If your fuel pressure has been checked and still having acceleration issues than suggest cleaning the MAF sensor.

If cleaning MAF sensor does not work you may have a bad MAP sensor for UTEC.

 

Its the same FPR thats been in there since the turbo kit went in. I never questioned whether it was aftermarket or not...but it's been running fine for years unless the FPR is just now going bad. How do i test the fuel pressure under load and what am i looking for. Like what is a good reading and what is a bad one? Does bad pressure mean bad FPR?

 

found the issue, took the fuel pump out and the rubber grommet that sits on the top of the pump where it slides into the top of the housing has deteriorated. this explains the intermittent issues also, and why it ran better when on a full tank. Problem is now...i cant find the part number anywhere....anyone have any ideas? searching here shows people with the same issue inlcuding pictures....but i cant find part numbers anywhere.



edit: here is a picture stolen from the other thread. that grommett slides on to the shaft of the pump.

 

Okay so infiniti claims there is no part number for the rubber fuel pump grommet...and told me i would need to buy the entire 413 dollar assembly which is "likely to include" the grommet...way to go dealership.

Anyway after searching online i found a few people who shared this problem...and one guy found a Mitsubishi Evo rubber fuel tank grommet and gave it a try, said it fits fine and it fixed the fuel pressure issue. I've ordered a couple of them and im going to give it a try.

Mitsubishi part number: mr431121

 

So i put the new pump in today, with the mitsubishi grommet....and not ONE bit of change. The car still runs exactly like it did before...really choppy and rough idle...still not getting fuel to the motor apparently

 

We hooked the car to a live data scan tool and it shows its trying add 20% fuel at idle....which its obviously not getting. When i unplug the pump with the car off....hardly any fuel comes out...isn't it supposed to squirt out pretty good?

How do i test the pressure at the fuel rail without cutting the fuel line? seems only other way is to buy a 60-100 dollar adapter which is pretty ridiculous.

The spark plugs are brand new, that was the first thing i did when this problem started.

I havent spent much time hunting down vacuum leaks since it's showing its starved of fuel, if it was a vacuum leak, wouldnt it run more rich?

MAF has been cleaned more then once too.

 

I guess this wasn't the problem...
a boost indexed FPR raises the fuel pressure with the boost pressure to maintain the desired fuel pressure
ie 50psi of fuel pressure working against 10 psig of boost = only 40psi
some are linear to make tuning easier and some are variably proportionate depending on spray pattern and engine needs. Avoid the bandaid "Fuel Pressure Risers" that try to allow you to boost with out tuning (usually up to about 7psig)

to test you need a temporary or permanent fuel pressure gauge and just watch for it to rise as boost rises

 

so i found out the does NOT have an aftermarket fuel regulator, i guess its handled by the stock fuel assembly...so the FPR isnt the problem.

I just got done hooking it up to another live data scan tool and fuel trims were 9 and 3 percent....which i was told is fine. Also let the car run for a while and unbolted the fuel line at the damper and it squirted pretty good....which leads me to think pressure is fine, at least up until that point.

I just tried an ECU reset but the misfire is still there at idle and while driving. really quite rough. I also tried cleaning the MAF again.

The code reader also showed 2 more codes that were stored...one was p0113(intake air sensor 1) and p0183(fuel temp sensor a)

Any idea if these codes are related to the p0300 and misfires im getting?

I was hoping to be able to read live misfires to narrow down which cyl is the most and how often but the reader wasnt able to.

 

compression showed between 180-165 psi all around.
Plugs replaced
Fuel pump replaced
Long term fuel trims looked acceptable (3 and 9 percent)
Cleaned MAF
Retightend all intake piping clamps(100 times)
Sprayed for vacuum leaks...nothing noticeable.

Car still misfires idle and drives like crap. SES light blinks intermittently when driving it up to speed.

what am i forgetting here?!

 

Have you checked if the FPR is working properly??
You replaced the fuel pump which is completely independent.
Almost would throw out did you check on the exhaust side?
That can cause the car to bog under load trying to pull on the fwy.

 

i can't hear any physical leaks on the exhaust but i haven't messed with the piping...i was thinking a bad catalytic converter could cause this but wouldn't that throw it's own code?

I thought the fuel pump/assembly is what controlled fuel pressure on the stock returnless system, is that incorrect?

 

The issue with our fuel pump assembly. (Mine is an 06 MT) is that you can't replace only the pressure regulator. The whole basket assembly has to get swapped out.
Agreed that if you're still running cats some code should be popping up if there was a change somewhere consistent with the probs ur having.

 

Okay I registered just so I can try to help you out (used to own a g35 swapped it for a turbo car.) First cheapest/free thing would be to clean/replace the O2 sensors, turbos tend to really gunk things up. Your MAF may be reading the correct intake but the O2 sensors are probably not reading the correct amount of exhaust. If that doesn't work I would suggest replacing the spark plug wires. Had a friend who's engine was knocking with all new plugs and new wires fixed the problem.