RB20 Misfire in boost

[nsxmatt]

Took on a new project and have been trying to work out a bug. I'm a Honda guy so alot of this is new to me.

92 240 with a rb20. Walbro 255 and a Nismo FPR, RB20 MAF, front mount IC. Car cranks over and spudders, dies. Takes a few tries then it starts but idles rich and runs rich in normal driving. Go into boost at WOT and it feels sluggish then will missfire and buck before making full boost.

Has no a/f gauge and the tach is not converted so it's not accurate. Have added slight fuel pressure which makes the misfire worse which has me thinking it's running too rich. Have to lower the fuel pressure almsot to the point of dying to have any midrange power. Has new plugs gapped correct, maf has been cleaned, all hoses and IC piping has been checked.

Anyone have this problem before or can someone point me in the right direction to check next? I'm going to check the MAF voltage and the TPS, anything else?

[Joe]

check your codes

and for future reference, changing your fuel pressure blindly to the point of stalls is a BAD idea. (no wideband)

[Nissan2367]

My RB25 does the same thing... and has for the last 4 months But i have replaced the MAF, coolant temp sensor, timed it (6-7 times), comp tested, spark plugs, and cleaned the injectors, checked for vacuum leaks, and tested the coils... still does the same thing so if you hear something let me know!!!

[nsxmatt]

check your codes

and for future reference, changing your fuel pressure blindly to the point of stalls is a BAD idea. (no wideband)

Wasn't done blindly, I was reading the plugs under two pulls which still showed black.

CEL light does not work either. Not sure why but it's another thing i'm working around.

Thanks for the suggestions though, still working on it and i'll update when/if I find out something.

[lazyboi444]

What Rb25 do you have S1 or S2? A Wideband would be of great help lol. Also for the Guy with the RB25 does it misfire at idle at all? (Suggestions for you both)Things to check for also is Cracked Ignition coil boot. Also check to see if they are arcing onto the valve covers. Check the voltage of MAF at idle and under a load. Set your Fuel Pressure to the correct settings that will also help in diagnosing the problem.

Check ignition module on both sides. Check wiring for Coils to make sure they aren't split or the sheathing has been ripped. Check each individual coil. Because at idle the car will run somewhat fine. But if you are missing a coil or it isn't firing properly at WOT its gonna matter a whole lot. I mean there are plenty of checks to go through. If i gave any wrong information somebody pluck my nose hairs.

Also as Joe said check the ECU see if its throwing codes. Because my ECU on my ka wont turn the cel light on the dash. But when i pulled it and put it in diagnostic mode it coughed up the cash lol. Had to choke it a bit

[fast_s13]

boost leak or timming... had the problem on two of the four rb20 swaps ive done

[Nissan2367]

Thanks for the input! I have a S1 RB25DET. It runs like crap at idle. It will run fo like 20-30 seconds then turn off. i was thinking the coils are arcing also so ill take a look at those again! I set my FPR at 42lbs without vacuum on it. I am running a AEM Wideband and at idle it reads about 14.5-15 but the second you hit the gas it goes right to the rich side and does not even read! That and it smells like straght fuel!Anymore ideas and trouble shooting things would be awesome! I dont know about the RB20 guy but all these make sense and are things i never checked! Last thing, i pulled my ecu to see if there are any codes but couldnt figure out how to make the light light up or even where it was so some help would be awesome!sorry if i thread jacked but i figure almost everything between a RB25 and RB20 would be the same!

[fast_s13]

Thanks for the input! I have a S1 RB25DET. It runs like crap at idle. It will run fo like 20-30 seconds then turn off. i was thinking the coils are arcing also so ill take a look at those again! I set my FPR at 42lbs without vacuum on it. I am running a AEM Wideband and at idle it reads about 14.5-15 but the second you hit the gas it goes right to the rich side and does not even read! That and it smells like straght fuel!Anymore ideas and trouble shooting things would be awesome! I dont know about the RB20 guy but all these make sense and are things i never checked!

what kinda fuel pump and fpr are you running? also stock bov?

[Nissan2367]

I am running a Walbro 255lph Pump and a Aeromotive FPR. Also i have a Top Secret BOV... It kinda sucks but i dont have the money for another HKS or Greddy right now. I am thinking maybe a boost leak too... does anyone know where i can get t-bolt clamps for cheap?

[nsxmatt]

Worm clamps should seal good enough at your boost levels. If you do decide to upgrade down the road, NAPA autoparts sell t-bolt clamps.

[MATTs14]

Im having similar problems but just at idle. It misfires at idle and till about 3 grand but then smooths out and pulls like a dream except for the boost cut in 3rd 4th and 5th. Ive switched to wasted spark so i know its not coils and im on stock boost. Im running a walbro 255, stock bov recirc, and im running a tad rich for the sake of not trusting a cheap stri gauge, and im using short intercooler piping and t-bolt clamps everywhere. Ive got the fuel adjusted to about 38 instead of the standard 36 because like i said im not sure if i should trust the gauge. I think its my alternator but im not sure. Ive also been throwing around the idea that its the fuel filter or plugs but new plugs dont phase it much. Any ideas guys? Maybe and hopefully this will help some of you guys out.

[Nissan2367]

Well just an update. I checked my CAS and and the tab on the end of the cam ane it appears everything is good. no the only thing i noticed is the little black dot in the middle of the cam sensor (RB25 S1) spins when the car is running. the shaft spins just fine but i dont know if this is normal so if someone could let me know that would be awesome.i also went out and bought "liquid electrical tape" my coils were missing paint where the bolts hold them in so i am thinking they could have been grounding out... figured i would try it.also i tried to get the ecu to flash codes but could not figure out how to do it so if someone could post a how to that would be awesome! Any more ideas would be awesome!Keith

[Shanejenkins1]

My car does the same thing also

[teamloco]

How do you test your coilpacks to make sure they are working correctly?

[Nissan2367]

How do you test your coilpacks to make sure they are working correctly?

zer...packs

[teamloco]

thx

[xX RB Xx]

My car does the same thing also

x2 but sometimes it doesnt do it and sometimes it does.. i have my ignitor sitting on the valve cover and im thinking its arcing.. we will see

[bkos90]

sorry for bumping an old thread but im having the same problem now and i was wondering if you ever solved the problem.

[bkos90]

So did any of you fix the problem? im having the same issue and cant find what it is.

[Conrad 2NR]

Did anyone check their TPS, especially after checking MAF, coilpacks and vacuum/boost leaks?