shorten throttle cable

[MDJEEPER]

Guys,

I need to shorten my throttle cable so the carb hits WOT before the pedal hits the floor. What's the easiest way to do this?

It's the stock BBD carb set-up, so I am guessing that the cable has stretched over the years.

Thanks!

 

[CJ]

Just trim the outer casing, and the inner cable. But I have never seem a cable housing stretch?

 

[MDJEEPER]

Thanks! I am a little confused though, as I already have some bare cable running between the firewall and the gas pedal...

It's almost like I need to cut the exisitng cable stop off, cut the bare cable, and then put a new cable stop on...but what to use for a new cable stop??

Is it possible that the PO put the linkage at the carb/exhaust manifold in the wrong position? It doesn't appear as though there is any way for it to rotate...

 

[TDHofstetter]

Well, THAT doesn't sound right! When the motor flexes under load, the throttle will do funny things!

Can ya pop us a picture of that animal? I'm thinkin' you're gonna' want to put a complete throttle cable in it, with a sheath & everything.

 

[mylittlecj5]

Thanks! I am a little confused though, as I already have some bare cable running between the firewall and the gas pedal...

It's almost like I need to cut the exisitng cable stop off, cut the bare cable, and then put a new cable stop on...but what to use for a new cable stop??

Is it possible that the PO put the linkage at the carb/exhaust manifold in the wrong position? It doesn't appear as though there is any way for it to rotate...

If you end up doing this, most auto parts stores will sell a package of universal cable stops to ya. I have one of them on my throttle cable.

 

[MDJEEPER]

Well, THAT doesn't sound right! When the motor flexes under load, the throttle will do funny things!

Can ya pop us a picture of that animal? I'm thinkin' you're gonna' want to put a complete throttle cable in it, with a sheath & everything.

Your wish is my command!

It was a little difficult to get a good picture of the linkage itself with the steering column and various hoses in the way. The internal picture shows the amount of slack in the cable.

 

[TDHofstetter]

Ok, I feel better now - it's sheathed.

First picture - the snap-on linkage attached to the throttle bellcrank. Follow it up, it ducks inside the sheath in the fourth picture. That sheath is attached to a bracket (still fourth picture) a fixed distance away from the throttle bellcrank. Move (bend?) that bracket farther away from the bellcrank and it'll take up more of the slack at the gas pedal (second picture).

 

[MDJEEPER]

Ok, I feel better now - it's sheathed.

First picture - the snap-on linkage attached to the throttle bellcrank. Follow it up, it ducks inside the sheath in the fourth picture. That sheath is attached to a bracket (still fourth picture) a fixed distance away from the throttle bellcrank. Move (bend?) that bracket farther away from the bellcrank and it'll take up more of the slack at the gas pedal (second picture).

Thanks! Great idea! I now have WOT.

Unfortunately, my jeep still cannot maintain 60 MPH in 4th gear when climbing any sort of incline...even very modest slopes...even now at WOT. The timing is right on, checked the vacuum advance (it's working), and have replaced all of the usual ignition components (coil, wires, plugs, cap, rotor). What else am I missing?? Internal carb problem??

The funny thing is that it's now running great at slower speeds and even accelerates good on the flat...

 

[TDHofstetter]

Hmmm... it may be time to check compression. Not that my '85 is what I'd call "musclebound", of course...

 

[MDJEEPER]

Hmmm... it may be time to check compression. Not that my '85 is what I'd call "musclebound", of course...

No...these are not what you'd call high horsepower street rods, but can yours hold 60 MPH in 4th gear on a hill??

 

[TDHofstetter]

I'm... not sure, to tell the truth. I oughtta' take it out & wind it up & find out... after I figure out just how far off the speedo is (it's a LONG way off).

 

[MDJEEPER]

Here's something else that's strange...the stepper motor on the BBD carb does not seem to be moving the rods, so I decided to go looking for the O2 sensor that tells the computer how to engage the stepper motor....I can't seem to find it down by where the tailpipe connects to the manifold! I am wondering if the exhaust manifold was swapped out at some point for a model off of an older AMC 258 i6 / 4.2l .

I did find one little sensor, but this looks like maybe the manifold heater sensor??

