That emissions light is just a timer. It comes on after a certain number of miles, the idea was the O2 sensors were good for 75K or so and the light was to remind you to replace them when that mileage rolled around. (I'm not sure of the exact mileage, just using 75K as an example)
They can't be reset, they were replaced when they tripped on. Or you can just yank timer module or the bulb.

The sputtering could be several things, I'd start by checking your Throttle position sensor for proper operation. Also a good time for the standard tune up stuff, and ground/c101 connector refreshing..

 

Ground c connector. ? New one for me Wat. Is that

 

Ground refreshing and C101 connector. I probably shouldn't have used the / as a separator, lol. It isn't very clear.

 

Where the hell is it at

 

Like it was already stated, all the light is on for is to remind you to do emission related nonsense. The box looks kinda like a big timer in a clear case. I just got done taking my buddies out. Its right under the driver side kickpanel. As far as sputtering and dying, i would start by checking the TB and see if you have a lot of carbon build up. If so, shoot some cleaner down it, or do what i did on a day off and pull it out and clean her up real pretty. Unless someone else has an easier starting place....

 

Sea foam

 

For some reason, I was thinking that the ground cleaning and c101 connector was a pre-89 problem. That the connector was eliminated in 89 and 90 models. Am I wrong about that?

As far as this "timer box" is concerned, what is involved in removing it? Do I need to splice wires back together or can it just be cut out with no other effect?

 

Just drop the lower dash

unbolt that box Pull the connector out. Throw it in garbage. Or scrap pile your finished

 

Unhooked the timer box and lite is gone. Thanks!

Had loose steering column so I took that all apart and tightened it up.

Cleaned the throttle body and air box. Still has the occasional tendency to die. I'm going to try the O2 sensor today and see if that does it.

 

I put in a brand new Bosch O2 sensor and took it for a 3 hr drive up in the mountains. It still has the tendency to stumble after letting off the brakes and applying gas, but it didn't die. This only happens when slowing down for an obstacle and then proceeding to speed back up. It does not do this when starting from a stopped position.

Clean throttle body and new O2 sensor. Any other ideas?

Thanks for the input so far!

 

Throttle Position Sensor and/or Idle Air Controller

Idle Air Control cleaning don't touch the pintel.
The is a post for the IAC cleaning, sorry I don't have a link to it.

Here's the info for TPS I do have:

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.


TPS Test

The TPS signal is fed to the PCM and the TCU, they both use it.

There are three wires on the TPS connector....ground, +5v power, and signal output.
Measure the signal output voltage, it's the center wire in the plug. Orange wire with a blue tracer, IIRC.
You'll have to do this by backprobing the connector while it's plugged in, or using a small pin to pierce the insulation. Key ON, engine OFF.
It should start off very low and increase smoothly as you open the throttle, with no skipping, jumping or dead spots.
And old-fashioned analog voltmeter with the moving needle is excellent for this. Should see a smooth sweep from <1V to just under 5V.

Specs are 0.26v at closed throttle to 4.49v at WOT.
The exact values are not critical for TCC lockup purposes, the TCU looks for a relative decrease, indicating you've taken your foot off the accelerator, or an increase when you step on the gas.