runs fine till full throttle and full boost

[tintdude69]

ok well i got a 89 240 with a rb20 new iridium plugs and 255 fuel pump and everything is perfect except one little thing..it starts right, free revs fine, drives fine, but when i hold it to the floor and as soon as it hits full bost it pops and cuts out. so i traced the maf wires and checked for resistance and they are all fine. but when i go by the manual and i use a multimeter i prob3 the neg from the meter to pin4 ground and positive to pin2 signal like it says to do it stalls out. its not a loose wire in the connector though because if i probe it with a paper clip its fine but soon as i touch the multimeter to it it stalls...im not getting the 1v with the key on im getting like .20v and getting like .3 when i blow on it not the 2v its suppose to be..i cleaned the maf out with electronic contact cleaner but its no better....any clues?

[Joe]

how much boost are you running?

[tintdude69]

still stock..it does it around 9psi

[Joe]

check the resistance in your maf wires

touch one probe from the multimeter to the plug at the maf, the other to the pin on the connector where it meets the ECU

[tintdude69]

did that like the manual says....signal on the maf plug to signal on the ecu and the ecu ground from the maf plug to the ground on the ecu...no resistance on either so no short

[Blown240sx]

is the car getting fat when you start cutting or leaning out? If its getting fat(rich) then you could have a boost leak that occurs when full boost occurs.

[tintdude69]

its not jumping to full rich but its still rich when it happens...ill put my friends tester on it and check for leaks....but i still dont get why it stalls when checking the signal wire

[tintdude69]

did a boost leak test and nothings leaking at all....anyone?

[blues14]

when you say 'cuts out', are you saying the power is just goneor flat? or do you mean the motor shuts down as in turns off?

If the power is cutting out.....Try this......run it till it cuts out, (like in 2nd gear) and immediatly shift into 3rd and give it 1/2 throttle......let us know what happens....... while doing this, look to see what RPM this is happening at. also try this at 3/4 throttle instead of full throttle and see if you get the same result.

you can also try advancing you timing a bit (by cas....mark your origanl position) to see if that helps.

if the motor is shutting down......I dont have a clue.

[tintdude69]

its stuttering adn back firing..ive tried that getting on the highway and its fine if i run it till it does it then shift and half or 3/4 throttle it

[monkeyofdrift]

Does the car start to stall/acts up, when you are at low rpm's? and when you go to shift to neutral?

[tintdude69]

no everything else is completely fine.

[digzsublime]

Mine cuts out at the top of 3rd gear just like you are describing. When I check my SAFC it shows the MAF is maxed out. What MAF are you running? Stock?

I'm not saying you're maxing out you MAF (No flames please). But it does sound like it could be related to the MAF in some way. Nissan MAF's are know to do weird stuff.Otherwise if you're sure there aren't any boost leaks I dunno.

[BigPar]

you'd think someone would have figured this out by now. Mine is doing the same as described on my RB25, and I've tried numerous things so far to fix it. I installed a nismo fpr, didn't help. I redid my timing and have it exactly on 15 degress (4 marks from the left) and still cut in and out. I'm not runnign exhaust, so I don't know if it's just not enough back pressure or what. The rpms dive bomb and try to stall at sudden stops an dlow rpms. It stalls between shifts whith the clutch held in. I'm tempted to hook up a z32 maf and safc to see if my stock maf is screwed up. Every test has been a big let down so far. The timing helped to curve it somewhat, but it's still there. and No boost leaks.
Modified by BigPar at 9:10 PM 10/17/2006

[tintdude69]

im still running stock maf.. there isnt anything around here nissan wise but i know one person with a maxima so im gonna try his maf if i can ever get ahold of him before i waste money on one

[monkeyofdrift]

you'd think someone would have figured this out by now. Mine is doing the same as described on my RB25, and I've tried numerous things so far to fix it. I installed a nismo fpr, didn't help. I redid my timing and have it exactly on 15 degress (4 marks from the left) and still cut in and out. I'm not runnign exhaust, so I don't know if it's just not enough back pressure or what. The rpms dive bomb and try to stall at sudden stops an dlow rpms. It stalls between shifts whith the clutch held in. I'm tempted to hook up a z32 maf and safc to see if my stock maf is screwed up. Every test has been a big let down so far. The timing helped to curve it somewhat, but it's still there. and No boost leaks.

Modified by BigPar at 9:10 PM 10/17/2006

Yeah, I'm having the same problem, the only thing I can narrow it down by is the MAF, HKS does sell a unit called eids, helps with the stalls, but nevered tried it, I guess when I get my turbo upgraded the Power FC w/z32 MAF will fix it. *crossing fingers*

[blues14]

when upgrading to z32 maf, do you need supporting mods? or is it just a straight swap?

[BigPar]

with the z32 maf you need an safc or something of the sorts to control it.

[wawazat8402]

you'd think someone would have figured this out by now. Mine is doing the same as described on my RB25, and I've tried numerous things so far to fix it. I installed a nismo fpr, didn't help. I redid my timing and have it exactly on 15 degress (4 marks from the left) and still cut in and out. I'm not runnign exhaust, so I don't know if it's just not enough back pressure or what. The rpms dive bomb and try to stall at sudden stops an dlow rpms. It stalls between shifts whith the clutch held in. I'm tempted to hook up a z32 maf and safc to see if my stock maf is screwed up. Every test has been a big let down so far. The timing helped to curve it somewhat, but it's still there. and No boost leaks.

Modified by BigPar at 9:10 PM 10/17/2006

Where is your exhaust dumped at? You may not have enough piping after the O2 sensor to keep it from getting a false lean reading due to the fresh air contacting the sensor.

[tintdude69]

it was dumped right infront of the rear tire but now i got a muffler on it so its all the way to the back. i tried unplugging the tps just for the hell of it and it was a little better and felt faster but still stuttered. i know thats not gonna help but im getting desperate till i find a maf to try too

[tintdude69]

ok so im getting a code 12 an 21...maf circuit and ignition circuit....i know the maf,tps, and cas are all tied together so im sure a bad maf would cause a misfire and through at code 21..

[ichriscaines]

Any updates I'm having the same prob.

[driftersilvia240sx]

Honestly check you tps .5 closed w.o.t. 4.5 ohms maybe

[Tenchuu]

On the MAF, is known working? i had to cut off the top of the square and re-soler my contact points to get my MAF to read better. research i did years ago showed this was an issue with these RB25 MAF having brittle solder on the PCB.


Not saying this is your issue, but for other people having a problem, i found out that i had water pooled around my spark plugs and had this exact issue. It sputtered and backfired under full throttle. no clue how it got under the hood and on top of the engine, guessing it was something about sitting on the driveway slant.