Have a 91 RS and just replaced TPS as scantool point volts too low. I've had this off idle hesitation (especially with AC on) that clears if I put more throttle into it or go beyond 1500rpm. If I'm in traffic and I give slight throttle it wants stumbles and if I let off the idle will drop to 200-300 or so and then recover back to 500-600.

New O2 sensor, new TPS, new plugs. no codes, all sensors seem to functioning properly. I do need a cap and rotor as it's a bit old.

ideas?

thanks

 

Do the following and I can almost garentee it'll help 100%: New wires with rest of ignition and readjust base timing. The car should run best at about 6 base but play with the timing until it idles well and you have better throttle responce. The only reason it's dipping down so low and coming back up is either because it's missing (choppy idle) or the IAC is saving your @$$. Also take a look at your voltage gauge, if your alternator isn't doing so well and dips noticable that could be your problem.

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, Jon (350 TBI!)
91 Red My website

 

This is just a suggestion but make sure that you have the firing order set correctly. I didn't and those are the same symptoms I had except the car wouldn't really go anywhere. I had the 6 and 8 wires mixed up. All is good now.

Also, maybe try an oil change?