Mystery Nipple

[caseyrstewart]

Does anyone know what the nipple in the attached picture does (located directly across from the TPS sensor)? I noticed today that nothing is attached to it. Coincidentally, there's a hose nearby not attached to anything. I almost connected the two, but figured I should ask the group first. Thanks!

 

https://www.dropbox.com/s/zp54l0jdfmonm0r/Photo%20Feb%2027%2C%201%2058%2003%20PM.jpg?dl=0

 

 

[onlyinajeep726]

 

It's a port for vacuum off of your intake manifold.  As to what connects to it, I'm not 100%.  But that big hose doesn't connect to that.

 

What year is your MJ, Renix era?

 

*EDIT: I realize it's a Renix era upon closer inspection of your pic...

That nipple goes to the CCV breather on the back of the valve cover, seen below:

 

[cruiser54]

[caseyrstewart]

Great! Thanks for your replies. I can always count on comanche club for useful information. 

 

In other news, I'm having a hell of a time figuring out why my truck is sputtering. Pretty certain it's a combustion issue, but as to what is causing it, I don't know. The issue came out of nowhere. At first I thought I was out of gas, but quickly realized it was a bigger problem. Thus far, I've looked at the TPS sensor, check my spark plugs, changed the air filter, replaced a couple vacuum hoses, verified the fuel filter is not too old (I bought this truck about a year ago), cleaned the throttle body, and checked fuel pressure (around 30 psi). I thought I had fixed it after cleaning the throttle body. It was pretty gummed up and for about an hour after it was cleaned out, the truck drove great. Then all of a sudden, it chugged to a stop on the highway and I had to get it towed home. Scratching my head now as to what project I should tackle next...

[cruiser54]

Fuel pressure should be 31 with the vacuum line connected to the fuel pressure regulator and 39 when disconnected. 

 

Have you ever tested your CPS?

 

What year MJ?

[caseyrstewart]

I have not tested the CPS yet. It's an 87.

[cruiser54]

I have not tested the CPS yet. It's an 87.

You could still have a fuel pressure issue and/or an electrical issue.

 

How's the vacuum line from the throttle body to MAP sensor?

 

I would test the CPS. Tip 7. 

 

Have you performed any of my Renix Tips at all? 

[1stDeuce]

If that nipple is still open, that's a pretty good vacuum leak.  That would possibly give you a lean stumble at idle...  You need to at least cap it if you don't have the connector hose.

[caseyrstewart]

 

I have not tested the CPS yet. It's an 87.

You could still have a fuel pressure issue and/or an electrical issue.

 

How's the vacuum line from the throttle body to MAP sensor?

 

I would test the CPS. Tip 7. 

 

Have you performed any of my Renix Tips at all? 

 

 

 

I've attached a right angle connector to the "mystery nipple" and believe all is well there. Vacuum line to the MAP sensor is connected and looks ok. I plan to go through your entire set of renix tips this weekend when I get some time.

 

Can I ask a stupid question? How does everyone post photos on this forum?

[cruiser54]

 

 

I have not tested the CPS yet. It's an 87.

You could still have a fuel pressure issue and/or an electrical issue.

 

How's the vacuum line from the throttle body to MAP sensor?

 

I would test the CPS. Tip 7. 

 

Have you performed any of my Renix Tips at all? 

 

 

 

I've attached a right angle connector to the "mystery nipple" and believe all is well there. Vacuum line to the MAP sensor is connected and looks ok. I plan to go through your entire set of renix tips this weekend when I get some time.

 

Can I ask a stupid question? How does everyone post photos on this forum?

 

Not a stupid question about photos. Took me forever to do it. 

 

You bring them in from another site like photobucket etc. 

[caseyrstewart]

So I've taken some time to go through the Jeep's combustion system. Got sidetracked by an oil pan/RMS project. Either way, it all has to get done at some point...

 

Beginning to think it's a problem somewhere in the vacuum system. I went to Auto Zone and picked up both a fuel pressure tester and a vacuum pressure tester. Fuel checked out perfectly. 31 with the vacuum line connected and 39 with it disconnected.

 

When I checked the vacuum system, I connected a gauge to the nipple facing straight up on the intake manifold (not the one that goes to the CCV breather) and read between 15 and 20. The needle was moving quite a bit. According to this youtube video, I think I would fall under catagory 3 (plug gap, dwell, coil distributor cap, or plug wires). However, I know the distributor and plug wires are in good shape as they've been replace recently.

 

Anyone have thoughts on what I should tackle next? To be fair, the truck is driving smoother now. The EGR is completely bypassed at the moment and the truck only seems to sputter or die occasionally. I can drive it around the block and usually only have problems when I'm going up or down a hill.

[cruiser54]

So I've taken some time to go through the Jeep's combustion system. Got sidetracked by an oil pan/RMS project. Either way, it all has to get done at some point...

 

Beginning to think it's a problem somewhere in the vacuum system. I went to Auto Zone and picked up both a fuel pressure tester and a vacuum pressure tester. Fuel checked out perfectly. 31 with the vacuum line connected and 39 with it disconnected.

 

When I checked the vacuum system, I connected a gauge to the nipple facing straight up on the intake manifold (not the one that goes to the CCV breather) and read between 15 and 20. The needle was moving quite a bit. According to this youtube video, I think I would fall under catagory 3 (plug gap, dwell, coil distributor cap, or plug wires). However, I know the distributor and plug wires are in good shape as they've been replace recently.

 

Anyone have thoughts on what I should tackle next? To be fair, the truck is driving smoother now. The EGR is completely bypassed at the moment and the truck only seems to sputter or die occasionally. I can drive it around the block and usually only have problems when I'm going up or down a hill.

Check the distributor indexing. Tip 13. 

[caseyrstewart]

 

So I've taken some time to go through the Jeep's combustion system. Got sidetracked by an oil pan/RMS project. Either way, it all has to get done at some point...

 

Beginning to think it's a problem somewhere in the vacuum system. I went to Auto Zone and picked up both a fuel pressure tester and a vacuum pressure tester. Fuel checked out perfectly. 31 with the vacuum line connected and 39 with it disconnected.

 

When I checked the vacuum system, I connected a gauge to the nipple facing straight up on the intake manifold (not the one that goes to the CCV breather) and read between 15 and 20. The needle was moving quite a bit. According to this youtube video, I think I would fall under catagory 3 (plug gap, dwell, coil distributor cap, or plug wires). However, I know the distributor and plug wires are in good shape as they've been replace recently.

 

Anyone have thoughts on what I should tackle next? To be fair, the truck is driving smoother now. The EGR is completely bypassed at the moment and the truck only seems to sputter or die occasionally. I can drive it around the block and usually only have problems when I'm going up or down a hill.

Check the distributor indexing. Tip 13. 

 

I've installed and indexed a new distributor. The old one was leaking oil into the bottom of the cap below the rotor. Bypassed the C101 and refreshed grounds according to step 27. 

 

While underneath today I noticed what appears to be a ground cable dangling near my CPS (which I also just replaced). Looks important. Should this be connected to something?

 

[caseyrstewart]

Oh, right. I also can't get it to start at all now that I've replaced the CPS. At least before I could drive it, just not well. Help! I'm worse off than when I started!

[caseyrstewart]

Oh, right. I also can't get it to start at all now that I've replaced the CPS. At least before I could drive it, just not well. Help! I'm worse off than when I started!

 

 

All is well! After countless hours of working on this issue, a simple bolt into the block of the engine attaching the ground strap pictured above and BOOM! Truck is running like a dream. I have no idea why anyone would have ever removed it and will never know. Just glad my Jeep is running again. Thank to all who helped along the way.

[cruiser54]

 

Oh, right. I also can't get it to start at all now that I've replaced the CPS. At least before I could drive it, just not well. Help! I'm worse off than when I started!

 

 

All is well! After countless hours of working on this issue, a simple bolt into the block of the engine attaching the ground strap pictured above and BOOM! Truck is running like a dream. I have no idea why anyone would have ever removed it and will never know. Just glad my Jeep is running again. Thank to all who helped along the way.

 

Wow!! Tip #1 had it for ya. Glad you got it fixed!!

[HOrnbrod]

I can't believe that ratty cable was (and still is?) the sole source for your engine ground. Is this typical Renix? At a minimum I'd replace that mesh cable with at least a 6AWG copper cable with properly sized crimped/soldered brass terminals, plus a couple more engine ground cables to the front clip and the fender wells. With all the Renix sensors depending on a couple of ohms to work, you need a real solid engine ground plane installed.

[caseyrstewart]

I can't believe that ratty cable was (and still is?) the sole source for your engine ground. Is this typical Renix? At a minimum I'd replace that mesh cable with at least a 6AWG copper cable with properly sized crimped/soldered brass terminals, plus a couple more engine ground cables to the front clip and the fender wells. With all the Renix sensors depending on a couple of ohms to work, you need a real solid engine ground plane installed.

Might be hard to believe, but after installing it, all my symptoms went away. Drove around the neighborhood for 20 minutes trying to reproduce the issue and could not create a single hiccup. I'll look into beefing up the ground at some point. For now, I've got 3 weeks of truck errands to do.

[cruiser54]

I can't believe that ratty cable was (and still is?) the sole source for your engine ground. Is this typical Renix? At a minimum I'd replace that mesh cable with at least a 6AWG copper cable with properly sized crimped/soldered brass terminals, plus a couple more engine ground cables to the front clip and the fender wells. With all the Renix sensors depending on a couple of ohms to work, you need a real solid engine ground plane installed.

There's a ground from the battery to the block but that's it. Block to a bunch of sensors.

 

That's why I wrote Tip 1. Part numbers included for readily available upgraded and additional cables from Napa. If guys would just do that tip thoroughly right off the bat, they would have way fewer problems down the road.

 

Renix Ground Refreshing

 

The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.

 

 The components grounding at the dipstick tube stud are:

 

Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal.  All extremely important stuff.

 

The factory was aware of the issues with this ground point and addressed it by suggesting the following:

 

Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.

 

Inspect the wire terminals.  Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.

 

While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely. 

 

Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.

 

 First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.

Remove the other end of the cable from the rear of the head using a 3’4” socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.

 

A suggestion regarding the braided cable:

I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18” long with a 3/8” lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.

 

A further improvement to the grounding system can be made using a #4 cable, about 10” long with 3/8” terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.

 

For those of us with Comanches, it’s very important to remove the driver’s side taillamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Reattach securely.

 

If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com.  He makes an incredible cable upgrade for a very reasonable price.

 

 

Revised 03-04-2013

[HOrnbrod]

 

I can't believe that ratty cable was (and still is?) the sole source

 

If you want to upgrade your grounds and battery cables in general, contact Jon at   http://www.kelleyswip.com.  He makes an incredible cable upgrade for a very reasonable price.

 

Seconded.  And thirded............

[Whiz]

I just this week ordered my cables from Jon!  Sorry to jump in this thread but In relation to tip 1 I have a question. It appears that my Negative Battery Ground and all the other grounds are on the dip stick stud  together and not separate as mentioned in tip 1. I have looked and looked, I can not see anything else. When I change cables should I separate them?