okay i have a 89 firebird formula. it runs fine but every once in awhile the engine would just turn off but never when i was actually driving. now its doing it when im driving. it just shuts down and i have to turn it off then start it again. it does turn back on after but i have no idea what is wrong with it. PLEASE HELP!!!!!! also the RPM is always going up and down even when on park...

 

What engine do you have?

 

i have a 305 engine v8 5.0 liters

 

tpi or tbi engine?? Common problem with GM's are fuel pumps, and very common on third gen vehicles. I would start testing fuel pressure, TPI should be 43.5psi at idle, and your pump may be getting weak. Do you have a Check Engine light???

 

It's hard to diagnose without knowing which engine you've got for sure since there are several differnet 305's. If you've got a tpi I would begin by checking fuel pressure like 91interceptor said. Also, take the rubber air intake hose off and clean the throttle blades really well with some carb and throttle body cleaner. You should also remove the iac valve from the throttle body and clean it. Finally, check the voltage on your throttle position sensor. This is all routine maintenece for these engines but if it hasn't been done for a while it WILL cause the idle problems that you're describing. If allowed to persist long enough I suppose it could cause stalling. Anyway, this might be a really easy fix that should take less than an hour. Hope this helps.

 

agreed cleaning the port and installing a new IAC fixed my horrible idle, and if throttle seems unresponsive, sluggish or in general engine just feels like it wont go when you push the pedal down, check tps voltage (its easy and quick to do).... tps voltage being off would affect idle.....