I am wondering about the proper functionality of the fuel pressure regulator. I have a 1 st gen 4runner with a 3.4l from a 97 taco in it. Finally got the truck running and it idles perfectly. However when I give it gas it stumbles and falls on it face. It won't accelerate at all. When I pinch the fuel return line though the truck runs much better and accelerates as it should. Ia getting codes for multiple random misfires and misfires on almost all cylinders. My next step is replacing the fuel pressure regulator and fuel filter. I know my fuel pump is good because I just replaced it a few months ago. Any ideas?
Thank you all

 

Did you replace the filter, too? A partly clogged filter, and/or fuel lines, especially at corners, where "stuff" sticks, will cause low volume of flow. Pressure is good, but when the engine needs a higher volume flow, it's not available.

The regulator, with the vacuum line removed, should have 38-44 PSI fuel pressure. With the vacuum line attached, it should be 33-38 PSI, I believe the Book specifies.

I think the volume should be .5 quarts per 1 min of flow. Connect a clear piece of tubing to the return line of the pressure regulator, and put it in a graduated container. Use the B+ and Fp contacts in the test connector to make the fuel pump run, with the key ON. Measure the flow rate. It's not just fuel pressure that matters, but volume as well.

Good luck!
Pat☺

 

Sweet, thank you for the actually informative reply. The Fuel filter and pump are new. However they sat for 7 months while I worked on my swap. So old fuel might have messed the filter up. I will replace the filter again and try the fuel flow idea.

 

Here are the specs and instructions from Toyota, mind you it is 01-2002 model year, and the 97 had different injectors but believe the specs are the same, and same procedure. I would think P0300 codes would be spark, timing or injectors, but the old style 5vz-Fe injectors don't fail often, and it wouldn't hurt to test the fuel pressure, but I would think low fuel pressure would show up as a P0171, but the OBDII can surprise us if we don't look at live data.

http://www.teamtoyota4x4.org/archivi...fuepum/ovi.pdf

 

I am having the this same issue with an 01, what did you find out? I have a new fuel pump, fuel filter, and spark plugs.