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88 Cherokee will not idle

2K views 41 replies 3 participants last post by  miceanic 
#1 ·
As the title states, also VERY hard to start, have to pump gas to started and keep running. I cannot hold it, i have to pump it. While it is cold if i let rpms get low sounding it bogs out or if they get high it bogs out. But once warm it will run just not idle with out pumping it.
 
#3 ·
I have cleaned the throttle body and replaced vacuum lines, i have to go buy more line thought. That line looks good, after i cleaned it with parts cleaner it ran better but had a surging idle. Replacing a few lines fixed that. But it tries to correct idle but does die.
 
#4 ·
No bolts are missing but there us a hole above the map sensor line on the intake, it had nothing in it so i plugged it. I think i still have a leak and will keep looking for it, but have traced all lines with a vacuum diagram and not found it. Could i just eliminate that vacuum tree thing and run the lines directly to their connection?
 
#9 ·
Starter rebuilt, it works fine i replaced it same, so i got my money back. I did a ground refresh as i read that might help. Battery is new. I cleaned all connections i could find as stated in the ground refresh thread i read. I will be getting new cables as these are 25 years old.
 
#11 ·
Now, about that hole i plugged is it supposed to be plugged? I read a thread on the IAC, pulled it and i could hardly get it out. It was frozen in with carbon build up. But in the diagram that explained how it worked, it showed an air passage, and that hole at the end of it.
 
#14 ·
Plastic plug from an old refrigeration unit.
It in the pic but without plug.
Replaced battery cables, put two new negatives for extra ground, and still starter clicking. Could it not be getting a charge to turn? As in a relay engaging the solenoid for the gear to move to the flywheel, but not for the motor to turn, if that makes sense.
 

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#16 ·
I would suggest having someone jump start it. If it clicks before you hook it up and it doesn't click after then you know your battery doesn't have the juice needed to turn over our you can use a multimeter if you dont have an extra vehicle laying around to see how much charge it is holding.
 
#20 ·
Renix Tips
I just noticed your Renix Refresh tips, i am going out right now and do #18 For my under dash ground. I love that thread. I will slowly be doing all of them, that is GREAT advice, thanks for taking the time for doing that. It is going to help me work the bugs out of this.
 
#18 ·
It does it if its jumped too, i tapped the starter relay and it starts, i guess that is the problem. It started acting up so i cleaned the contacts on it and it works, i ordered a new relay. I also am now tracing wires so i can fix my electrical issues. When i tried to test the tps though, it says i need a square connector with 4 wires to test the engine not to use the flat connector, my tps square connector only has 3 wires.
Would a bad map sensor cause misfiring at low idle, high rpm ,and hard starting ,and throttle issues, as in i only can get it to run if i pump it?
 
#21 ·
Well i just realized, if it is cold the starter does not give trouble, once its warm it will not work.
I just ordered new TPS, IAC, MAP, Wires, Starter, Plugs. I will see if that helps, and will replace rotor and cap when i can.
Also is the timing adjustable on this, my father asked me because it sounds like the timing is off because of the hard starts, and once it runs it starts spitting through the intake and kicking back and misfiring bad.
 
#25 ·
Adjust it using the flat connector as if it were a manual transmission vehicle.


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
 
#26 ·
Now its adjusted, no surging idle thanks. My dad just looked at it, and he said its fuel delivery problem, guess i will pick up pressure tester tomorrow and prob. will have to drop the tank and clean the filter on the fuel pump, because the other filter is new, and most lines are new outside the tank.
 
#28 ·
He can't too much, he broke his neck in a few places, a few years back, and that is why i got into automotive he could no longer do it, i love it, my first was 92 cherokee and it needed a motor in it. He gives advice if i cannot figure it out. I love working on vehicles, especially JEEPS.
This twitchy Renix is kicking my butt though. But it will always leave me with something to do after school. And when i am bored.
 
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