rb25det s1 problems

[bronson808]

rb25det s1
greddy intake
fmic
q45 throttle body
tomei fpr
walbro 255
arp headstuds
stock ecu
harness was bought used 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 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

[bronson808]

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

[Carl H]

the grounds shouldnt be spliced together, there is a dedicated ground for the maf signal and a chassis ground...fix that and see if it rectifies the problem.

[bronson808]

the grounds shouldnt be spliced together, there is a dedicated ground for the maf signal and a chassis ground...fix that and see if it rectifies the problem.

ok will do, i just check my tps and it is getting power 5v and as for the signal it was giving 0v? i tryed to adjust it and i dont get anything inbetween 0v and 2.5ish volts, it just jumps straight to 2.5v? bad tps?

[Carl H]

bad tps for sure...might have wired in the wrong plug.
q45 bolts right on and the sensor plugs right in with no mods on a s1 harness.

[bronson808]

the tps connector was untouched on the harness i believe, i just bolted the s1 tps to the q45 tb, the q45 tps that came on my tb was a square style of plug wont plug right in, but i believe i could just swap connectors? am i correct? pins all correspond to the same spots on both?

edit: nevermind im looking at the wrong plug, q45 tps does bolt on and just plug and play, ill update as soon as i get to try and start this thing with the q45 tps

[bronson808]

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( carlh you were right) 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". 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 it 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 with the car warmed up fans came on 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 bad?
what does the air reg do?

[bronson808]

forgot to include when i rev it up and let off theres a thick black cloud out the exhaust(rich) when bov is open. i know that i have to recirculate
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 the car will die? is this normal?

[bronson808]

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?