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  #1  
Old November 29th, 2012, 06:28
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high idle caused my dash lights/tail lights to go out??

Hi again, folks. Welcome to this week's meeting of the XJ High Idle Club. It's been merely hours it seems since we last all met.

Started the 88 XJ yesterday am. Immediate 3000 RPM idle. Off & on 8-10 times did nothing. Left for work. Nothing like standing on the brake, BARELY (and I mean barely) being able to hold it back from hitting the guy in front of you crawling on the freeway (SoCal). If I got an open spot and could take my foot off the brake, it went nearly 55 MPH on it's own. Never touched the gas all the way there. Good times. Fought it for 30+ miles. End of day, crossed my fingers, and...no change. Fought it home 28 miles in the rain. Holding it back in the rain is a whole 'nother experience with the lack of good traction. It never came down from 3k all damn day. The brakes were straining and moaning, my right foot was aching from raising it 1/16" off the pedal, then pushing it thru the floor all day.

2 miles from home, on it's own, the RPMs dropped and it drove normally. This damn SOB. I pulled over, cut it off and on, and it was "fixed." However, I had no dash lights or rear tail lights. Checked all fuses, all good.

What fuse circuit are these lights on/which fuse? Any other ideas to try to get me my tail lights back? I need to try and fix it today @ lunch so I can drive it home tonight in the dark. Of course, if you have ideas to fix the high idle other than a bullet thru the block (and it may come to that) I'm all ears on that too.

I'm to the point with the high idle that I'm about to take it to the Jeep dealer and say "fix this SOB". I know it ain't gonna be cheap (if there is even a true fix) but I'm tired of it. So GD tired of it.
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Old November 29th, 2012, 07:18
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Re: high idle caused my dash lights/tail lights to go out??

Search for "Cruiser54" Renix fixes, and for Ecomike's "RenX files". Start with cleaning the battery and engine block ground contacts (near the oil dip stick. passanger side and the rear block top, driver's side, do both sides, get them to bare metal. Then do the Renix sensor ground wiring harness fix, then test the TPS and its ground.
And stop driving it until the idle is fixed. Way too dangerous and real bad for the transmission!!!
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Old November 29th, 2012, 07:50
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Re: high idle caused my dash lights/tail lights to go out??

the parking lamps are the blue wires.

Start checking fusible links after you check all the grounds. Don't forget the one in the back.
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Old November 29th, 2012, 09:33
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Re: high idle caused my dash lights/tail lights to go out??

Thanks Mike. BTW, what kinda potential tranny damage are we talking about? And do you know if those fixes are actual fixes that WORK, or are they "short time solutions"?

Fusible links? The only one I know if is the one near the block that you blow when you let an idiot @ Sears hook a new battery up for you. Are there others? Location?

The one in the back....this the one under the cargo door cover...blue wire & bullet connectors? I guess they COULD have touched, maybe? Anyone else find it odd that as soon as the high idle stopped, the dash/tail lights went out? I would have thought the fuse would have blown....
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Old November 29th, 2012, 10:10
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Re: high idle caused my dash lights/tail lights to go out??

They are the only fixes that WORK. Written by two 87-90 Renix era Jeep experts, Me and Cruiser54.

Possible Tranny damage, killing the torque converter, overheating the transmission, burning the T-fluid up, burning out the clutches, and driving into an irresistable object Crash BOOM Bang!

"Anyone else find it odd that as soon as the high idle stopped, the dash/tail lights went out? "

Not at all. Both sound like and point to one or more loose dirty grounds which is all too COMMON on the 87-90 Renix jeep!!!

Quote:
Originally Posted by wgregt View Post
Thanks Mike. BTW, what kinda potential tranny damage are we talking about? And do you know if those fixes are actual fixes that WORK, or are they "short time solutions"?

Fusible links? The only one I know if is the one near the block that you blow when you let an idiot @ Sears hook a new battery up for you. Are there others? Location?

The one in the back....this the one under the cargo door cover...blue wire & bullet connectors? I guess they COULD have touched, maybe? Anyone else find it odd that as soon as the high idle stopped, the dash/tail lights went out? I would have thought the fuse would have blown....
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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Old November 29th, 2012, 10:13
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Re: high idle caused my dash lights/tail lights to go out??

http://www.naxja.org/forum/showthrea...=cruiser54+fix

http://www.naxja.org/forum/showthrea...ght=Renx+files
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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Old November 29th, 2012, 10:35
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Re: high idle caused my dash lights/tail lights to go out??

