Hey all,

I've got an 85 Firebird I've been working on slowly as I've had time. The first thing I noticed was at random times, the car would try to start speeding up while I'm at a complete stop in drive. Like it would quickly run up to 5k+ RPM and start trying to spin the back tires before I could react and the only thing that would stop it (albeit not great for engine / trans) was to slam it up into Neutral and then it wouldn't do it again for a while (like weeks to a month +). What could be causing that? I don't get a lot of time to work on it and I'm no expert on the 305 TPI. Also, had an issue where the radiator fan just quit working, noticed it on a trip out to the lake one day, just happened to look over and it was overheating, luckily I was less than an 1/8th mile from a gas station to pull over. Since then everything I can think of has been changed from the Thermostat, the Temp Sender Sensor, Relay, Fan itself, checked the fuses, absolutely no issues, I don't see anywhere where grounding could've come loose, nothing that should've been out of the ordinary. On the new fan the clip for the wiring harness was upside down, so I was advised (I thought it would've reversed the polarity) to push the connectors out and flip them upside down so the pins would line in right and actually be able to clip and hold again. Nothing has worked so far, hooked the new fan up directly to an old battery and it functions fine, so it's not that. I want to get these 2 issues fixed as I have someone interested in buying it, but if these can be easy fixes, I will be able to get a lot more out of the sale than I will with the buyer needing to fix them.

Thanks for any help in advanced!

 

The only way for the engine to rev up that much is for the throttle blades to open the far. Since it's mechanical, it's easy to troubleshoot. Either your cable is getting stuck, the blades are getting stuck in the bore (pretty unlikely) or the cruise control has a malfunction. Unhook the cruise control at the throttle body and while you're there, inspect the cable check for opening smoothness from the pedal etc.. If it's binding then you have an issue.

 

I had the same problem with my 87 Monte Carlo SS before I did the TPI swap. The motor was the original carbureted 305HO. One day, while cruising on the highway, I felt the motor trying to pull the car faster. I placed the gear shift in neutral and the motor spun up to redline and beyond. I put it back in gear and looked for a safe place to pull over while having my foot buried into the brake pedal. I did not want to turn the motor off while on the highway because I would lose power steering. I found a safe place to pull over and shut off the engine. My brakes were completely cooked and the car would not stop. It eventually coasted to a stop. I checked the throttle blades, secondary air valve, throttle was not stuck. Tried starting it and after about two seconds it would rev up past redline without my foot on the pedal. The only thing I noticed was that the catalytic converter was red hot. I believe that means there was raw fuel in the exhaust. After that. I did the TPI conversion and never looked back. I agree with Aliceempire that the engine has to be getting air and fuel to rev that high. In my situation, with the carb 305, I never found out how the motor was getting air and excess fuel at the same time. I had removed my cruise control years before. The car did run fine after it was towed home and the motor cooled off. By then I had already decided to go TPI.

Do the checks that Aliceempire says and post up your finding. I am real curious about your situation. Good Luck

Fred