stalling under braking...vac leak?

[nissanman04]

whenever i brake i have to rev the engine just to keep it running. sometimes it won't even respond to the throttle, like the fuel is cutting out. if i happen to be braking while still in gear, i get a really big backfire. i'm assuming that i have a vac leak somewhere, possibly more than one. also, i'm using a KA coolant temperature sensor because the one on the rb20 was broken. just wondering if the sensor could be causing the engine to miss. i'm planning on resetting my timing this weekend to rule that out as a possible cause as well. another possibility could be the tps i guess.

btw...the engine is pretty much stock, running a walbro 255 and a nismo fpr at around 50psi

just wondering how others have taken care of similar symptoms...thanks

[eh?]

You might wanna get the correct temp sensor and bring your fuel pressure back to spec...

[Eikon]

Fuel pressure should be 43ish... not 50. RB coolant temp sensors are hard to get. Talk to ozzie!... he can source stuff for you. Or talk to Takara... they might have some laying around.. Hell, I might even have one in my garage.... I'll look around..

Anyhow... I have the same issue and I can tell you that my fuel pressure and temp sensor are fine.

Do you have a blow-off valve? Is it venting to the atmosphere or does it recirculate back into the plenum?When you let off the gas it blows off the excess pressure, then actually leaves you short on intake air momentarily. I beleive this is what's happening to my car and yours.

I'm assuming this is the proper explanation... Can anyone else (Carl/Kamin) verify this to be correct?

On the plus side.. it's a great way to learn to heal-toe technique as you have to give it some gas as you are braking in order to keep from stalling.

[Valley]

yes, thats how it works. metered air is being released from the system which causes an extremely rich condition momentarily (a huge leak). another symptom of this is bogging when shifting

[nissanman04]

yeah i reset my fuel pressure to 43 w/o vacuum, didn't help at all. those temp sensors don't cross-reference to any US car?

i have the stock bov and it is recirculated. haha i can't practice heel-toe because it won't rev while i'm on the brake pedal.

it stalled out completely like 4 times on my way home from work tonight. it took like 5 tries each time to get it to start again. well, it would start every time but it wouldn't respond to the throttle at all. it has gotten to the point where it is not driveable anymore. at least i have all day tomorrow to try and troubleshoot...

[Carl H]

pull codes.sounds like the tps might not be set.use what ever sensor you have to ka/z32 depends on what 'series' rb20 you have doesnt matter really tho they all read the same.

[DrifterTom]

sounds lika a tps problem to me too, i think the code will be 43, but i am not sure

[nissanman04]

ok now i'm getting code 12 from the ecu (MAF), which is really weird since i didn't change anything and 5 minutes before i got 55. also my fuel pump has stopped turning on, i have narrowed this down to a faulty fuel pump relay. anyone know what could cause a relay to go bad all of a sudden?