It sure enough could be a ground issue. If not a ground issue, probably the tail light fuse is blown. Just because it looks good doesn't mean it is good, you really have to volt test both sides of the fuse to be sure and even then they sometimes have a wiggle failure that is intermittent.. The circuit for the dash lights goes through the tail light fuse, up to the rheostat (dimmer) back down to the instrument fuse and back up to the dash lights. I've seen shorted rheostats (in the headlight switch) or a cut cable where the cable bundle follows the seam above the fuse block (to the left).
Could be a short in the taillight harness, bulb or where ever, anything that pops the tail light fuse will also kill the dash light power (even if the instrument light fuse is good).

High idle, 3000 RPM, most likely a TPS issue. I've done my TPS in a few times washing my motor or running through a mud puddle. They get full of water and can run your idle up high or simply fail outright.

Possible it is a major vacuum leak, most likely a large vacuum line, like the brake booster or the main line running to the vacuum canister. The smaller vacuum lines won't run the idle up that high.

If the fusible link goes you loose all the headlights, depending on which link, it is a multiple system failure, not just one or two items. The fusible links are like the main fuses in your house, one goes out and a whole floor is dark. Regular fuses are for one room or lights or outlets etc.

Last edited by 8Mud; November 29th, 2012 at 10:41.
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Old November 29th, 2012, 12:35
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Re: high idle caused my dash lights/tail lights to go out??

It could also be explained by a bad ground (like I said) and the head light switch (or its wiring at the switch) going bad, and then the drop in amps going through the ground wire (due to failed head light switch) lowered the voltage on the bad ground wire at the TPS, and thus lowered the idle!!!!

Seen that myself too many times!!! The head light switch and wiring is way under sized!!!!
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #9  
Old November 30th, 2012, 04:38
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Re: high idle caused my dash lights/tail lights to go out??

I'm pretty darn sure the 2 problems aren't related. Your TPS is dying on you. You can check the sensor ground circuit as described in the following write-up, but I'm gonna say your TPS is toast. You're gonna end up replacing and adjusting the new one.

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
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Old November 30th, 2012, 06:57
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Re: high idle caused my dash lights/tail lights to go out??

Checking around online, and the TPS new is really less than $20?? I thought for some reason it was waaaaay more...like several hundred.
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Old November 30th, 2012, 12:45
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Re: high idle caused my dash lights/tail lights to go out??

A good TPS costs more like $45.
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Old November 30th, 2012, 22:40
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Re: high idle caused my dash lights/tail lights to go out??

I checked all the fuses again with new ones.Took the hatch cover off, and the blue wires were not touching (taped them up anyhow.) Found nothing that would keep the tail lights off yet.

Any other ideas on what to check to get these tail lights workin' again?

If it's the headlight dash rheostat, is there any way to check it? Would it require a new headlight switch, or is the rheostat/dimmer separate from that pull-out headlight switch? Any way to bypass it and see if it's the problem? Dealer-only item?

Just throwing out ideas here....

And to get to that switch, I assume the dash panel/radio has to come out, and it's accessible then?

Last edited by wgregt; November 30th, 2012 at 22:44.
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Old December 1st, 2012, 03:15
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Re: high idle caused my dash lights/tail lights to go out??

Were any fuses blown?

Rheostat is part of the switch.

Headlight switch can be removed without taking the dash apart. It's still a PITA.
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Old December 1st, 2012, 06:10
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Re: high idle caused my dash lights/tail lights to go out??

headlamp switch can be removed by taking the lower dash kick panel off, you can see it from underneath. The hardest bit will be getting to the release button that releases the knob and rod from the switch. You need tiny hands. Takes about an hour of being upside down under the dash.
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Old December 1st, 2012, 07:37
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Re: high idle caused my dash lights/tail lights to go out??

Quote:
Originally Posted by cruiser54 View Post
Were any fuses blown?

Rheostat is part of the switch.

Headlight switch can be removed without taking the dash apart. It's still a PITA.
No blown fuses. Wish there had been.
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