Another Rb25 Misfire Topic

[fmlycar]

Tried a known working z32 afm. No change

[Ben C34]

Check fuel pressure.

So you pressure tested for boost leaks?

[Dose Pipe Sutututu]

Jam a wideband on the exhaust

[fmlycar]

Think I may have found my gremlin. Was testing fuel pressure again and had 50psi at idle, pulled vac line for reg and fuel pressure didn't change. Just ordered a nismo reg and will fit that when it gets here. This would explain why it's been so rich and fouling plugs.

[lcxu105]

I currently have the same problem with mine. Was fine on dyno this morning then on the way home developed a miss fire at 4500rpm. Gappef plugs down from .7 to .5 only lowered the miss in the rpm down to 3500. Made it worse. Going to change the plugs tomorrow. And set to .55mm.

[fmlycar]

I still haven't gotten to the bottom of mine. Still awaiting parts. Mine feels fuel related as I have surging at cruise speeds with constant light load

[lcxu105]

Had problems with fuel as well. Couldn't run more than 18psi boost. Couldn't get enough fuel out of the walbro 460lt pump. Suppect it is sucking down on the bottom of the tank.

[fmlycar]

This was this afternoon driving home from work

[fmlycar]

First 3 plugs are all sooty and black. Fuel pressure seems pretty high both with vac line on and off.

[lcxu105]

Mine where all burning good. Tuner said hose must of fell off somewhere. Boost leak. Couldn't find any off so new set of plugs first the change fuel filter and check out the height of fuel pump in tank. After that. I'm at a loss so it will be going back to tuner if I don't find the problem

[lcxu105]

Mine where all burning good. Tuner said hose must of fell off somewhere. Boost leak. Couldn't find any off so new set of plugs first the change fuel filter and check out the height of fuel pump in tank. After that. I'm at a loss so it will be going back to tuner if I don't find the problem

[fmlycar]

Well I think nearly 50psi at idle is a wee bit too much and not helping my cause. Once the new fuel reg gets here, I'll set it at 42psi no vac and see if that helps.

[XRATED]

What was rail pressure when it was tuned?

[fmlycar]

Was tuned at standard rail pressure. It's going for a retune end of month so if it needs to be bumped up or pulled back they can do it then.

[lcxu105]

Found my problem this arvo. Changed plugs didn't do anything. Pulled fuel filter out. (Aeroflow reusable one ) stainless steel screen was blocked. Changed it from 80m to 30 m took for a run and was fine. Will pull the tank on the weekend and clean it out.

[fmlycar]

Glad you found yours. I'm still waiting on fuel reg and fuel pump so I can set base pressure and make sure it's not running out up top.

Edited August 11, 2015 by fmlycar

[fmlycar]

Pretty sure duty cycle shouldn't be that high on 550cc squirters and 18psi on a Td06 only making 240rwkw.

Looks like the new fuel pump is required anyway

Edited August 11, 2015 by fmlycar

[lcxu105]

Will be up there. 550cc injectors in mine where just about maxed out.

[fmlycar]

Nah that's way too high. 550cc should be good for over 300kw on pump. Before I was having issues I would see values around 67% even with spikes of 2-3 psi in boost. Will fit new bosch pump when it arrives and report back.

Edited August 11, 2015 by fmlycar

[Ben C34]

Boost leak.