I'm having problems with idle. Its a vortec 4.3 cmpi. Idle has a fast shake. My pressure is at 52 psi running. Its not holding pressure after fuel pump stops after fuel prime. Injector assembly was replaced about 15,000 miles ago and fuel pump was just done with sending unit and pulsator. Pinched return line when running and pressure shot up but after a hard pinch, not light. Pinched pressure line after key was turned and still lost pressure. I hope that the bad idle is due to under pressure, but confused as to what is the culprit since everything has been replaced including filter. It also has a hard time starting after it sits from operating temp. Sometimes I have to hold the gas pedal down. Can someone help me figure this one out?

 

Just wanted to post about what I found. The pressure line inside the upper intake had a small leak filling up the plenum and thining the oil! I noticed the temp gauge go up one time before i dissasembled. It enters through a small hole in the upper plenum falling into the lower intake. If this has fixed the bad idle, I don't know yet. But i know it will hold pressure now unless the regulator went recently too. I will post after i have it up and running for those of you who are curious.

 

O.K, its done. It took care of the shakey idle for right now running it till operating temp. Three of the plugs could still be carbon fould. I will clean them tomorrow. It may idle even better. It wouldn't start after letting it sit because the fuel in the upper plennum emptied into the cilinders that where open causing a flooding conditon. Thats why I had to give it gas to get it started(more air).

I hope this helps people with same problem.