I went to take the 93 SWB out for a drive today and a weird problem cropped up. It will start fine and after idling well for a couple of minutes it will start this oscillation where it seems like it is going to stall and drops to about 500 rpm, then recovers and comes back to normal for a few seconds, then repeats. If I shut the motor off and restart it the same pattern will happen. It starts great then gets into the oscillation. Adding some throttle does not seem to make a difference in the oscillation except making it recover to a higher rpm when it jumps back up.
After messing with it for several minutes like this the check engine light came on with a code 17. Would the TPS really make it oscillate like that or could it be something else? I was recently facing some issues with the advance on the timing at higher rpms. I replaced the distributor and afterward it was running better than it ever has across a variety of driving conditions for about a week until this happened. Unfortunately I don't think the TPS is interchangeable with my 95 to make for a quick and easy test. If I want to test it with multimeter, what is the test procedure? Since I recently messed with the distributor, is it more likely that I messed something up with that and maybe the TPS is ok?