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1988 Jeep Cherokee 4.0 6cyl
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Discussion Starter #1
1988 4.0 Renix

Pretty straight forward. I'm picking up my new IAC and TPS today. Do I HAVE to adjust the TPS sensor? Or can I just plug it in straight from the box.
 

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I would at least reset the ECM. Just pull the battery cables off. Touch them together for about 10 seconds then reattach. I would also suggest changing the sensor while the cables are disconnected.
 

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There is a procedure for that

CRUISER'S MOSTLY RENIX TIPS
RENIX TPS ADJUSTMENT
OCTOBER 30, 2015 SALAD192 COMMENTS

Before attempting to adjust your TPS, there are a few things that need to be done.
  1. 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.
  2. With the KEY OFF, and using the positive (red) lead of your ohmmeter, set on the lowest scale, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself.
  3. 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. It is covered in detail in Tip 6.
TPS ADJUSTMENT FOR ENGINE ISSUES
Both Renix manual and automatic transmission equipped XJs and MJs have a flat three-wire connector to the TPS which provides data input to the ECU. The three wires in the connector are clearly embossed with the letters A, B, and C. Wire “A” is positive. Wire “B” is ground. DO NOT UNPLUG THE CONNECTORS!Backprobe 2
  1. KEY ON, measure voltage from “A” positive to “B” ground by back-probing the connectors. Note the voltage reading–this is your REFERENCE voltage.
  2. KEY ON, back-probe the connector at wires “B” and “C”. Measure the voltage. This is your OUTPUT voltage.
  3. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts.
  4. 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.
  5. 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.
TPS ADJUSTMENT FOR AUTOMATIC TRANSMISSION ISSUES
Renix automatic transmission-equipped XJs and MJs 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 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.
First off, DO NOT UNPLUG THE CONNECTORS!
  1. KEY ON, measure voltage between “A” positive and “D” ground by back-probing the connector. Note the voltage. This is your REFERENCE voltage.
  2. Back-probe the connector at wires “B” and “D”. Measure the voltage. This is your OUTPUT voltage.
  3. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts.
  4. 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 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. The square 4 wire connector is just not used.
 

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Make sure you face the corner :D
 
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1988 Jeep Cherokee 4.0 6cyl
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Discussion Starter #6
So I have 6 new (well refurbished) injectors. It was idling really rough after that. I reset the computer.
I also just installed a new TPS and IAC, still a rough idle. Does the car just need to run awhile before it gets used to it?
 

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1988 Jeep Cherokee 4.0 6cyl
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Discussion Starter #7
The TPS sensor also looks crooked?
229131
 

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Is it just idle, or is it at all engine speeds?
 

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Discussion Starter #9
Pretty much all engine speeds. The only time it's not really doing it is when I let my foot off the gas and let the mph go down
 

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OK, then check for spark at each plug and check compression. Also make sure you are not getting exhaust gasses in your coolant. That can be done at a radiator shop
 

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Discussion Starter #11 (Edited)
Ok I have a multimeter but tomorrow I need to go buy some back probe pins.

This Jeep is killing me right now :(
 

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If you have a miss at all rpms, I don't think it is the TPS. That is why I think you need to search in a new direction. You could have a bad injector, but let's narrow it down to non mechanical and spark first
 
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1988 Jeep Cherokee 4.0 6cyl
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Discussion Starter #13
So I was low on funds and ordered some injectors from ebay.
I bought the 0280155746. So I went from 1 hole to the 4 hole.

I wouldn't have to upgrade the fuel rail or pressure regulator correct?

I'm hoping I didn't make a horrible mistake here by having these installed.

229132
 

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As long as it doesn't leak, you are OK
 

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1988 Jeep Cherokee 4.0 6cyl
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Discussion Starter #15
Ok I THINK I've found an issue. The mechanic may or may not have broken a piece of the MAP Sensor Vacuum Line.
I know on Cruisers site he has a way of tapping a new one in. But I don't have that. Anybody know where I could get a new line and possibly the rubber fitting that goes onto the throttle body?
 

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Not sure, but check with NAPA. They have access to OEM rubber
 

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Discussion Starter #17
Ok I've been trying to test the TPS sensor and I'm getting 0 on my multimeter. Wtf is going on here :(
 

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Check for 5V supply with key on
 

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Discussion Starter #19
So when I unplug the 3 pin sensor (I have an automatic so I have both), it's reading at like 4.72 or something. So I'm getting voltage from that. But when I clip them back together and back probe, I get nothing. The whole back probe thing scares me too because I don't want to accidentally pierce the wire.
 

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Sometimes you cannot get your probe into the back of the plug enough to contact voltage. There are times I use a sharp probe to pierce the insulation. However take it easy, you don't want to mangle it badly
 
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