Rb20det Has 2x Fpr's?

[kitto]

***Apologies for the long post***

RB20 Gurus please read.

Hello all, i would post up photos to show you exactly what i'm talking about but i can't.

Now we all know that your EFI engine has a fuel pressure regulator, but my RB20 has two! Yes two and i have seen quite a few other RB20's with two fitted as well. But alot also only have one.

The main one is obviously the one at the front of the engine, its a normal Nissan FPR, and it gets it vac/boost signal from the inlet plenum itself.

The other one i am talking about is fitted at the rear of the fuel rail, it looks identical to the other one except this one gets its vac/boost signal from the idle air control valve line, or in other words before the throttle body.

If you know your RB20's you'll know what i'm talking about. The odd thing is, is fuel pressure from the tank comes into this FPR at the rear and goes through it, then into the rail, feeds the injectors and then the remaining fuel flows into the 'main' FPR as per normal.

My question is, WTF is it doing there and can i remove it?

Now the reason i ask, can it cause a missfire, its well because my car has a bad missfire! NO i DO NOT think its coil packs. Why? - Because i'm running EL/EF/AU Falcon coil packs, now these coil packs are second hand and so are the leads.

Plugs are brand new NGK Coppers BCPR6ES gapped at .8mm.

Symptoms;

Car starts and runs fine at 15 degrees BTDC (normal ignition timing), come on full boost in second and as we get to 4500 - 5000RPM the engine will basically cut completely out at full throttle, however if i keep throttle on at about 1/8 it will cough and splutter until around 6,000 and then clean up and reach limiter.

The engine will also occasionally miss at idle, but this is where it gets interesting, if i hold the throttle on around the 2KRPM mark with no load it will miss fire like crazy, not cough and splutter, just miss and pop, yes its running on 6cyl.

Now keeping this in mind, the engine still at 2KRPM no load... Now if i retard the timing completely back to 0 degrees the miss goes away completely. No i havn't driven it at 0 degrees timing and i'm not going to. If i advance the timing the miss gets a lot worse.

Interesting huh?

Mods to car; (R31 Skyline BTW)

FMIC

Catch can inline

No exhaust at the moment - just dump

VG30 turbo - not that it matters - Factory 10PSI

AU falcon coil packs

Bosch 040

Non - remapped ECU

Runs on BP Ultimate

Things i have tried to rectify problem;

Cleaned AFM that much you could eat off it

Timing

Checked plugs

Changed CAS to a known working one - no difference what so ever

Made sure it wasn't surging

Checked for vac/boost leaks

Checked and clean all ignition connections

Compression is OK

Things i have yet to try that are possible;

Change leads - doubtful cause

Change coil pack - doubtful cause

Change ignitor pack

Change FPR - i have a SARD one going in

Change plug gap

Change AFM just to be anal

Oxy sensor wont cause a fault like this as its only used in closed loop

Run injector cleaner

Probably a few more as well

Now the reason i say that it wont be the coil pack or leads is because i highly doubt that it will miss the way it is at 2KRPM with NO load! The engine also did the exact same thing with the original coil packs so i doubt its the newer packs.

If you have any idea where i should look please let me know, i know its not a common miss fire fault normally caused by coil packs. I would like to have it fixed before i throw it on the dyno, it could take hours to find the fault.

I'd really like to put dyno time/money towards a remap.

I'd look forward to your replys. Thanks!!!

[Bumblebee]

i think u will find that it is possibly a pulse resonator thingy majig

i seen em b4 as well, and they look like regs

dunno... weird

[The Dan]

Leave the FPR there.

Change your fuel filter

Once you have put a new filter on have the injectors cleaned by a professional by removing them. Don't just run an injector cleaner through them.

Sounds like you might have a faulty 02 sensor also.

And FYI, Do you have any idea how many EF/EL coil packs I have replaced in my time? - when I was working for a RACQ workshop we were doing one a day for the 3 months I was there and I can't even remember how many I've done prior or after that.

[kitto]

Leave the FPR there.

Change your fuel filter

Once you have put a new filter on have the injectors cleaned by a professional by removing them. Don't just run an injector cleaner through them.

Sounds like you might have a faulty 02 sensor also.

