RB25det s1 problems

[bkt808]

rb25det s1
greddy intake
fmic
blitz dd vented to atmosphere
q45 throttle body
tomei fpr
walbro 255
arp headstuds
stock ecu
harness was bought used from a member on here and was using a s2 maf and connector so i switched it back to a s1 maf and connector

Problem is the car will start with the maf unplugged, but will not when maf plugged in. if i plug in the maf after car has started it will instantly smooth out idle and run good for about 5-10 seconds then starts to want to die and will aventually die, runs really rich and is fouling the plugs

I tried 2 different mafs, voltages on both mafs engine off ignition on were 0.3v-0.4v at the ecu, now while cranking im getting 1.3v-1.4v at the ecu which seems off according to the fsm.

checked continuity between ecu pin 26 and maf signal ground at the plug thats all good, checked continuity between maf signal pin 27 and maf plug and thats all good,

What i have noticed while checking continuity between pin 26 and grounds is that both ground wires at the maf plug (s1 has 4 wires- signal, ground for signal, ground for 12v and 12v power) have continuity at pin 26 on the ecu which leads me believe both grounds have been spliced together which i dont think is correct. would this be a cause for the increased voltage at the maf? would bad grounds cause an voltage spike or increase?

-have'nt shot ignition timing yet but still wont start either way i turn the CAS when maf is plugged in.

-has fuel pressure and injectors are firing

-has spark on all 6 cyl but maybe its weak?
ngk bkr7e gapped to 0.025

-pulled codes and getting code 55 all good

-new coolant temp sensor

any help is much appreciated thanks

[bkt808]

also does anyone know if i can ground that thick black maf wire straight to the chassis or engine block to try and eliminate it from it being possibly grounded with the air signal ground at pin 26

[bkt808]

could someone verify if my wiring is correct. this is how i set my maf up
http://vrqwna.bay.livefilestore.com/y1pFJ1eaapNu8_NfxcKI1AQHs-ZjioNAT78Hf_yKJTHZHQEtYerQ7fAyyxzYjSfZ_M8TZ5x3dGca ThKSMB_luPwL4yktHtn-NuM/NissanMAFS.jpg

[DJDANGER24]

Did it ever run smoothly with the Q45 throttle body?

[bkt808]

Did it ever run smoothly with the Q45 throttle body?

nope had this problem since first trying to start it, only time it runs smoothly is as soon as i plug the maf in and only lasts for a few seconds then wants to stall but revs up fine with no load in neutral, once i let off it fights to stay alive and will eventually stall, runs really rich
iacv? air reg?

[DJDANGER24]

If you tried two MAFS and the problem isn't fixed, then I am going to assume its not your MAFS. Have you checked your TPS? Not sure if you wired it correctly or set it properly on the Q45 TB.

I started to have an issue like this and just scrapped the stock MAFS and went with a new Z32 so it would rule out the MAFS completely.

[jdm213]

dude remove the q45 throttle body and put on the s1 throttle body and maf and tell me whats up

[bkt808]

If you tried two MAFS and the problem isn't fixed, then I am going to assume its not your MAFS. Have you checked your TPS? Not sure if you wired it correctly or set it properly on the Q45 TB.

I started to have an issue like this and just scrapped the stock MAFS and went with a new Z32 so it would rule out the MAFS completely.

i have checked the tps its getting 5v and i set it to .6v like fsm says,
even then ill press the accelerator to full open and try to start and get nothing it still wont start with maf plugged in, it tries to you can hear it kick over a little bit then starter just continues to turn it over and wont start

[bkt808]

dude remove the q45 throttle body and put on the s1 throttle body and maf and tell me whats up

hmm, whats with the q45 tb? has it been known to give problems? i still i dont think its a tb issue it can start without maf plugged in

[bkt808]

so recap is will start without the maf plugged in, and wont start with maf plugged in but i can hear a set of pistons fire for a second then the starter just keeps cranking it.
going to try to clean iacv, o2, and ground ignitor to firewall today.
any other ideas?

[DJDANGER24]

Replace the MAFS

[bkt808]

i just double checked the tps with ignition on, 0v? huh? tryed to adjust it and while trying to adjust it i just dont get anything between 0v and 2.5v it just jumps straight to 2.5ishv? bad tps?

[bkt808]

things i did was clean iacv, clean o2, and wire the mafs 12v ground (not signal ground) to firewall.
also i guess i had the tps connector plugged into the wrong plug on the tps :facepalm: so plugged that in adjusted it to .4v closed and tryed to start it wouldnt start with maf plugged in OR unplugged i could hear it wanting to turn over but didnt.

so my lovely fiancee which who was inside the car trying to start it for me while i was messing with the idle screw on the iacv was like "maybe you need gas". i didnt think that maybe the gas was bad cause it was only down for a couple of months. so i figured get a gallon of 92 throw it in there and go from there.

so we did that and the car started without the tps and mafs plugged in. i had to play with the throttle plate to get it to start and idled kinda rough, i plug the tps in instantly smoothed the idle, then plugged the mafs in and it ran good at times, i could hear it surging and wanting to die and then the surging goes away and runs excellent then surging comes back again and so on. i think it might be because of the bov vented to atmosphere and maybe the stale fuel and good fuel mixed together? im going to also throw more fresh fuel in there to knock out the possibility of fuel still being crappy cause its only mixed with one gallon of fresh fuel as for the bov im not to sure what i am going to do as my bov is where my battery was. id hate to run a hose all the way across the engine bay to the intake.

so anyway in the first place the car wouldnt start with the maf plugged in so the car warmed up fans came on so i turned off the car and went to start it again and had to play with the throttle to get it started, idled rough and would die if i didnt play with the throttle, but if you keep it from dieing it will eventually idle pretty stable as surging comes on and off.
so for now im waiting till it cools down and im hoping for no problem with starting it cold.
questions:
has anyone had and similar experience with bad fuel and not starting or hard start?
has anyone had same situation and turned out to be iacv or air regulator bad?

[bkt808]

forgot to include when i rev it up and let off theres a thick black cloud out the exhaust(rich) when bov is open.?
sometimes i can hear what sounds like knock(detonation) at idle then it goes away then comes back and so on.?
also when i unplug my maf while the car is running it will die? is this normal?

[bkt808]

put another gallon fresh 92 fuel, still having to tap the throttle to start it but it cold starts and thats the main thing. Idles excellent after about 15 seconds or so of tapping the throttle to keep it from dying. IACV?
once warmed up if i rev it up and let it drop back to idle itll start to do a quick surge at idle and almost stall at times, it will eventually come back to a good idle if i keep it from dying by tapping the throttle.
Do you guys think thats because of my vented bov?