Thread: 3.5 EFI stalls on low revs - why?

Don't know what F.I. setup you have, does it still have the original Plenum on top of the inlet, if so does it have the Idle Air Control (IAC) valve on the rear of the plenum.
If so check first that it is tight (3 allen bolts), remove and clean valve and seat with carb cleaner and a soft bush, brass or non melting plastic, also check if rubber hose to fuel pressure regulator valve is not leaking.
Hard to say what supercharging will do to these Vacuum operated valves, check with supplier of Blower, Regards Frank.

Thanks Frank
The motor with FI has a Plenum on top so I will check the idle control and clean as you suggest

Will check same on other normal efi 3.5

Pressure regulator - the FI 3.5 has an after market pressure regulator - and it seems to have a minor leak - has purple/red stain of fuel on it. Why would this affect low idle? Not sure how to address leak as when I got this running set up with the FI it did not have leak or stall issues - was in a manual though so wonder if that is part of the difference or now highlights the issues.

Engine pic below - you can see the blower and the purple in the background above the air intake on the firewall is the fuel regulator


SKiboy

Being a blow through system can upset sensors originally operated by Vacuum, esp. throttle body sensors. Fuel Pressure Regulators (FPR) usually operate off a Vacuum source, if the FPR is leaking or not maintaining pressure between itself and the injectors, then problems can result.
Consult installation instructions on how forced blow through systems affect vacuum sources,good luck, Regards Frank.
P.S. An Intercooler would certainly be beneficial, also.

Stick a wide-band O2 gauge on it and all will become clear. If it's too rich and swamping or too lean and dying it'll be obvious.

Originally Posted by Tank

Being a blow through system can upset sensors originally operated by Vacuum, esp. throttle body sensors. Fuel Pressure Regulators (FPR) usually operate off a Vacuum source, if the FPR is leaking or not maintaining pressure between itself and the injectors, then problems can result.
Consult installation instructions on how forced blow through systems affect vacuum sources,good luck, Regards Frank.
P.S. An Intercooler would certainly be beneficial, also.

Thanks Frank - but this engine worked fine in The109 so this is a new issue after transferring the complete system to a new vehicle.

And the other truck has same issue exactly and it is not forced induction - exactly the same problem.

Originally Posted by Dougal

Stick a wide-band O2 gauge on it and all will become clear. If it's too rich and swamping or too lean and dying it'll be obvious.

Stick the gauge on what - the intake or out?
Don't have an O2 Gauge unfortunately