Hi guys Ive been a long time reader but recently signed up when I hit a wall and just cant get past it.
I own a 94 5.0 5 speed with ~110k miles on it. Ive owned it for a half a year, really decent car for the price. I had a local shop put in 3.73s, it also has an X pipe with cat delete, and a local shop made a cold air intake for it, which turned out to be suprisingly decent quality.
About 3 weeks after I got the X pipe I started experiencing a dramatic power loss above 3k rpm (it just wont rev) and sometimes the car has trouble starting. I asked around if this had to do with the cat delete but everyone I asked said that in no way would dramatically affect the performance of the car. By dramatic power loss I mean my brothers bone stock 96 4.6L automatic car flies away from my car.
I used my dad's code scanner and I get nothing. It all checks out. I had the fuel injectors cleaned when I first got the car so I dont think that is the problem (although I havent ruled it out). I used my Chilton's manual and followed the procedure for checking the fuel pressure. The pump only puts out around 30-31 psi and holds at that. The manual says it should be putting out about 40 psi when doing this test. I replaced the fuel pressure regulator, but same deal, still 30-31 psi. Ive been told that when the fuel pumps go bad in these cars they just go dead and the car wont start period, I dont know if that is true or not. I also checked all the fuel lines as best I could with the car jacked up, no kinks or smashed lines as far as I can see.
So what are some other possibilities?
Could the pump just be bad?
Is it possible there is a vacuum leak? The guide said I could try disconnecting the vacuum line and plugging it (the one that controls the regulator), then buying a hand pump and seeing if the psi comes up to where it should. I dont own a hand pump but is it worth my time to buy one?
Could the fuel rail be clogged? Could an injector be clogged and blocking flow to the other injectors? (I have no knowledge of what the fuel does between going into the rail and the point where I am testing it).
Does computer control have anything to do with it? It seems to me like the pump should just provide 40 psi then the regulator adjusts how much regardless of the computer.
Any info would be appreciated because I am really stuck! The car was really quick for a while there and now it is just a dog
---Updated---
HISSIN thanks for the info
I ran the fuel pressure test again, making sure I had the vacuum line unplugged and the ports plugged. 41psi at WOT. No the car does not ping, I checked the timing at idle and it is at ~10 degrees advanced.
My brother reccomended replacing the coil, which I did and it seems to rev better, but the power still isnt there.
I used my brother's G-Tech on the car on as flat of ground as I could find and the car does 0-60 in 9 secs, stock is like 6.5? (just as a frame of reference Im not implying I should be able to drive the car that quick)
I already replaced the fuel filter (one of the first things I did).
Tonight I ran a compression test. Every cylinder was between 126-134. That seems fine to me. I guess this narrows it down to either a slipping clutch or a computer problem?
I own a 94 5.0 5 speed with ~110k miles on it. Ive owned it for a half a year, really decent car for the price. I had a local shop put in 3.73s, it also has an X pipe with cat delete, and a local shop made a cold air intake for it, which turned out to be suprisingly decent quality.
About 3 weeks after I got the X pipe I started experiencing a dramatic power loss above 3k rpm (it just wont rev) and sometimes the car has trouble starting. I asked around if this had to do with the cat delete but everyone I asked said that in no way would dramatically affect the performance of the car. By dramatic power loss I mean my brothers bone stock 96 4.6L automatic car flies away from my car.
I used my dad's code scanner and I get nothing. It all checks out. I had the fuel injectors cleaned when I first got the car so I dont think that is the problem (although I havent ruled it out). I used my Chilton's manual and followed the procedure for checking the fuel pressure. The pump only puts out around 30-31 psi and holds at that. The manual says it should be putting out about 40 psi when doing this test. I replaced the fuel pressure regulator, but same deal, still 30-31 psi. Ive been told that when the fuel pumps go bad in these cars they just go dead and the car wont start period, I dont know if that is true or not. I also checked all the fuel lines as best I could with the car jacked up, no kinks or smashed lines as far as I can see.
So what are some other possibilities?
Could the pump just be bad?
Is it possible there is a vacuum leak? The guide said I could try disconnecting the vacuum line and plugging it (the one that controls the regulator), then buying a hand pump and seeing if the psi comes up to where it should. I dont own a hand pump but is it worth my time to buy one?
Could the fuel rail be clogged? Could an injector be clogged and blocking flow to the other injectors? (I have no knowledge of what the fuel does between going into the rail and the point where I am testing it).
Does computer control have anything to do with it? It seems to me like the pump should just provide 40 psi then the regulator adjusts how much regardless of the computer.
Any info would be appreciated because I am really stuck! The car was really quick for a while there and now it is just a dog
---Updated---
HISSIN thanks for the info
I ran the fuel pressure test again, making sure I had the vacuum line unplugged and the ports plugged. 41psi at WOT. No the car does not ping, I checked the timing at idle and it is at ~10 degrees advanced.
My brother reccomended replacing the coil, which I did and it seems to rev better, but the power still isnt there.
I used my brother's G-Tech on the car on as flat of ground as I could find and the car does 0-60 in 9 secs, stock is like 6.5? (just as a frame of reference Im not implying I should be able to drive the car that quick)
I already replaced the fuel filter (one of the first things I did).
Tonight I ran a compression test. Every cylinder was between 126-134. That seems fine to me. I guess this narrows it down to either a slipping clutch or a computer problem?
WELCOME TO THE SITE 
WIZARD 
