[TFCSD]

Have you ever changed the spark plugs ?

A few years ago. But, it is idling smoothly until it reaches operating temp then it gets rough when the RPM drops to ~100

 

[Bob Lincoln]

One thing I think we all missed, and it's basic, is to do a full tune-up. These engines eat ignition rotors, and so they need to be replaced every 15K miles. They also burn the forked tips of the ignition wires inside the cap, and so at 15K miles you can remove the wires from the cap, turn them 180 degrees so that the other side of the fork faces the rotor. Then at 30K miles, the wires need to be replaced.
So, replace plugs and ignition rotor at 15K miles, and at 30K miles, replace the wires and distributor cap. If you haven't followed these intervals, this could cause stumbling at idle. Once I missed the schedule, and at 20K miles, I had a sudden no-start. Took me 2 days to diagnose the burned ignition rotor, and once replaced, it started immediately and was smooth.

 

[ImperialCrown]

You will want the OEM Champion RN12YC Copper Plus for best burn.

 

[TFCSD]

One thing I think we all missed, and it's basic, is to do a full tune-up. These engines eat ignition rotors, and so they need to be replaced every 15K miles. They also burn the forked tips of the ignition wires inside the cap, and so at 15K miles you can remove the wires from the cap, turn them 180 degrees so that the other side of the fork faces the rotor. Then at 30K miles, the wires need to be replaced.
So, replace plugs and ignition rotor at 15K miles, and at 30K miles, replace the wires and distributor cap. If you haven't followed these intervals, this could cause stumbling at idle. Once I missed the schedule, and at 20K miles, I had a sudden no-start. Took me 2 days to diagnose the burned ignition rotor, and once replaced, it started immediately and was smooth.

Did a tune-up as suggested (spark plugs, plug wires, cap, and rotor). It had normal wear and tear with no surprises. It made the car a little happier (~10% better this and that) but still has the same problem. I've done about a dozen things that made the car run a little better but not the fix.

 

[TFCSD]

Need some info on the Neutral Safety Switch (NSS). In the manual it states the NSS is an input to the computer used to control fuel, idle, and timing. I compared diagrams in the original OEM service manuals and Chilton's manual and they are the same. Round connector with three terminals. The neutral safety center terminal is normally closed and shorts to the casing for P and N for the starter relay. For neutral safety it should open on R, D, D1, and D2. The outer terminals (1,3) are for the reverse lights and is normally open unless in R. This is what I summize from the manuals and if tested should read as only switches (open or closed) with no resistive states in between and need to know if I'm correct so far. My old NSS reverse light switch works fine if I press the center tab, but the neutral safety contact is constantly open. What has me confused is, if my old neutral safety contact is constantly open, my car should not start, yet it does. To add to my confusion, the new NSS I bought, TE121, the reverse contacts seem to work if I press the center tab, but the neutral safety contact is constantly open and no matter how I actuate the device (does nothing). This leads me to believe the new NSS is defective right out of the box if it does not change. Unless the NSS is not being used as a neutral safety which means both old and new switches are working. So I need un-confused and expect there was a design change sneaking in the background.

 

[chuzz]

Where did you get the new NSS? If at your local advancezoneoreilly, then there's the problem. I NEVER purchase electrical parts from any of them. Having worked for two of them, I KNOW that there stuff is generally cheap crap. Get a genuine Mopar NSS if you want to be sure.

 

[Vern14]

Only use mopar brand sensors in your mopar . All others may cause more or different issues .

 

[Bob Lincoln]

Need some info on the Neutral Safety Switch (NSS). In the manual it states the NSS is an input to the computer used to control fuel, idle, and timing. I compared diagrams in the original OEM service manuals and Chilton's manual and they are the same. Round connector with three terminals. The neutral safety center terminal is normally closed and shorts to the casing for P and N for the starter relay. For neutral safety it should open on R, D, D1, and D2. The outer terminals (1,3) are for the reverse lights and is normally open unless in R. This is what I summize from the manuals and if tested should read as only switches (open or closed) with no resistive states in between and need to know if I'm correct so far. My old NSS reverse light switch works fine if I press the center tab, but the neutral safety contact is constantly open. What has me confused is, if my old neutral safety contact is constantly open, my car should not start, yet it does. To add to my confusion, the new NSS I bought, TE121, the reverse contacts seem to work if I press the center tab, but the neutral safety contact is constantly open and no matter how I actuate the device (does nothing). This leads me to believe the new NSS is defective right out of the box if it does not change. Unless the NSS is not being used as a neutral safety which means both old and new switches are working. So I need un-confused and expect there was a design change sneaking in the background.

I don't think you're interpreting the function and states of the switch correctly.
The center wire goes to ground. One of the outer wires goes to the backup light switch and the other to the starter relay. The switch only matters to starting, and not running. It has no effect once the vehicle is started.

 

[TFCSD]

I don't think you're interpreting the function and states of the switch correctly.
The center wire goes to ground. One of the outer wires goes to the backup light switch and the other to the starter relay. The switch only matters to starting, and not running. It has no effect once the vehicle is started.

According to the OEM service manual the NSS does several things including idle. The center terminal does go to ground after passing through a normally closed switch. Included info that has me wondering why my NSS is not functioning like the manuals says. I figured someone on allpar knows what's right.

 

[ImperialCrown]

The image below is for a RWD transmission, but FWD works the same way. The center contact terminal (#2) grounds to the manual (selector) shaft 'comb' in the P and N positions through the metal nub.
Selecting Reverse allows the nylon switch button to close a switch between the outer 2 contacts (#1 and #3) to send 12v to the rear lamps.
Switch continuities can be tested with a meter.