 

[TDHofstetter]

The oxygen sensor should be right about here:

One thing: Is the electrical plug plugged into the back (firewall) side of the carburetor, at the stepper motor? If it's not, that Jeep may have already been "Nuttered":

The "Nutter" Bypass

If it IS plugged in, it may have been Nuttered anyway - you may need to check inside thw wiring harness to find out for sure.

If it hasn't been Nuttered, and the stepper still isn't stepping, we gotta' either Nutter it or track down the oxygen sensor & test it to see whassup. That could have a pretty profound impact on how the Jeep runs.

EDIT: That last picture looks like your temperature sending unit.

 

[MDJEEPER]

Nope. I don't have an O2 sensor that looks like that. I don't even have a space for one that has been plugged. I also don't see an "anti-knock" sensor (or place for one) in front of the carb on the intake. Also, there's no heat riser "box" on the manifold either. Baiscally, I've got a manifold that does not contain most of what the manual describes (though, to be honest, I don't know what was used on the 49 state motors and what was used only for the California models.)

The wiring harness on the stepper motor is connected, but obviously not working, as the rods are fully extended and do not "constantly" move like described in the manual.

There is no obvious nuttering on the distributor side of things and the wiring harness seems completely intact with the appropriate wires running into the firewall to the computer.

A mystery indeed...What was the PO thinking???

 

[TDHofstetter]

Indeed - we all wonder that.

EDIT: With a little application of "clever"... we could hook up an ad-hoc O2-sensor simulator just to get that Jeep Nuttered...

 

[MDJEEPER]

Indeed - we all wonder that.

EDIT: With a little application of "clever"... we could hook up an ad-hoc O2-sensor simulator just to get that Jeep Nuttered...

OK! Tell me more! I am intrigued by your simulator idea!

 

[TDHofstetter]

OK - first thing we need to do is find the plug (from the wiring harness) that connected to the original oxygen sensor.

Next... go to Radio Shack and buy the following two items:

47 ohm 1/2W 5% Carbon Film Resistor pk/5 - RadioShack.com (47-ohm resistor 5-pack... you only need ONE of these)
1.5K ohm 1/2W 5% Carbon Film Resistor pk/5 - RadioShack.com (1.5K resistor 5-pack... you only need ONE of these)

Select ONE resistor from each pack. Wrap a strip of masking tape around it and write the value of the resistor on the tape so you don't have to think about the color-code bands painted on the resistor (I hate peering).

For reference, the color bands on each of those resistors should be:

47 ohms = yellow - violet - black - gold
1.5K = brown - orange - red - gold

(or you can doublecheck 'em with a multimeter set to resistance)

Ok, now... connect the two resistors together - one lead each - and connect a short (12" -> 24") pigtail wire to that connection. That wire should be any color except red and black. Yellow is good, or blue, or orange, anything but red and black.

Connect a RED wire to the other lead of the 1.5K resistor (do NOT MAKE A MISTAKE HERE - connect it to the 47-ohm resistor and you risk blowing all the smoke out of your computer).

Connect a BLACK wire to the other lead of the 47-ohm resistor.

To recap... your wires should be

RED
|
1.5K ohms
|
|- YELLOW (or blue, or whatever)
|
47 ohms
|
BLACK

Cool? Cool.

Find a good ground someplace on the motor. Securely SECURELY connect the BLACK wire to that ground.

Connect the RED wire to the (+) terminal on the battery.

With your multimeter, verify that the voltage on the YELLOW wire is now between 0.35V and 0.5V. It'll vary a little, depending on the battery voltage, but it should be pretty close.

If that voltage is right, we're ready - connect the YELLOW wire to the oxygen sensor's harness plug. You've just simulated an oxygen sensor in a near-perfect neutral (ideal) fuel mix environment. Start the engine and let it warm up. When it's up to temperature, the computer will believe it's reading the most wondrous marvel of all - a perfect, unchanging fuel mix. It'll neutralize the carburetor, and you can unplug the carburetor at that point.

 

[MDJEEPER]

OK - first thing we need to do is find the plug (from the wiring harness) that connected to the original oxygen sensor.

