HELP... running really rich

[tuitahi]

Hi all,

I need help diagnosing the cause of my car running so rich.

I have an R33 Gts25t, it had an ARC side mount, splitfire coils, apexi super intake pod, turbotech ball/spring boost valve (set at 9psi), 4000km old Iridium plugs... and made 145kws on the dyno. Everything else is stock.

After fitting an exhaust (split dump/front, catco stainless inside cat, nismo cat back and new o2 sensor) the car put out 185kw on the dyno @ 10psi. (Both runs done on the same day, with a real nice power curve)

Unfortunately, thats where the good news stops... the single run could not be replicated. Every subsequent run (on same day) resulted in the car grossly overfueling at around 4500 - 5500 rpm. It happens on the road and the dyno. The curve on the dyno now runs up to about 140kws then drops right down to ~90kw, then in the last 500rpm it leans right out and nabs 170kw.

Now, the car has been with the mechanic as he is trying to diagnose the problem... a list of what he has tried when I last spoke to him;

-several air flow meters

-several stock computers

-removed boost controller

-looked for boost leak

-nissan diagnostics come back ok

-2 different fuel cut defenders tried (which helped pick up outright power, but the curve stayed the same)

-when I last spoke to him he was going to look at the fuel pressure regulator but said he is stumped and has never witnessed this on a Skyline

He suggests some form of aftermarket management, ie Power FC, to fix the problem. However, even though an aftermarket ecu may sort out the power delivery and power curve... there must still be an inherent problem somewhere. And I don't want to pay for an aftermaket ECU if its something else thats cheaper to fix.

Please let rip on any experiences/suggestions!!!

Thanks in advance,

Drew

[PSI_GTSII]

Wellll...I just had a similar problem with mine...turns out it was just a dodgy plug on the ignitor (Under the rocker cover panel on GTR)

Long shot but worth a try

[tuitahi]

@ PSI_GTSII

Thanks dude, will have a look at the igniter in the morning....

any other suggestions people? I'm dying to see how the car runs with the new exhaust and it tears me up not knowing what's wrong with it.

To put it in perspective, it is running so bad I would get flogged by a VN V6 Commonwhore!!

[nitemare5]

Get a piggyback or a full ecu to get it tuned.

The same thing happened to my friend when he fitted a fmic and turbo back exhaust but with the standard ecu. He then fitted his powerfc, and on the first run it saw a massive dip in power in the 4500rpmish range to around 80rwkw with a maximum figure of 120rwkw. After the tune he gained around 80rwkw in that same 4500rpm range to around 160rwkw with a maximum output of 190 rwkw.

[joh21m]

i had the exact same problem on my rb20, wen i was driving around and gave it full throttle as soon as 5500rpm came up it would feel like i just turned on 5 air conditioners. chucked it on the dyno and exactley same thing you described was happening. no one could tell me what was happening...i also got the 'get a power fc and we can fix it up'.

my problem turned out to be one of my knock sensor plugs was leading to the fuse box..lol. i found a spare plug in the engine bay leading to the ecu, plugged that in and waala, problem fixed.

moral of the story...check your knock sensors!

[tuitahi]

joh21m...

Thanks, will have a look in the morning.

As for aftermarket ecu, it may be my only choice, I knew Skylines ran rich but this seems excesive. If you guys are sure this is normal then I guess the credit card gets a work out!!!

Drew

[siksII]

it is normal at around those revs at 10psi with your mods the ecu will run rich and retard ignition timing, it feel like the car suddenly does not want to rev out, right? i have pfc but when i tried the stock ecu this happened to me too.

try running less boost, until its low enough so u dont hit the r&r point, the car will go better than when running low boost and no power at higher revs as your car is running now.

[fresh]

rich and retard shouldn't see a power drop like that, mine just flattened out quite a bit but still pulled to redline

[tuitahi]

siksII, what you describe is exactly what I got...

I have dropped the boost back to stock and its a little better but I can still feel hesitation at the mentioned rev range. (sometimes its ok, but 85% of the time it thinks about whether or not its going to rev out)

I didn't think rich and retard really became an issue until 11-12 psi, the tuner/mechanic said he's seen similar before but not to this extent, which led him to believe there was something else, he seems content that it just needs a tune now.

Oh well, siksII if the pfc fixed it for you, then I guess its a goer. I assume it totally eliminated the drop?

[siddr20]

Hey drew, just curious to see if you fixed your problem or not??

Might give you a call shortly.. but let me know what happened. .

cheers man

edit: wow you posted this last year. hahhah by bad..

well let me know anyways!!

thanks

Edited October 6, 2006 by siddr20

[R31Nismoid]

rich and retard shouldn't see a power drop like that, mine just flattened out quite a bit but still pulled to redline

every car is different. the amount of R&R is different depending on the airflow etc.

the fuel pressure is a 10min check at the absolute most, so that should be easy to eliminate the Fuel Reg.

You really need an S-AFC or PowerFC on there if you intend to up the boost mate, some people are ok, some arent.

Its luck of the draw but the overfuelling most of the time is the ECU's fault

cheers

[siddr20]

Think i need a tune as well.

2nd gear feels like crap..To many flat spots in the revrange.

Have tried turning the boost down as well. Does help a little, but then my car feels so slow lol..

But i have a feelin i just need a power fc and a tune..