We just put in a new V8 5.2 liter engine to replace the old one and it will start but it will only idle for about 30 seconds and then it dies. We can hear the fuel pump turn on, we replaced the fuel pressure regulator. We checked the throttle body sensor it seems to be okay. The fuel pressure is about 40 before we start it and within the guidlines of the chiltons manual while idle around 18. Is there any suggestions out there? My husband is a diesel mechanic and has a very creative mind but he is at his witts end and I don't know how else to help him. Any suggestions are welcome.

Does it just Die or is their a rough idle before it dies?

The Fuel Pressure should be around 31 PSI w/ Regualtor Vacuum hose connected and should increase 8-10 PSI with Vacuum hose disconnected.

It runs like it is choked and there is no throttle response. Then it dies. Could it be the map sensor? Thanks so much for the fast reply.

Does the Check Engine light come on?

The throttle body might need cleaned.
Throttle POsition Sensor might be bad, I have a test if you need it email me Joe dksob81@hotmail.com