87 Firebird problem

Just got my very first bird, and I'm really loving it. Even though it was sitting for two years, the running gear is in fairly good shape with no leaks and such and I managed to drive it 200 miles back home without a problem. The car has had the battery replaced and the oil and filter changed, but little more in the ways of a tune up (tight budget). It did have a stalling problem recently that was fixed by replacing the throttle. Now it no longer stalls out. However, now I'll be driving around and hear a sound similar to if a rock struck the underbody. I can feel it in the gas pedal and the car will lose power for a split second and continue on. For the most part its random and very rarely happens when driving around town. On hills it happens a bit more and sometimes twice in a row. This did not happen until I had the throttle replaced. This is an auto tranny and shifts smoothly. Anyone know whats going wrong?


On a side note, I purchased this car intending to actually learn about whats under the hood. I've been told that older cars are easier to learn on. Its my second car and I still have a lot of learning to do, but I have done very minor things (fixed the brake light, worked on the headlight motor, replaced mirrors). So if its something I realistically can do without blowing the car up such as an adjustment, please let me know.

what engine do you have. a car that has sat for a few years is the worst thing that can be done to one, i have a 90 rs camaro w/ a v8, i let it set for 8 months , i did start it every weekend, drove it a couple of miles a week. i had to change the spark plugs. another problem could be " if its got FI" could be a bad injector, they do crystalize over time. my brother got a 86 firebird, 2.8 v6 for $900 that had sat since 1996, he got it in 2001. after a month he was replacing air massflo sensors, exhaust, fuel pump, then the computer went out. hope you get it lined out, good luck.

It is a carbureted 305 v8 firebird formula. The last owner told me that although it had been sitting for a bit, he ran the engine every few months. I really hated having to drive it all the way back home after it had sat for so long but shipping it would have cost more than it was worth. I've been going as easy as possible on it when I had to drive it (hard to do when given more power after being used to a v6) and plan to have it tuned up as soon as possible.

awsome, is it a high output? 305 is a good engine, my brothers '86 trans am has a carburated 305 ho,
that car is bad ass, it had 240,000 miles on the engine and tranny, we pulled out the motor and rebuilt it, also we had it bored it 30 over, which made it a 309, and some new hyperutectic pistons,
a cost of around $600 and that was getting the heads redone also. the car was dyno'ed at 175 rwhp
before the engine rebuild and mods, 245 afterwards.