Car near dies and high fuel pressure

[Boddie]

So my car has always ran rich at idle and during normal driving. It fixed mostly after I changed the O2 sensor, but it is starting to act up again. Sometimes while just driving, it will just start to die. It is not in between shifts like what happens when venting to the atmosphere (I am not doing that btw), and there are no boost leaks or anything.

When it starts to die (in any gear / RPM) RPMs quickly drop, and when I give it gas to try to get the car back it studders violently and sometimes revs at random rpms as if it is hitting fuel cut at random places. When this intermittently occurs, it will sometimes blow out black smoke for a second, backfire, and just go nuts. Sometimes it does not happen for a week, and other times it will happen like 6 times on a quick run to the grocery store.

I do know that there is a fuel pump rewire done (done by previous owner). I do not know if the stock fuel pump is in the car or not. I know that stock 1G turbo m/t car should have idle fuel pressure at around 38 psi and it for some reason is sitting at 66 psi. On a possibly related note, I noticed a long time ago that the car will not rev passed 4500 RPMs while in neutral (not that there is a purpose to this it just seems kinda of strange), it acts like it is hitting a rev limiter.

Any ideas would be great?

Thank you in advance!

 

[Ej20racer]

If you trust your fuel pressure gauge, I'd start there. The high fuel pressure is most likely the source of your problems. The only possibilities for that high of fp at idle would be a bad regulator or a restriction in the return line. The pump is going to push as much as it can all the time and the regulator vents what isn't needed back to the tank. Overly high fp would cause your ecu to pull as much fuel as possible (max negative fuel trim), and if that's not enough for your car to run right you'll see the symptoms.

 

[Tyeler18]

You definitely need to turn the fuel pressure back down. Adjust your FPR back down to 37psi and start there. At 66psi base you'd be maxing that fuel pump out bad at very low amounts of boost, not to mention how insanely rich it would be, like stated above the ECU can't even compensate with fuel trims for that much fuel.

 

[Ej20racer]

I assumed the OP had a factory regulator. If its adjustable, turn it down! Also if it's a cheap one, double check the regulator's gauge with a regular fuel pressure gauge.

 

[Boddie]

It is factory FPR, so I cannot adjust it. Is there a faq on how to check the FPR and/or how to check the return line for restrictions?

 

[Tyeler18]

How are you checking fuel pressure then?

 

[Boddie]

I took it to a friend with the equipment to do it for me while I was at work.

 

[Tyeler18]

Can you ask him where he was checking from? If he just put a tester into the fuel filter and tested there he would be testing the max output of the pump. Which 66lbs sounds about right.

 

[Boddie]

I have a question regarding vacuum lines that may be for the stock fuel pressure. The person I had checking the pressure noticed that a vacuum line had been cut, and it seems to be negating the fpr. He said with this it is always stuck at over 50psi. I have put up a picture of the vacuum line below:

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If this is causing my issue, does anyone know where the other end of this vaccum line connects? Or if there is a specific line I should tee off of for this source?

Thank you in advance!

 

[Boddie]

According to this post, it looks like people normally tee off of the fuel pressure regulator vacuum source. In the case of my car, it looks like the previous owner just hijacked the line entirely for the boost gauge and blocked off the vacuum source for the fpr. I just wanted to make sure I understand all this correctly, and that this is the line for that.

 

[Tyeler18]

Is there a vacuum line at all coming off your FPR? Or is it a bare nipple?