87cherokee chief

1987 4.0,auto.been chasing a rough idle for a few days,fine when on the gas,but up & down at a stop light.checked all grounds cleaned ic,& throttle body etc,recent plugs cap rotor.
did the test on the tps,its a 3 pin harness,heres what I got.2.58 a to b,and 0.03 b to c terminals probing from the backside of the harness.so if I divide 2.58 x3,that gives me,0.86.is this correct???anyone help???both #'s seem pretty low.........

cruiser54

Uh, weird math.

Use this:


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: With the Key OFF, and 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 where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, 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 only a flat three-wire TPS mounted on the throttle body and it provides data input to the ECU. It 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. Loosen both T-20 Torx screws attaching the TPS to the throttle body and rotate the TPS until you
have achieved your desired output voltage. Tighten the screws carefully while watching to see that your output voltage remains where it is supposed to be. If you can't achieve the correct output voltage, replace the TPS and start over.
Sometimes, after adjusting your TPS the way outlined above, you may experience a high idle upon starting. If that happens, shut the engine off and reconnect your probes to B and C. Start the engine and while watching your meter, turn the TPS clockwise until the idle drops to normal and then rotate it back counterclockwise to your desired output voltage.
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, as outlined above—FOR ALL 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. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. 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.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the square four-wire connector side of the TPS.
If you have ENGINE ISSUES check the flat 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.
Revised 09-22-2012

cruiser54

BTW, ever done a connector and relay refreshing or c101 cleaning?

87cherokee chief

thks cruiser I did a calculation I got off the net,and also came across yours for the tps.did your calculation 2.58 by .17,came up with 0.43,can only get mine to adjust up to 0.05.it was at 0.03 to start.say time for a new tps..........still running lean,& stumbling.
did the c101,whats the relay refreshing??

cruiser54

Why is your input voltage so low? Should be a shade under 5 volts.

Click on the "pink link" in my signature and look at post # 3 for the connector refreshing.

87cherokee chief

thanks cruiser,dont know why volts are so low.did go out & clean the c101 again........no change.

cruiser54

This has to be addressed before going further. Flat connector, left plugged in, key on and backprobed, right? As in the photo below?

87cherokee chief

as in pic yes.key on,B & A,im getting 2.59,B & C im getting 0.03.

cruiser54

Got another meter to try?

87cherokee chief

no I don't,thought of that.hooked it to battery earlier,13.8 volts running so,it is working.

cruiser54

Something isn't right. That voltage supply comes form pin C15 at the ECU, THROUGH THE C101. Light blue wire.

87cherokee chief

ill do some tracing tomorrow see what I can come up with,probubly in the c101 im guessing???

austinjoe13

Bad sensor ground maybe?

cruiser54

Ya know. That's a good thought 87cherokee chief. Probe A with your red probe and put the black probe on a ground other than the one in the TPS plug and see what you get.

And yes, the 5 volt reference voltage comes to the TPS through the C101.

austinjoe13

I haven't taken my circuits classes yet but wont the supply only put out as much power as the ground can receive? Or maybe there's a power leak?