I've got an 89 GXL with emissions removed (not by me, so couldn't tell you if it might have caused this issue). When running slow in 1st or 2nd, the car starts bucking repeatedly, sometimes pretty violently. Checked the TPS at the ECU and looks like it's dead on at idle, 1V narrow, .8V wide. Didn't notice any weird spots when calibrating it. Hitting the clutch seems to stop the bucking, too.

Possibly related, but maybe not, it idles high, around 1500 RPM, and often wanders/pulsates. rrrrrrrRRRRrrrrrrrrRRRRR, dropping down a few hundred RPM, and surging back up. Sometimes when it rains, it seems like it's a bit more stable, and around 1000.

Was looking around today and found that it looks like the neutral switch isn't working. Sits at 2V when the ignition is on but the engine isn't running, then goes to battery voltage if you actually start the car, Guessing it must be a broken wire or something, planning to poke around more tomorrow when I can get the car jacked up and look at the switch.

So, questions: 1, does this bucking/weird idle seem like a problem that could be explained by only a bad neutral switch? 2, is there another name for a neutral switch and any ideas where I can find one? Gonna see if I can salvage this one, but if I do need to replace it, I looked around and can't find any mentions of them for sale. I see lots of 3rd party neutral "safety" switches, which I assume are the neutral/park switches for an auto transmission and not the same as what I'm looking for.

 

Are you using an analog or digital multimeter? Did you check the resistance through the TPS? I'm pretty sure that's how the FSM says to test it.

idk about the neutral switch