there is an afterfire/backfire, how ever you call it, comeing out of the throttle, this is a problem that occures during accelaration causeing REALY poor preformance, up until i started adjusting the tpi it would also happen while just reving the motor while in park.
i have replaced the spark plugs and wires, distributor cap and rotor button, and the fuel filter but with no avail, all it seems to have gotten me is an unwillingness to start and some really hard starts... this a compleatly stock no frills 89' firebird, and any suggestion/advice would be much appreciated....

 

Dear ***, I thought you'd have given up by now. Way to stick with it!!

Check timing, should be set to 10 degrees BTDC with EST disconnected. If you don't know where the EST bypass connector is, I'll track down a picture.

How many miles on the motor? Timing chain could be old and skipping teeth.

I've seen references to vacuum leaks and low fuel delivery also being possible causes. Go over all the crappy plastic vacuum lines and made sure none are broken. Make sure the brake booster isn't leaking. Check fuel pressure, too. I'm sure the D-man can come up with a fuel pressure gauge.

If your TPS is out of adjustment, it won't help matters. To check it, disconnect the TPS and get 3 equal lengths of wire to connect it back up while giving room to probe with a multimeter. With car on (not running) and the throttle at idle, considering pin A on the tps ground (the top pin) and pin B positive (middle pin), should read a voltage of .54-.56 volts. adjust tps until this is obtained. Tighten TPS down, recheck to make sure it held the adjustment. now, with the multimeter still connected, *slowly* open the throttle and watch the voltage, and make sure it increases steadily, and it should reach a little over 4 volts at WOT. If the voltage is shakey as throttle opening increases, TPS is bad. Slowly close throttle watching for same signs.

Also, don't be afraid of the V6 board.. I don't bite.. much