I need help...fuel starvation?

[IMHB]

I have a 1999 5.7 GSi with throttle body EFI.
The motor will run at high speed 1500rpm and above just fine. When I go to neutral, and the motor is suppose to go to a nice idle, it coughs and coughs and coughs, then sometimes dies, and sometimes it will catch and then idle very rough, the idle sounds like it's a hot rod with a very radical cam.. I have checked to make sure there is NO water in the gas.
I have replaced the Volvo fuel cell ( filter, low pressure and high pressure pump all in one ) with a brand new one.
This didn't help. The injectors look to be spraying a nice spray. I am not sure how the EFI system switches from high RPM to low RPM to makes the motor idle.
ALSO. I am wondering what the other part of the EFI does.. where the carburetor use to be there are two EFI sprayers, which spray straight down into the throats, and then something else at the rear of the EFI made out of cast aluminum, looks like it's held on with two star drive screws and has what looks like it might be a diaphragm in it, not sure what the something else does.....Any thoughts or any comments will be appreciated....Thank you...Harry

 

[Fun Times]

Re: I need help...fuel starvation?

When I go to neutral, and the motor is suppose to go to a nice idle, it coughs and coughs and coughs, then sometimes dies, and sometimes it will catch and then idle very rough, the idle sounds like it's a hot rod with a very radical cam.]

Hi there, Your description resembles more of an IAC (idle air control valve) problem vs a fuel problem.

The location of the IAC in the second picture is on the right side. It's the valve with the 4 wires going to it.

Description,
Boatinfo - Volvo Penta WT series Engine EFI System Service Manual

Diagnostics procedure,
Boatinfo - Volvo Penta WT series Engine EFI System Service Manual

 

[IMHB]

Re: I need help...fuel starvation?

I found the problem..it was a "MOUSE or RAT".. he chewed a little hole in the bottom of the MAP sensor hose.