And FYI, Do you have any idea how many EF/EL coil packs I have replaced in my time? - when I was working for a RACQ workshop we were doing one a day for the 3 months I was there and I can't even remember how many I've done prior or after that.

Hey matey, cheers for the reply. Fuel filter is brand new. O2 sensor is shagged i'm sure of it, but i'm positive it wont cause a fault like this. Youv'e really replaced that many falcon coil packs? Were they completely stuff or breaking down? Did they actually break down on idle?

[kitto]

Hey Guys - UPDATE time.

Ok so just now i have changed several things and they have made no difference what so ever.

I have changed/checked

- AFM

- Checked for leaks again

- Regapped plugs down to .7mm

- Changed CAS to another one again and no difference

- Put a front pipe on and it has no difference, the miss is now more noticable though

- Checked all leads and ignition connections again

- Installed my SARD FPR - Fuel pressure at idle is set at 38PSI - A tad above Factory

Factory fuel pressure at idle is 2.5kg/cm = 35.558PSI, so i upped it a little. I also played with the pressure up and down - no difference.

Tomorrow i'm going to get some custom leads and try them.

Only other two things i can think of would be coil pack and ignitor pack.

[The Dan]

Hey matey, cheers for the reply. Fuel filter is brand new. O2 sensor is shagged i'm sure of it, but i'm positive it wont cause a fault like this. Youv'e really replaced that many falcon coil packs? Were they completely stuff or breaking down? Did they actually break down on idle?

Yeah, the o2 sensor can cause the missfire at 2k as it enters closed loop mode then.

Yes I have replaced that many. They were always just stuffed. Never 'on their way out', one minute the car would be running, next minute...stopped.

We would sometimes get them come in with distributor failure, replace the distributor, car would run fine for ten minutes then the coil pack would die. So after doing 20 or so like that we just used to do coil pack and dizzy at the same time.

What about the injectors? Have you had them cleaned professionally? Adding or subtracting fuel pressure will make a broad adjustment to all injectors fuel delivery, not just one. You sound like you are pretty much covering all bases though. Keep trying, you'll get it eventually

[kitto]

Hey mate, well next up is new leads and i'll borrow a known working set of falcon coil packs. I'm not forking out $100 when i dont have to straight away.

No i havn't had the injectors cleaned. Its around the $150 mark. And they're only stock items. That will happen last if i can't find the problem. Car will be thrown on the dyno before i clean the injectors i think.

I'm thinking electrical, as i had it idling just before and it was breaking down, as in dropping a cylinder and coming back again. Fuel wont cause that issue. So this is making me think its coil packs and or leads.

02 Sensor will be replaced, but i thought because its a closed loop O2 sensor, the ECU only reads the signal when cruising or decelerating and decides if its running too rich?

Anyone know what a Silver top RB20 O2 sensor is worth? They are different to an RB30 one.

[MBS206]

Get another known working ECU, and test it.

Check the injector loom wiring. (Not just the plugs, but the actual wiring...)

[kitto]

I've checked all that, all seems fine.

I thought about checking the ECU.

Am i able to use one that has been remapped?

[daisu]

...around the 2KRPM mark with no load it will miss fire

02 Sensor will be replaced, but i thought because its a closed loop O2 sensor, the ECU only reads the signal when cruising or decelerating and decides if its running too rich?

Yeah, ECU reads the O2 sensor when under light loads (cruising and idling). Since there is little/no load when you hold the throttle at 2krpm in neutral, do you not think the ECU will be trying to read the O2 sensor then?

As for ECU, you can only use a remapped ECU if it has been remapped to suit modifications similar to yours. (ie if the donor car has any modifications such as larger AFM, cams, injectors, diff compression pistons etc then it will not work).

My guess is that there is a leak on the inlet/intercooler piping, as I had a similar problem to this which disappeared when I replaced my front mount and pipes with a side mount and new pipes.

[kitto]

Finding a new O2 sensor isn't easy!!!

I am borrowing a mates remapped ECU, the setups are almost identical so it should be alright.

The only way i could rule out a leak in the cooler would be to hook the afm straight up to the T/B and see how it runs.

My new leads will be made up tomorrow, i'll have a play then.

[VLTWagz]

I know this is an old thread but my car has pretty much the EXACT same symptoms: http://www.skylinesaustralia.com/forums/Rb...pm-t315539.html

Did you find out what the cause was?