I have been troubleshooting a problem with my 91 RX-7 with an automatic transmission. The problem is when I accelerate, in order to let the transmission shift to the next gear I have to lift my foot off the accelerator. Then it will shift. I have to do this through all four gears. This problem has not changed in two years (no better no worse). The Mazda dealer here in Madison Wisconsin could not fix the issue. They replaced two sensors which didn’t change anything. A local reputable mechanic I took it to said it was a vacuum problem, and regulated the pressure on the vacuum modulator on the transmission, and that seemed to take care of the problem until I disconnected the battery to put in a new radio, then the problem returned. Once again we regulated the pressure and that seemed to fix it. Yesterday I took it to the same mechanic after we replaced the battery, and he tells me the pressure is fine now, and is not sure what is causing the issue. The transmission fluid is good and has been changed regularly (every 25k). Has anyone seen this issue before? Any idea how to solve it? Any help is greatly appreciated

 

this might not help. but i had the same problem man. i tried everything i could until i said **** it and i swapped to a manual.

 

It seems like there is a problem with the vacuum modulator, but you say you've had mechanics take care of that. I don't see how disconnecting the battery can cause the problem to come back unless the S5 auto trans has some kind of electronic devices that interact with the vaccuum modulator, but I doubt it. Most vehicles from that era use either vacuum pressure or a cable directly attached to the throttle body to move the valve in the vacuum modulator. I've seen this problem on my friends BMW. We popped the hood and the cable had pulled out of the sheathing and would not retract, thus the vacuum modulator was always stuck in the wide open throttle position.

 

So is there a way to replace the modulator valve without a mechanic or would u recommend that it be done by a mech.?

 

its fairly easy to replace it. jack up teh car. look on teh driver side of the tranny. for the vaccum modulator. its by the oil pan. disconnect the line. and loosen the bolt and put a new one in.

 

you might want to check to see if you can adjust your existing vacuum modulator. If I remember correctly (I had an automatic 2nd gen 15 years ago), I've changed out my vacuum modulator and there is a small adjustment screw inside the vacuum nipple. It allows you small adjustment in shift points. I'm not sure if the original factory modulator has this or not but the one that was in my car had it.