Bored Throttle Body and Bypassed NSS

[Garthbmn7]

First I was having issues with the NSS. Since mine was cracked from trying to get it off last time and a buddy had a spare, I cut the wires and bypassed the NSS. No problems jeep ran fine. In the meantime I bored my throttle out to 60mm, below the valve/flapper/plate/whatever you want to call it. So the plate still seals fine. I also reset the throttle valve cable and pulled the battery terminals and turned the key to erase the computer. Put the TB back on and went for a spin. Bit more umph but lots of sputtering and engine cut in and out. Transimission shifted just fine. Repulled the negative post and checked all the connections. Now I'm just like Sammy Hagar and can't get my [XJ] out of 2nd gear. Shifts from 1st to 2nd at 4500RPMs, still has the sputtering and if I rev the engine it will drop way down and sometimes die. Almost like driving a manual and pushing in the clutch. Do I need the NSS hooked back up to get everything back to normal? How would the NSS control the sputtering and coughing from the engine?
TIA for any and all advice. Tried searching and could not find any answers on this.
98 XJ 4.0L 167K aw4
thanks
Garth

 

[87manche]

yes, you need the NSS hooked back up. it's not just for nuetral safety, it's the range selector for the TCU. Without it the TCU doesn't know what gear the shift lever is in, and since the TCU controls the shift solenoids it likely thinks you've got the selector in the 1-2 range.

 

[Garthbmn7]

So that should take care of the tranny issues but will it address the stumbling and idling issues?

 

[87manche]

Don't know. Fix one problem at a time. I suppose it's possible that the TCU is doing weird things like locking and unlocking the TC without the NSS inputs.
Hard to say. Bypassing the NSS may have even disrupted some other sensors ground. put it back to stock and then we can start over diagnosing the poor running

 

[Jess]

NSS has nothing to do with how the Jeep shifts!!!! I have the NSS completely unhooked on two of mine and they run, idle, and shift just fine.

 

[87manche]

NSS has nothing to do with how the Jeep shifts!!!! I have the NSS completely unhooked on two of mine and they run, idle, and shift just fine.

the NSS is also the range selector switch for the aw4 correct?
certainly looks like it to me in teh FSM.
if the range selector is disconnectd how does the TCU know what gear the shift lever is in?
this certainly looks like a range selection switch to me.

 

[Jess]

Mine runs fine without it...As far as I know the only purpose of the NSS is to make the correct connection to start the vehicle and turn the backup lights on and off.

 

[Jess]

I think I read somewhere that you have to adjust the tps after the TB has been bored.

 

[lawsoncl]

Mine runs fine without it...As far as I know the only purpose of the NSS is to make the correct connection to start the vehicle and turn the backup lights on and off.

The NSS also has two wires that tell the TCU when/if you're in (1-2) or (3). If you unhook the NSS and jumper the starter connection, the TCU will always believe you are in either park, reverse, neutral, or (D) since the switch does not connect either of these two lines in those positions.

I'm thinking the original poster has messed up the TPS.

 

[87manche]

thank you for that clarification. I knew that the NSS had something to do with telling the TCU what gear it was in.
So, it's possible that the original poster has also wired his NSS to tell the TCU that it's in 1-2 all the time.
I'd double check the bypass at the NSS and then chase the TPS as suggested

 

[Jess]

the conncetion to make it start is pins B and C (which is both park and neutral). 1-2 are pins A and H, 3 is pins A and G, R is pins A and E.

How would his transmission not shift correctly or think he is in 1-2 when, if correctly done, only pins B and C are connected?

 

[87manche]

perhaps it's not been correctly done.
hence checking the bypass wiring, then moving on to the tps.

 

[Garthbmn7]

Took the broken NSS and pieces from another one and put one back together and resoldered the wires so the NSS is correctly wired again. Unhooked the battery again and reset the computer. Still does not want to shift out of 1-2 until you reach redline. So if I am on the interstate adn get to 75-80 at redline then the tranny will drop into 3rd. Is there a quick way to check the TPS? I am out of town until Sunday. Happy turkey day everyone. but will start working on it again when I get back.
Thanks guys.
Garth

 

[Jess]

to check the tps:
1. using a high-impedance digital voltmeter, connect the positive probe to the center terminal and the negative probe to the ground terminal (black wire). (Note: This is done by back probing the electrical connector (don't unplug the connector from the TPS).
2. With the ignition ON, slowly move the throttle lever until it is wide open and observe the reading on the meter. With the throttle fully closed it should read greater than 200 millivolts. With the throttle fully open, it should read less than 4.8 volts. If the voltage readings are incorrect, replace the TPS.

you should also check the throttle valve linkage.
for the 4 speed transmission:
1. rotate the throttle lever on the fuel injection unit to the wide open position
2. hold the throttle lever open and allow the cable plunger to extend all the way, which automatically adjusts the cable. Once the plunger is fully extended, release the throttle lever.

I would adjust the throttle valve linkage first and then drive it and see if that helps.

GOOD LUCK!

 

[Garthbmn7]

It was the TPS :doh: . Got a new one and everythign works fine again.
Thanks everyone for all the information.
Garth :clap: