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  #46  
Old February 3rd, 2012, 06:52
Shorty Shorty is offline
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

Quote:
Originally Posted by Crashsector View Post
Hooked the scanner up before I came to work to check the non-running reading on the IAT. It read 9 degrees C, along with the coolant temp sensor, which is exactly what the outside temperature was. So the good news is it looks like IAT sensor probably isn't borked.

Not looking forward to getting two 20 year old Torx bolts off

--Andy
what model scanner are you using to get temps. from the IAC and CTS? I know to get a OHM reading from them, but haven't seen a specific value chart associated with themp.
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  #47  
Old February 3rd, 2012, 08:56
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

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Originally Posted by Shorty View Post
what model scanner are you using to get temps. from the IAC and CTS? I know to get a OHM reading from them, but haven't seen a specific value chart associated with themp.
IIRC he has the OEM/ Chrylser ORB-II (?) test rig that works with Renix 87-90, a rare item these days.

Are you asking for an Ohm to temp conversion chart for Renix?
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  #48  
Old February 3rd, 2012, 09:41
Shorty Shorty is offline
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

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Originally Posted by Ecomike View Post
IIRC he has the OEM/ Chrylser ORB-II (?) test rig that works with Renix 87-90, a rare item these days.

I want one!!!!!

Are you asking for an Ohm to temp conversion chart for Renix?
yes, if it's better than the typical one with about 6-7 values that is usually posted-- I'd love one that can narrow it down to a couple degree range
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  #49  
Old February 3rd, 2012, 10:50
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

The scanners are easily had on eBay. That's where I got mine. It's a snap-on mt2500. Don't forget to make sure it has the right cartridges for the jeep. They are still available too pretty easily on eBay.
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  #50  
Old February 3rd, 2012, 10:57
Crashsector Crashsector is offline
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

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Originally Posted by magimerlin View Post
snap-on mt2500
This. Cost a pretty penny back in its day.



--Andy
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  #51  
Old February 4th, 2012, 04:30
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

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Originally Posted by magimerlin View Post
The scanners are easily had on eBay. That's where I got mine. It's a snap-on mt2500. Don't forget to make sure it has the right cartridges for the jeep. They are still available too pretty easily on eBay.
Called "The Brick".
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  #52  
Old February 4th, 2012, 09:18
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

If you just plug in the discrete data values into an excel spread sheet, and then tell excel to plot the data, continuous, you can get a nice print out of a continuous plot.
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  #53  
Old February 4th, 2012, 17:23
Shorty Shorty is offline
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

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Originally Posted by Ecomike View Post
If you just plug in the discrete data values into an excel spread sheet, and then tell excel to plot the data, continuous, you can get a nice print out of a continuous plot.
wasn't sure if it was linear or not-- always theorized an average temp that way
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  #54  
Old February 4th, 2012, 21:55
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

No it is not linear. But Excel will draw a connect the dots plot. There are also curve fitting tools in Excel!!!!
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  #55  
Old February 5th, 2012, 09:27
Crashsector Crashsector is offline
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

EGR Valve.

Final answer.

What a weight off my shoulders. Replaced the EGR valve and started taking the new plugs out one by one to inspect. Plug #1 cracked when I was trying to tighten it back in. Either that was causing the misfiring, or the entire engine was so heatsoaked when I was last testing that it was just detonating on every pulse.

Started it up and it smoothed out to a nice idle around 1kRPM in open loop. After about 30 seconds it went down to about 750RPM and fell right in to closed loop. Drove it around for about 20 minutes and it feels tip top. Scanner says the EGR is open at highway speed under throttle and it closes when it's not. Intake temps are around 60C, which is about 140F which sounds right. O2 is flipping between lean and rich constantly and coolant temp is in the green. Vacuum at idle is a stable 17 inches.

Ignorant comment: Holy crap this engine has some torque! This is my first Jeep, and I knew the potential, but wow. It's not going to get anywhere fast, but nothing can stop it.

I feel so much better now. Time to move on to the rear bumper and hitch project...

--Andy
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  #56  
Old February 5th, 2012, 09:56
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

I wonder how that scanner knows if the EGR is actually open? I doubt it actually knows that sense there is no direct sensor on the EGR. It must be interpolating intake air temp changes and or O2 sensor data and fuel trim data when it instructs the EGR solenoid to apply vacuum to the EGR to open it, and if it sees the right response it assumes the EGR is working.

Congrats on the fix.
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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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  #57  
Old February 5th, 2012, 10:51
Crashsector Crashsector is offline
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

Quote:
Originally Posted by Ecomike View Post
I wonder how that scanner knows if the EGR is actually open? I doubt it actually knows that sense there is no direct sensor on the EGR. It must be interpolating intake air temp changes and or O2 sensor data and fuel trim data when it instructs the EGR solenoid to apply vacuum to the EGR to open it, and if it sees the right response it assumes the EGR is working.

Congrats on the fix.
The computer controls the EGR Solenoid (driver side fender inside engine bay). It only opens when the engine is up to temp (by opening the solenoid and allowing vacuum to pull the diaphragm out on the valve), you're at highway speed, under throttle and under load. It adjusts the fueling to account for the extra "air". The idea is to lower combustion temps to reduce emissions. The computer doesn't actually know for sure if it's open or not, hence my problems. I assume newer fuel injection systems do exactly what you said to figure out if it really is open or not and triggers the appropriate trouble code.

The spring action in mine was toast so the exhaust pressure was keeping it open even though the computer hadn't opened it, so it was really screwing with my air/fuel.

Got the junkyard wiper transmission in too so it's pretty drivable. Doesn't look great without a bumper, but what are you gonna do.

--Andy
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  #58  
Old July 12th, 2019, 13:32
randy57 randy57 is offline
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

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Originally Posted by cruiser54 View Post
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.
The automatic TPS four-wire connector A,B,C, and D, how do you back probe and test D when there is no wire connected to D?
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  #59  
Old July 12th, 2019, 13:44
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cruiser54 cruiser54 is offline
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

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Originally Posted by randy57 View Post
The automatic TPS four-wire connector A,B,C, and D, how do you back probe and test D when there is no wire connected to D?
Is there a wire at C?

Anyway, are you dealing with an engine or a trans issue?

If engine issue, ignore the trans connector.
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  #60  
Old March 6th, 2020, 21:25
pyrohildy pyrohildy is offline
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Re: Guess what? I have a RENIX XJ with a rough idle and misfires!

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Originally Posted by cruiser54 View Post
Always adjust your TPS on the "engine side" per the following instructions when chasing a driveability problem. The trans side of the TPS (which you've been using to adjust) is separate from the "engine side" which is where the problem may very well be.
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.
Revised 11-28-2011



Does this stuff change between the 2.5 and the 4.0? Or TBI vs multiple injectors?
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