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Rb20det Rough Idle

91rb20s13
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91rb20s13 Newbie

91rb20s13

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Well I've been searching for a few months (yes i know about the search feature thanks) now for a solution to this without wanting to spend 1k ish on nistune+install+tuning and its gotten pretty bad after going from having the air filter just run directly off the maf in the engine bay, i added the Cold Air intake i fabed up this weekend which goes down next to the IC piping into the Wheel Well. i don't know if this is causing the problem or amplifying an existing problem. I also recently added the FMIC + BOV (Recirculated) this past week.

First off here's what i'm working with:

Stock Internally RB20DET

Stock ECU

Stock Turbo running 10psi

Stock Injectors and Coils that came with the car

Walbro 255lph in-tank fuel pump

FMIC w/ 2.5in piping

HKS SSVQ (Recirculated) (This BOV is giving me the compressor surge spuddering at low boost)

Custom CAI using a Cone Filter on 3in piping and Stock RB20DET MAF

APEXi N1 Catback 3in

Spec Stage 1 Clutch

Competition Lightweight Flywheel (was told this could be affecting the decel and causing the RPMs to fall too fast)

I have a Z32 MAF and Nismo FPR that i need to install, would these help? I also put some fuel injector cleaner in my last fill up thinking the injectors might be cloged but didnt help any.

Problem:

The car runs perfectly fine and pulls hard under boost. During idle it fluctuates radically between 500 and 900RPM ... tries to fall on its face like its got a big cammed v8 in it or something, it leans out during this from 14.1 to +18.0. also when i push in the clutch to stop once its warmed up, it drops the RPMs down to 5-600 and almost dies unless i heel toe the gas and brake to keep it up. when its cool it stops at around 1100, then levels off to its usual 850ish idle.

i'm aware it could be several things and i'm willing to look into them... like cleaning the AAC Valve and whatnot... just need to know where i should start. Prior to the FMIC and CAI it was running fine. Could it possibly need a tune that bad due to colder intake air? Should i change the stock spark plugs? could it be the coils going out? it doesn't misfire in boost or studder...

I figured i'd come ask you guys in AU since you have more experience with the RB20 then most of the guys here in the states.

Edited by 91rb20s13
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91rb20s13 Newbie

91rb20s13

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Any chance you damaged the maf while installing you cai? Sounds like you maf signal is dropping in and out. Is your bov open below 5" of vacuum? If no throw it in the bin and use the STD one.

well i accidentally pushed in that wire mess on the filter side of it... but that has nothing to do with the actual sensor that i could see other than protecting the sensor from objects that got through the filter... but anything small enough to get through that would pass through the mesh anyways... i just removed the screen and went with it.

also i noticed previously that there was a line that went into the center of my previous filter... that came from a hard lines hose... something about oil IIRC... that may be causing a vacuum leak... i'll try to cap it and see. not sure if that's supposed to be going to a catch can or what.

See here the vac line coming out of the fliter.... thats no longer connected to anything on my new filter as there's no hole for it. this is an old pic prior to the FMIC and new BOV... but the filter would be the same. i can get some pics in the morning of what it looks like now.

l_1147cf7e158143c3a281284b7e8d2b05.jpg

Edited by 91rb20s13
91rb20s13 Newbie

91rb20s13

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ok well... i drilled a hole for the vac hose going in my new filter and plugged it in.... all is normal.... not sure what that vac line is supposed to go to... possibly the AC that used to be in the car with the KA... who knows. at least its running like a champ.

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