Next... go to Radio Shack and buy the following two items:

47 ohm 1/2W 5% Carbon Film Resistor pk/5 - RadioShack.com (47-ohm resistor 5-pack... you only need ONE of these)
1.5K ohm 1/2W 5% Carbon Film Resistor pk/5 - RadioShack.com (1.5K resistor 5-pack... you only need ONE of these)

Select ONE resistor from each pack. Wrap a strip of masking tape around it and write the value of the resistor on the tape so you don't have to think about the color-code bands painted on the resistor (I hate peering).

For reference, the color bands on each of those resistors should be:

47 ohms = yellow - violet - black - gold
1.5K = brown - orange - red - gold

(or you can doublecheck 'em with a multimeter set to resistance)

Ok, now... connect the two resistors together - one lead each - and connect a short (12" -> 24") pigtail wire to that connection. That wire should be any color except red and black. Yellow is good, or blue, or orange, anything but red and black.

Connect a RED wire to the other lead of the 1.5K resistor (do NOT MAKE A MISTAKE HERE - connect it to the 47-ohm resistor and you risk blowing all the smoke out of your computer).

Connect a BLACK wire to the other lead of the 47-ohm resistor.

To recap... your wires should be

RED
|
1.5K ohms
|
|- YELLOW (or blue, or whatever)
|
47 ohms
|
BLACK

Cool? Cool.

Find a good ground someplace on the motor. Securely SECURELY connect the BLACK wire to that ground.

Connect the RED wire to the (+) terminal on the battery.

With your multimeter, verify that the voltage on the YELLOW wire is now between 0.35V and 0.5V. It'll vary a little, depending on the battery voltage, but it should be pretty close.

If that voltage is right, we're ready - connect the YELLOW wire to the oxygen sensor's harness plug. You've just simulated an oxygen sensor in a near-perfect neutral (ideal) fuel mix environment. Start the engine and let it warm up. When it's up to temperature, the computer will believe it's reading the most wondrous marvel of all - a perfect, unchanging fuel mix. It'll neutralize the carburetor, and you can unplug the carburetor at that point.

Gotcha. That is indeed a very clever idea!!

Any suggestions on how to identify the what should be the oxygen sensor harness? The PO has a bunch of the old connectors just tie wrapped together up by the firewall. The wiring diagram I have does not show a color or other identifying marking for that sensor.

Worst case, can the stepper motor pins be mechanically moved?


BTW: Why do you prefer the "modified" Nutter, rather than the "original" Nutter (the stepper motor pins in the full rich position??

 

[TDHofstetter]

The wire leading to my O2 sensor is solid black, rubbery feeling. All the other wires in that group have nylon shells, so they feel stiff... but the one leading to the O2 sensor is much softer & rubberier.

I like to leave the carburetor in a "middling" position, neither particularly rich nor particularly lean. Too rich and you'll get 8 MPG. Too lean & you may warp a valve.

The stepper can be moved - electrically - but it's VERY SLOW and tedious. Gettin' it done takes shuffling wires around one step at a time... easier with four pushbuttons pressed sequentially. Another buncha' clever would build a stepper driver that'd let you turn it where you want it...

 

[MDJEEPER]

The wire leading to my O2 sensor is solid black, rubbery feeling. All the other wires in that group have nylon shells, so they feel stiff... but the one leading to the O2 sensor is much softer & rubberier.

I like to leave the carburetor in a "middling" position, neither particularly rich nor particularly lean. Too rich and you'll get 8 MPG. Too lean & you may warp a valve.

The stepper can be moved - electrically - but it's VERY SLOW and tedious. Gettin' it done takes shuffling wires around one step at a time... easier with four pushbuttons pressed sequentially. Another buncha' clever would build a stepper driver that'd let you turn it where you want it...

So, what you're saying is that Nutter wasn't concerned about fuel mileage! 8 MPH!!??

Yes, a stepper motor with a manual override would be clever!

I was thinking that there might be a way to manually move the pins if you were to physically remove the motor from the carb? It seems like I heard about someone doing something like that before...

With all of the other surprises I have already found on this project, I think I need some sort of back-up plan in case the O2 harness is MIA....you know, like (apparently) the original manifold!

I don't have time tonight to undo all the wire ties but will do that tomorrow. Will post a picture of any wire that looks like what you described to verify.