I have a tbi 305 motor in my 88 firebird and have touble getting the car to run. When I crank the car it cranks fine but it takes over three to four seconds to start to run. This is followed by stumbling (bouncing from 500-700rpm) and thick black smoke weather the engine is warm or cold. I have replaced the Tps, Iac, cleaned TB, installed msd 6AL, GM blaster coil, set timing (base at 4 degrees), new cap and rotor,checked injectors and nothing seems to help. What could my problem be? I belive I am getting enough spark and air just too much fuel. The car also has a open element air cleaner and a flowmaster exhaust and afpr which is set lower than stock. also if any one has pic of what a 88 TBI computer chip looks like post a pic and what are the two small electronic boxes near the computer one is black and one is yellow they both have AC on them. Thanks for the help.

 

You said you lowered your fuel pressure?
Are you sure your base timing is set? You might want to double check or play with it until the engine likes to idle low @ ~550-600rpm, and then turn off and see if it's easy to start. A hard start usually indicates too much advance and remember to disconnect the tan wire before moving the distrib (so ecm doesn't advance).
You might want to get a scan tool hooked up and look at all the values like vacuum, TPS, etc. Maybe you have weak starter that's on it's way out.

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, Jon (350 TBI!)
91 Red My website

 

The start seems brisk so I dont think that the starter is at fault. I lowered the fuel pressure to see if it made any diffrence but it did not so I put it back where the factory had it (tab half way up slot)I also disconnected the tan wire to set the timing to 4 degrees for the base according to the tab behind the water pump. But maybe I will double check it tonight to see if any diffrence can be made. Also can a Coolant temp sensor cause this problem and what values of resistance should I see at cold and hot. Right now I get 1200 cold and 350 hot(ohms).