Hey all, I bought a 91 Firebird with the tbi 305 a few months ago. Since then I have been trying to pin down a problem with the acceleration. When I press the gas pedal from a stop the car feels like it has weak acceleration and feels like it is bogging but if I press it about a centimeter more it jerks and suddenly takes off. It also does the same thing after it shifts into second. It's pretty bad after the car has been sitting for a few hours and is cold but also happens to a lesser extent when it's warm. So far I have replaced cap, rotor, plugs, wires, tps, and fuel filter and the car isn't throwing any codes. Also I have only been able to get a max of 14 mpg out of it even on a 140 mile highway trip. Any help is appreciated thanks!

 

Put a scan tool on that vehicle and look at the data stream. A fuel pressure tester would also be a good idea.

What is the fuel pressure when the bog occurs?
What is the short- and long-term fuel trim?
How many O2 cross-counts?
What is the O2 voltage when the bog occurs?
Is the knock sensor retarding timing when the bog occurs?
What temperature does the computer think the engine is? Is it realistic?

 

Is the TV cable hooked up and adjusted correctly?

 

After I get out of work I'm going to look into the fuel pressure tester. Can you recommend an affordable scan tool?

Also, about the tv cable, when I bought the car it wasn't adjusted correctly as far as I could tell so I adjusted it click by click over a period of a couple weeks until it shifted tight but not hard and so far it seems ok.

 

A used professional-grade scan tool will be five times as helpful as a brand-new consumer-grade junk scan tool.

I have had excellent success with the old Snap-On "Red brick" MT2500/MTG2500. Either one is a "winner" for occasional use, and there's always a selection of 'em on eBay and sometimes on craigslist depending on where you live.

As long as you buy one with software new enough for your vehicle, and the appropriate tool-to-vehicle adapters, you should be set.

 

I think I may have solved the problem. A few months ago I bought a Pro Flow air filter but it didn't mount up correctly and was loose. Yesterday I put the stock air cleaner back on with the appropriate wing nut and the problem seems to be gone. Is it possible that air was being sucked in from under the ring that sits on the throttle body since it was so loose?

 

Anything is a possibility. I have no trouble believing that a low-quality, poor-fitting air cleaner could cause a driveability problem. I'm not sure HOW it would cause that problem...but if it's fixed, it doesn't really matter any more.