Join Date: Feb 2009
Location: Largo, FL 33774
Did you pull the codes from the computer? You should do that before you do anything. The issue could be anything from an O2 sensor, to the injector, or the ground by the thermostat housing (the ground is for the O2 sensor and the computer). All will cause the engine to stall, run rich, and possibly stall. It could also be the fuel pump, and that would not give you a code.
First pull your codes. Then depending on your codes, I would start by cleaning the stud, and threaded hole for the ground (do it with the engine cold to avoid a water leak). I used a small round wire brush like you would use to clean a gun barrel, and some parts cleaner for the threaded hole, and a wire brush for the stud. Check the output of the O2 sensor, because it controls the mixture. Watch the injectors while the engine is running and after it is shut off, to check for dripping/flow pattern characteristics. It is difficult to check the fuel pressure, so I do not know how to do that without modifying the fuel line. There is supposed to be a connector that fits between the metal line and the nylon line connectors on the right by the AC compressor, but I have never seen one. There is an adapter made that can be screwed into the TBI, but you have to reshape your hard line to make it fit. Let me know what you find, I have has almost every problem possible with the LO3/5 that is possible.
Another thought, pull a plug on each side to check the color. it should be a light tan to almost white. If that is the color, it has the correct mixture, and your problem is somewhere else.
1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Hydroboost, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check https://www.impalassforum.com/vBulle...ion-parts.html