i swapped my motor over to a 350 from 305 with the same tbi and aftermarket intake cam etc basically its a mild build. i took it to the track and was running 13.50's it was running good and reliably for the longest time. i put new injectors on it and it slowly aquired a sputtering problem. i thought it was the injectors so i swapped the stock ones back in. that didnt fix it. if i let it idle it will run for about five minutes then stall. at one point it would backfire through the exhaust now it seems to be through the intake. i changed out the fuel filter thinking it could have been dirty fuel and disconnected the battery now when i take my key out the fan continues running and it still sputters. any help will be appreciated.

 

is the SES light on? whats your fuel pressure at?

 

no lights are on. idk what fuel pressure is. i havent checked it. im about to just give up and swap to carb and just eliminate the comp. all together

 

check fuel pressure at idle and then rev it and check again. How old is FP?

 

i believe it is the stock fuel pump. the car has 78000 miles.

 

When you say it's 'sputtering', do you mean it seems to be getting too much fuel or too little? If it's too much, check the CTS - they can go bad w/ age. When mine went bad simply disconnecting it made the engine immediately start idling better and the injectors running like they should. If it's bad, it's less than $20 to replace.

If it's too little, check the fuel pressure as others have already suggested. It could be the fuel pump or the fuel pressure regulator diaphram. The regulator can be repaired w/o removing the throttle body.

You also mentioned the fan is running and I assume the engine hasn't run long enough for them to be on yet. The ecm might be getting a signal that the engine is hot, leaning the mixture out, and turning the fan on. Again, a bad CTS may be the culprit.

Finally, you can find out a lot by connecting a laptop up to the ALDL port and running WinALDL or TunerPro to monitor sensor signals to the ECM. You can buy a cable for a serial or usb port. A serial port cable can be built fairly easily. The software is available for free.

I'd definitely check some things out before tossing the TBI for a carb. But, that's just my opinion.

Hope this helps.