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Doggy XJ (Renix Content)


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I've been spending my free time for the last year and a half on a labor of love that is a '90 XJ. The body on it is in great shape, the main reason why I am wasting my time on it. I bought it with a bad motor and have since swapped in a good motor from an '88 that I bought for parts. The '88 was wrecked, I was able to get the motor running very good before I pulled it from the rest of the smashed carcass. After having the motor on a stand, I was able to look it all over and it is in very good shape...

 

I've gotten everything back together in the '90 and have been driving it around the yard for the last month or so. It has been idling quite rough but I had attributed this to the vacuum lines not being hooked up. I hooked them all up yesterday and much to my disappointment it still has a rough idle. I made sure that the Throttle body and IAC were clean and this didn't help. I ran it down the road for a few miles and it just has no power to speak of. Its having a hard time getting to overdrive and I can only get it to go to 40-45 MPH top speed. I've played with the kickdown cable and it seems to have no effect. I've checked the sensors, especially the O2, and everything seems good there. The transmission is good, it is not slipping. After running it down the road and getting back to the garage, I could smell the un-burnt gas in the exhaust. I had the distributor out while I had the engine out. From what I know, the timing is either on or off, no adjustment, right?

 

I went all through this thing when it was apart, I'm sure that it is something that I forgot to hook-up but after checking it all over I can't find anything unplugged.

 

Even with everything I've done to my MJ's, I've never been here with a Renix before, Any thoughts on what to check?

 

Thanks in Advance!

 

'90 XJ Laredo - 4.0L/AW4/NP242

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timing could also be way far off. As in very retarded.

You have a timing light?

 

I can get one, yes.

 

I was really thinking that it might be something to do with timing but I've never heard of the timing as being something adjustable... I had the dizzy out when I cleaned the block off and a friend and I rotated the assembly to TDC on #1 and put it back in and it has been there ever since...

 

With the un-burnt fuel and lack of power, to me it acts like the timing is off. When I get on the throttle the thing backfires a bit, new exhaust pipe is already black on the inside from running rich for about 3 miles...

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If the distributor was off a tooth, I don't see how it's possible that it could get up to even 45 mph.

 

IIRC the dizzy has ten teeth. Being one off would put the dist 36 degrees off, and given that the rotating assembly goes twice as fast, that would put it 72 degrees off....

 

I had one where the timing chain was off a tooth, and that would cause only a 10 degree difference. It barely even idled, and would choke out when you gave it gas... unloaded.

 

Seeing that it's drivable up to that speed, I don't think it's the dizzy.

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IIRC there is a procedure involving using a cutaway cap to index the distributor. Bring the engine to tdc, put on your cutaway cap, (cutaway at no. 1), the rotor should just be touching no. 1. You could just be one tooth off. I was after replacing my engine. It ran, but badly. Moved the rotor back one tooth, problem solved. Hope this helps.

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Remove the distributor cap and cut a "window" into the side of the distributor cap at the #1 spark plug wire post . The "window" should be large enough to allow easy visual inspection of the position of the distributor rotor at the #1 spark plug wire post. Reinstall the distributor cap.

 

Install a ¾” wrench or socket onto the vibration damper retaining bolt. Rotate the engine in a clockwise direction until the #1 cylinder is at top dead center. Align the timing mark on the vibration damper with the "0" degree mark on the front cover timing scale. The tip of the distributor rotor should be near the #1 spark plug wire post.

 

Disconnect the distributor electrical connection. Remove the distributor holddown clamp, holddown bolt and distributor. Remove the distributor cap and rotor.

 

Place the distributor housing upside down in a soft jaw vise. Scribe a line 1/2 inch from the end of the distributor locating tab. Cut the distributor locating tab at the scribed line with a saw.

 

Remove any burrs and metal filings from the distributor. Reinstall rotor.

 

If necessary, using a flat blade screwdriver, turn the oil pump gear drive shaft until the slot is slightly past the 11 o'clock position. The oil pump gear drive shaft is accessible through the distributor mounting bore in the engine block.

 

Visually align the modified locating tab area of the distributor housing with the holddown clamp bolt hole.

 

Turn the rotor to the 4 o'clock position.

Lower the distributor into the engine block until it seats. The rotor should now be very close to the 5 o'clock position.

 

Reinstall the distributor cap with the cutout "window". Rotate the distributor housing until the trailing edge of the distributor rotor tip is just departing from the #1 spark plug wire post terminal .

 

Reinstall the distributor holddown clamp and bolt.. Reinspect the position of the rotor to the #1 spark plug wire post to insure that it has not moved.

 

Install the new distributor cap, reconnect the distributor electrical connections.

