I have a 89 non turbo. and when i run it for a while and turn it off and then use it again it starts ok, but then the rpms drop, and i loose the acceleration, even if i step on the gas, the car does not accelerates, any one had this problem before? i changed the spark-plug wires and also used the injector cleaner fluid, but didn't solved the problem.

 

sounds like a bad sensor somewhere... I'd say the first step may be to resolder your ecu or do engine code check.

Things around the throttle body may be sticking... check operation of tps and adjust it. Also make sure cold and hot throttle systems are functioning properly.

 

First, scan your ECU:
http://www.1300cc.com/howto/how2/codes.html
http://home.rmci.net/panther/89_91ecu.htm

If you don't get any codes/errors then:
Set the TPS and look for vacuum leaks or go through the trouble and replace all vacuum hoses. Check all electrical connections. Make sure that the AFM's cone moves freely back and forth. Test the pressure sensor.
And for cheap possible fixes, replace the spark plugs/fuelfilter/airfilter/o2 sensor.....
Download the FSM and read the fuel/emissions/engineelectrical chapters:
www.iluvmyrx7.com
www.fc3s.org

If if nothing above helps, be more specific with the problem. How old is the car? Mileage? Is problem new or gradually getting worse? Regular maintenance? Compression? Is this an idle revving problem or driving hesitation issue?