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Fuel Pressure + Hunting Idle Issues

big fat paulie

By big fat paulie,
in Engines & Forced Induction

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big fat paulie Contributor

big fat paulie

Posted
Posted (edited)

Hi there people more knowledgeable than me.

New to the skyline world but been around cars all my life.

I have not long ago purchased an R33 GTST series 1 with the following mods.

- 3inch turbo back exhaust

- K&N air filter in stock airbox

- yellow jacket coil packs

- nismo fuel pressure reg

- walbro 500hp intank fuel pump

Car is otherwise stock (including boost pressure and BOV).

My car is running like shit. Rich as all hell. Massive pops on gear change/overrun, black soot all over the rear bar and getting ~300km to a tank on the highway.

My fuel pressure seems to be way too high. About 60 psi at idle.

What should it be and how can I adjust it?

When I install a FMIC and up the boost (as we all know this will happen sooner or later) will I need to adjust it again?

Also the car occasionally hunts at idle. (600 to 900 rpm). I am guessing its not a vac leak as it doesn't do it all the time.

Will fixing the fuel pressure problem fix the occasional hunting?

Will fixing the fuel pressure fix the economy issues?

Will an ECU reset also assist?

Anything else i should check?

Thanks very much for your time.

Paul.

Edited by big fat paulie
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Bsa Mentor

Bsa

Posted
Posted

Fuel pressure I normally set around 38 to 40 psi with vac line removed I have no problems whit that pressure. You can't put any more then 10 pound boost with stock computer. Your o2 sensor may be dead that will cause bad fuel economy.

TerribleOne Enthusiast

TerribleOne

Posted
Posted

Try re soldering the joints in the AFM and cleaning it with electrical contact cleaner, my old R33 had similar symptoms and doing that got it running sweet. Also o2 sensor like the guy above me said, easy to replace and cheap too. Probably worth doing it regardless.

big fat paulie Contributor

big fat paulie

Posted
  • Author
Posted

So i lowered my fuel pressure as per the gauge to about 45 psi.... Car would hardly start, spluttered when gave some throttle.

im starting to think the gauge is wrong.

How should a fuel pressure gauge be set up.

My sensor is between the fuel filter and the FPR, Is this right?

Bsa Mentor

Bsa

Posted
Posted (edited)

Put a stock reg on there atleast you can rule out the fpr there is no need for it unless your trying to get more out of the injectors anyway in which you case stock is best. Also change your plugs they are most likely fouled from running rich. Has the car had a remap or nistune? If your located near central coast I can help you sort it out

Edited by Bsa
SargeRX8 Grand Master

SargeRX8

Posted
Posted

Songs too rich, fuel burning in the exhaust, black soon, rough idle due over fueling. get a stock fpr back on it. It will run a tad higher than stock sure to the increased flow from the pump but it will be fine. Are you fouling plugs?

89CAL Grand Master

89CAL

Posted
Posted

Songs too rich, fuel burning in the exhaust, black soon, rough idle due over fueling. get a stock fpr back on it. It will run a tad higher than stock sure to the increased flow from the pump but it will be fine. Are you fouling plugs?

My god are you drunk? Spelling is all over the shop

Changing the FPR settings doesnt increase the flow from the pump, it changes the restriction to flow from the pump. Your pump flows the same, the FPR changes the pressure (How much fuel is allowed to get through)

Guage sounds like it's in the right spot to read the fuel pressure correctly. Fuel pressure should be the same between the fuel filter and FPR. Unless your gauge is faulty as suggested?

SargeRX8 Grand Master

SargeRX8

Posted
Posted

My god are you drunk? Spelling is all over the shop

Changing the FPR settings doesnt increase the flow from the pump, it changes the restriction to flow from the pump. Your pump flows the same, the FPR changes the pressure (How much fuel is allowed to get through)

Guage sounds like it's in the right spot to read the fuel pressure correctly. Fuel pressure should be the same between the fuel filter and FPR. Unless your gauge is faulty as suggested?

Its a pain in the arse writing off the Galaxy S2, the swype keyboard doesn't always get it right haha. But that is what I meant. Not flow, but pressure. Due to upgrading his fuel pump, the pressure will be above stock but still within a safe limit to ensure the car runs fine.

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