[96Lt1civi]

Hello,
I have a bit of an odd scenario. My car (96' B4U) runs great at every point in the rpm range except 1300rpm.
If I raise the rpm in park to 1300 and hold it there, it runs rough and shakes (but not like a bad miss). As soon as I raise or lower the rpm away from 1300 it smooths out instantly.

I think I can feel it driving as well, but it feels a bit more like a flat spot than roughness when moving.
It runs perfect other than this, so I'm not really concerned about it. I'm mostly just curious why it would do something like this and at such a specific rpm.

 

[95wagon]

I see it is an OBD1 swap.
If you have the original PCM it might be telling to pop it back in and test
This might point at or away from calibration issues.

 

[96Lt1civi]

Today I got around to reinstalling my OBD2 PCM. I went for a drive (which was an interesting change on its own) and there was no change in the 1300rpm vibration. Could the harmonic damper cause this if it worn or missing some rubber? Mine is showing all of its 273k miles.
I'd also like to revise my previous statement, its not so much as if its running rough but like an unbalance almost.

 

[stonebreaker]

1300 rpm is the stall speed of the stock converter. I don't see how the converter would make the engine feel unbalanced, but the fact that the issue occurs at just the stall speed of the stock converter seems a little coincidental, yes?

 

[96Lt1civi]

1300 rpm is the stall speed of the stock converter. I don't see how the converter would make the engine feel unbalanced, but the fact that the issue occurs at just the stall speed of the stock converter seems a little coincidental, yes?

That is a good point, I wonder if it is related.
I will say that I've been doing this in park/ neutral and that the TC operation does feel normal.