S13 RB25 running rich at idle

[KyleT]

Hey, we finally got my buddies s13 rb25 going and its running very rich at idle. The wideband starts around 15:1 and after about 30 seconds is at around 10:1, which is very rich for idle. Now when you try and rev it up it only will rev to around 3k rpm and seems like its hitting a revlimiter/bogging out. When you try and rev the car up the wideband goes full lean and comes back down to around 10:1 when the car revs down back to idle.

We tried unplugging the maf and the car dies, so I think the maf is working. But the car has a z32 maf which came with his motor swap. So Im thinking it should be wired up correctly since it ran before. Any way I can check?

Car has an aftermarket fuel pump and adjustable fuel pressure regulator which is set at right about 43.

Just did a boost leak test and didnt find any major leaks up to 20psi. Created a vacuum leak and the car doesnt run as rich(around 13:1) but still leans out under throttle. Basically im looking for some help at what to check next.

Forgot to mention the car has a greddy plenum and a q45 throttle body and the iac/aac has been removed.

[RRRRB]

is a z32 MAF sensor even compatible with a stock RB computer? i bet thats your problem

[Carl H]

^ dis guy.

need a stock maf, im surprised it even runs at all as a z maf normally leans a motor way out.

[KyleT]

Thats what I wasnt sure of. I thought I read somewhere that the z32 maf will work with the stock computer but thats most likely the problem.

Now is the correct maf for an rb25det s2 the pink labeled e60 maf? Will any others work? Anything I can find at a junkyard? Or is the pink e60 the only one?

[DA 240]

I thought I read somewhere that the z32 maf will work with the stock computer but thats most likely the problem.

Well the person that posted that most likely was running a SAFC along with their stuck ECU.

[KyleT]

Got the correct maf and wired it up correctly. Car runs alot better and revs up fully now. Wideband still drops down to about 10:1 after about 20 seconds, and the car takes a while to start. air/fuel ratio goes a little leaner when the car is revved up but comes back to 10:1 pretty quickly.

o2 sensor is brand new. Re gapped spark plugs to spec. Boost leak test check out ok.

Still stumped why it runs so rich at idle.

[RRRRB]

whats the fuel pressure?

[KyleT]

45psi on an aeromotive fpr. Tried turning it down a little and it made no difference.

[Carl H]

check for codes.

[KyleT]

If this is the right guide to read codes, we already tried it. http://www.skylinesaustralia.com/forums ... read-them/

There are no wires running to the pins in the connector on his car that the guide says to jump.


And I dont see and potentiometer screw or leds on the ecu, but I think thats only for series 1.

[Carl H]

you have to wire in the consult port as well as the chk pin.
mil needs to be connected for the codes to flash thru.

[KyleT]

Drove the car around for a while today. It idles a little better, but still on the rich side. Air/fuel ratio seems to jump around alot at idle. It will stay around 14-15 then all of a sudden its back down to 12-13 then sometimes goes up to 16. Think this may have to so with the idle going up and down a little.

Driving the car, afrs seem alright, still a little on the rich side and sometimes leaning out under throttle. But when you punch the pedal it sort of bogs and seems like it doesnt want to go and sputters a little bit under boost. It just feels like it has no power. The car doesnt completely fall on its face, it just doesnt pick up and go.

[Carl H]

got BOV?

[KyleT]

Yes, which isnt recirculated. I know its no opening or leaking at idle, I pulled the vacuum line off it so it stays closed and it runs the same. I can see its no opening and there is no air leaking out of it. Its not leaking under boost either, boost leak tested it up to 20psi.

[Carl H]

it may be leaking during cruise, light throttle means high vac which can open it.

[KyleT]

Its not leaking when cruising.

Any idea what the bogging/stuttering under WOT could be? It just feels like it has no power and doesnt boost like it should be. Im going to try and get a video next time.

[opticnerv]

check to make sure your throttle cable isn't sticking on your hood. Happened to my car I took my dremel and cut the section of hood skeleton that was squashing the throttle cable. If thats your problem you'll see the markings on the hood

[KyleT]

check to make sure your throttle cable isn't sticking on your hood. Happened to my car I took my dremel and cut the section of hood skeleton that was squashing the throttle cable. If thats your problem you'll see the markings on the hood

Thanks, for the tip, but thats not the problem.

He put about 50 miles on the car. The afr's at idle are a little better, but still jump around alot. its around usually 14:1 sometimes will go down to 12:1 and then sometimes jumps back up to like 16:1.

Still breaks up/stutters under boost, but I think it might be from lack of tune.

[KyleT]

Anyone know what could cause the air fuel ratio to jump around so much at idle? It goes from 10:1 all the way up to 16:1 and never stays at a consistent ratio.

[Orthank]

What are the other modes done to the engine. The greddy plenum and 90mm intake are enough to make a stock computer not act normal.

[KyleT]

Rb25 series 2
precision 5557 turbo
top mount tubular turbo manifold
full 3" exhaust
fmic and piping
greddy intake manifold plenum
q45 throttle body

Also have aem ems waiting to be installed, but thought we could get the car running somewhat decent before we hook it up.

[KyleT]

forgot to mention car also has

deatschwerks dw300 fuel pump
aeromotive adjustable fpr

[Carl H]

its kinda silly to do all that and assume that the car would actually run somewhat normally.
also boosting on paltry 370cc injectors with no tune on a big turbo is asking for damage.