Hey guys I have an odd question about something I've been troubleshooting for a week or so now. well a couple of questions actually.
99' 4runner base 2.7l 4wd auto

1. I was doing a test on my fuel pressure regulator tonight and noticed that I have no vacuum to the vacuum line connected to it. This is odd because I did a vacuum test with a smoker just the other day and had no leaks.

this leads me to part 2

2. I've been getting terrible gas mileage lately along with a p0420 code. ran diagnostics on o2 sensors and downstream is fluctuating which is indicative of a bad cat, but pressure from the pipe and temp seem to be good. Also my buddy has a camera and looked inside and the cat looked pretty clean. have done vacuum test (held consistent at 20), compression test, and the fuel trims look really good. only getting the p0420 code. I'm kind of reluctant to call it a cat just yet because something had to cause the issue (which is why I though of maybe checking the FPR). replaced o2 sensors anyways because mileage was getting up there and haven't done it yet.

list of things done within past year:
tps
maf
plugs and wires (last week)
air filter
fuel filter (summer 2013)
pcv
coil pack for 1+4

engine seems to be sluggish on low end and getting somewhere between 14 and 16 mpg with highway. but problem is also a little intermittent except for the gas mileage.

I broke down a couple weeks ago and brought it to the dealer. misfires on cylinder 1 +4 replaced coil and found excess carbon buildup on intake valves. cleaned the best they could and it was running better. gas mileage was bad prior to this incident and the p0420 code did not appear until a week or so ago.

anyone have any input on either of these issues? I was under the impression there needed to be vacuum to the fuel pressure regulator so it could control the diaphragm... more vacuum = leaner fuel supply, less vacuum = richer fuel supply. could this be part or all of my issue?

thanks

Did you change out the 02 sensor?
Didn't see that on your list.

They do go bad. It's an electrical part....

yes, sorry both o2 sensors (denso)

plugs and wires are ngk as well.

Funny I had the same question a couple weeks ago when I was doing this testing.
I found out through tons of research and asking people that the Fuel pressure reg. in a 3rz 4cyl gets NO vac. from the intake, that line connected to the intake is only to supply clean filtered air to the FPR. (you could even disconnect it)
The FPR regulates the pressure atmospherically, so as you climb in alt. it leans out the mixture. It's an atmospheric FPR.
It's Not part of your problems

good luck
3rzrunner

interesting.. thanks 3rzrunner!

I wonder where to look to now.