Elvota

Acronyms

Regarding a 3.0, V6....

What is the VSV trying to do in regards to the Fuel Pressure Regulator? I seem to understand that the fuel pressure drops when vacuum is applied, but why and when does the ECU make this happen?

If I have a clogged line or bad VSV, would it be better to run the regulator with no vacuum ever... or rig things so it receives constant vacuum when the engine is running.

phorensic

I remember reading that if you remove the vacuum line to the FPR on the 3vze that you will get a constant (higher) 43 or 45psi at the fuel rail. I plan on doing this when I get my turbo installed so that I am on the safe side of the fuel situation.

It would make sense that the VSV will apply vacuum at idle or low-load conditions to lower the fuel pressure, thus "leaning out" the motor because the injectors will squirt less fuel per injection cycle. Kind of like boost-referenced FPR's that are sold to raise the fuel pressure as boost increases.

midiwall

There's been some back & forth about this on the 3.4L and I figure that the theory would match on the 3.0.

On the 3.4, the "fix" is to just plug the line that goes to the FPR - that will keep it open at max all the time. It's said that you should get a bit more pressure at all throttle settings, with the theory being that since you have more pressure at lower "skinny pedal" placement, then you should get a bit better response off the line.

I bounced back and forth through this before the S/C and never really came to a conclusion.

phorensic

Yeah, it's not really a fix for more fuel or anything, it's just to make sure that last 10% is squeezed out.. if you know what I mean. I think rising-rate FPR's are a band-aid before the real fix of installing bigger injectors. Hence I have purchased six 7mge 315cc/min injectors for my project and a Walbro 190 instead of just unplugging the vacuum line and hoping I get enough fuel, lol.

midiwall

There ya' go... RIGHT ON!

Elvota

So, if one was going for better MPG, not horespower, vacuum all the time to the FPU would be a good thing?

phorensic

Well, constant vacuum would probably create a low fuel pressure/lean condition. That's the reason for the VSV.

midiwall

Righto!

Dan_in_WI

I changed my timing belt and valve cover gaskets last weekend.

The timing seams great. I am still leaking oil. Oil cooler maybe.

I am running into a low idle speed problem. When I unplug the VSV for the FPU the idle picks up and runs fine.

What could be causing this? Should I just leave it unplugged or set the idle faster?

Dan_in_WI

Setting the idle faster didn't help smooth the idle at all.

Leaving the vacuum line off.

Any other ideas out there?

Alex 400

When you unplug it does the idle go up at all? my truck sits at about 950-1100 rpm at idle all of the time and shouldn't it be at like 800? could this be the vsv?

Dan_in_WI

The idle speed increases dramatically and smooths out when unplugged.

In contrast it barely runs when plugged in.

I double checked the lines in the FSM and they all look routed correctly.

The FPU VSV is located in the center of the three on the inner fender. the line in question runs from the outside (closest to fender) to the lower right of the triple fiting that is located near the top of the plenum towards the rear.