91 tpi s/d. at start it takes a few times to get it to start. when idling its low and sometimes stalls. give it some gas and there is popping in the plenum and is hesitating. fuel pressure at idle is between 35 and 38psi. last year it got Southbay injectors and an AFPR. i just replaced the fuel filter. after it warms up it runs starts and idles fine. when off pressure holds around 10 psi. i recently checked and cleaned the iac.

ive got the afpr adjusted all the way down. no codes are flashing.

suggestions?

 

35-38 with the engine running and the vacuum line hooked up is normal-ish. What is it with the vacuum line capped off?


Try covering all your bases. Ignition, fuel, egr, vacuum issue(pcv etc). Check the plugs, see if it's been lean or rich when cold.

 

My car showed fuel pressure within spec too. Replaced everything under the sun. I took it to a good mechanic and he pulled the return line and found the fuel barely coming out. Fuel pressure at idle doesn't guarantee you are getting enough VOLUME when driving down the road. They put in a new GM fuel pump, pulsator, and sock. Drives better than new. Good luck.