Is my adjustable fuel pressure regulator bad

stevesLX

Member
Nov 12, 2006
373
0
16
cincinnati
O.k. guys last week I took the car out for a drive and got on the hywy and as soon as I got into 3rd gear and got up to 5000 RPMs the car started bucking and missing so I got out of it. I had the control module checked out and it was bad so I replaced it. The plug wires are only about a month old. I looked at those in the dark and nothing is arcing. I put my factory coil back in and it still did it. So I continued to drive the car and it would only do this up at the top end and primarily in 3rd or 4th gear. So today I go to leave work and I take off and as soon asx I get into 2nd gear it starts backfiring and wouldn't stop unless I let off the gas and drove with the flow of traffic. As soon as I gave it any amount of gas in 2nd 3rd 4th or 5th it would immediately start backfiring and bucking and no power. So when I got home I disconnected my return line which I beleive is the one without the shrader valve and I plugged it off with a large heater hose and a hose clamp because thats all I had and I stuck a half inch ratchet end in the other side of the hose and I grounded the fuel pump test point and had someone turn the key and my guage on my BBk AFPR shot up to 80PSI and then very slowly drooped off after we turned the key back. I have the pressure adjusted to be at 38 PSI. So should it have done this? I dont know whatelse to do or what can be causing all this. I know if I start the car and diconnect my vacum to thee AFPR and rev up the motor and hold the rpms up the pressure guage will jump back and forth up and down and sometimes it willstay up. I also replaced the fuel filter. The fuel pump is only about 4 months old. Its a 255.
 
it should pull a steady reading with the engine idling....

however, just swap the stock piece back in, and try that. Why do you have an adj piece, then set it to stock settings??

As well, the computer will adjust for the adj fuel pressure regulator if you try and dial in more fuel than the factory setting....the computer will compensate and you'll be right back to square one. Stock piece for the win unless you have a tune.
 
If i'm reading your post correctly, you blocked off the return line correct? I think the fuel pressure regulates the constant pressure in the line by allowing fuel to flow back through the return when it sees it above a threshold. By pluggging the return line you didn't allow the fuel to return to the tank so it just built up pressure.