 

Revised 07/03/2012

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Thanks for the tips on the cut-away distributor cap. I have some extras around that will work great to hack up and try this with.

 

Gotta ask. Did you get the 3 small ground wires connected to the engine dipstick tube stud which was clean and shiny when you did the engine swap?

 

Yes. The entire engine bay and harness were cleaned when the motor was out. Di-electric grease was used when these wires were bolted back down to the block with the NEW 2 gauge battery cables.

 

ck vac line fr TB to MAP for leaks. Fuel filter maybe plugging up.

 

Yep, this is vac line is all hooked up. New WIX fuel filter was installed when I installed the new gas tank.

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When the time comes to adjust the tPS, use these instructions:

 

 

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 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. 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 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 08-27-2012

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Thanks for all the info everyone. I wanted to let you know that I won't be able to work on this for the rest of the week. It'll probably be the weekend after Labor Day before I get back to messing with it. I will update again then.

 

Thanks Again - Brent

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  • 2 weeks later...

So this is what I found with the cut-away cap test... #1 cylinder is at (or slightly beyond) TDC. I watched the piston rise with a flashlight and turned the crank just beyond the stopping point for the piston's rise.

 

418926_781759071457_1129169331_n.jpg

 

579915_781759086427_930585644_n.jpg

 

I only had time to play with this last night, I have not tried anything else... I will have lots of time on Saturday to mess with this.

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I did not check the vibration dampner to see the notch at 0. Everything is as I left it last night, I can check it tonight to see where it is.

 

Good idea. Cut the rest of the dizzy cap away so #1 terminal can be seen better and take another photo. I wanna steal it from you.

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So its raining, tomorrows plans become today's. I've got the rest of the night to mess with this...

 

I verified that #1 cylinder is at TDC by checking the timing mark on the vibration dampener.

 

296885_781900752527_213776666_n.jpg

 

Next put the cut-away cap back on (2 shots for cruiser54 - use these shots all you want!).

 

561618_781900897237_2130846302_n.jpg

548059_781898791457_86530979_n.jpg

 

I re-clocked the distributor to this setting (right most yellow paint) and it would not start. So it all came back apart and reset to the original setting (left most yellow paint) and things came back to where they were, running, but kind of rough...

 

558429_781901106817_275814794_n.jpg

 

So in my opinion, timing has been ruled out as OK.

 

I started with your procedure for checking the TPS and in the first step I found that I have 9.1 ohms of resistance in the engine bay harness. I think we are onto something here, do you have that procedure for repairing the harness?

 

 

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.

 

Also, I cleaned the Throttle Body in my earlier attempts to troubleshoot this problem. Nice and shiny and carbon free inside and out...

 

Thanks in advance - Brent

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Couple of questions Brent:

 

In the below photo, how many teeth did it take to set the rotor from the right yellow mark to the left yellow mark? 1? 2?

558429_781901106817_275814794_n.jpg

 

In this photo have you tried a timing light and watched the balancer vs. crank pulley marks? They should be nice and steady and advance smoothly as you rev up the engine. If it's jumping all around, causes include worn distributor shaft bearings causing side-to-side play and/or timing chain wear/slop, both of which can cause rough idling.

296885_781900752527_213776666_n.jpg

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Sensor ground circuit resistance is too high. Here's what you need to do about that:

 

Find your Intake Air Temp sensor. It's the sensor just to the rear of the throttle body, has 2 wires, and screws into the intake manifold.

Where it's connector plugs into the harness you will see that one of the wires on the harness side is brown with a white stripe. Follow the brown with white stripe wire back into the harness. You'll have to open up the split-loom plastic sheathing to follow it. It will come to a splice with 2 other brown with white wires with duct tape over them. They're from the TPS and the CTS. The 3 wires will be spliced to a single wire headed toward the C101 connector if you have an 87 or 88. If you have an 89 or 90, you do not have the C101 bulkhead connector.

 

Now go to the MAP sensor. Follow the brown with white wire into the harness from there. You will find a splice with 2 more brown with white wires with duct tape over them. At the splice you will find the 3 wires connected to a single brown with white wire going toward the C101, or just along the firewall towards the engine if you have an 89 or 90. Along with the MAP sensor that you traced, they are the ECU sensor ground port and the diagnostic connector on the passenger inner fender.

 

You now have 2 sets of 3 brown with white wires, one near the firewall and one near the engine.

 

Cut the splices out of each set of wires eliminating not only the crappy factory splices, but also the single wire between them. Bring both sets of 3 wires together. Solder the 2 sets of wires together and insulate them properly with tape or shrink tubing.

 

Zip-tie up your new sensor loom to allow for engine movement. I prefer to cover it with some new split-loom or wrap it neatly with electrical tape when done.

 

 

 

Revised 03-09-12

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