Since my rebuild is in the breakin stage, I keep the RPMs under 4000. But when I approach 3600-3800, I get a bad stumble. The car had this before the tear down and I managed to make the stumble intermittent by adding ground wires. Now the stumble is major.
I checked the TPS via, Zeitroniz, S-AFC and Rtek. They all show a notch/knee on the graph at 3600-3800 rpm when the car stumbles. The resolution of the graphs weren't so great so I plotted it on Excel to see if it becomes more pronounced.
Look at the graph. Major notch at the same point either sweeping up or down on the TPS. The sweep rate is that of rolling the power on smoothly to max. If I stab the accelerator, I usually don't see the notch. Also the notch/stumble is intermittent, which has lead me to this analysis.
All things add up that it is the TPS but I'm looking for a confirmation before I spend the bucks. Has someone seen a similar plot that can associate the notched graph to a failed or failing TPS?
BTW, it;s a 1988 AE TII rebuilt at 122K. Now has 160 miles since rebuild.

 

TPS is bad.


-Ted

 

the 3800 stumble is also a classic case of poor grounding.

If your graph is based off voltage and not off reference pin to pin, the problem is much more likely a poor ground.

Re-ground the engine and ECU. I'd also recommend an additional ground to the back of the block where the sensors ground to the engine.

 

Grounding:

http://www.aaroncake.net/rx-7/grounding.htm