sr20 running super lean please help.

[Dbruesch]

usually do the reading not the writing here. not looking for a handout just someone elses insight on the issue.

redtop sr20 stock internals
fmic
c/a intake
aem afr gauge
greddy boost (BAR)


I read up on the issue because i know it has been beaten to death, but i cant for the life of me figure out specifically what is wrong with my engine and would greatly appreciate any help or advise.

i had this engine in my previouse s13 with the same setup and the afr were always perfect. i crashed the car and it sat for a year. i bought another s13 recently installed the engine and was running it for about a week (ran perfectly just as it did before) until i installed my afr gauge. on startup it will sit at 1200rpm and the engine will stay pegged at 14.8 for less than 10 seconds then it will progressively climb to around 17.0 as the rpms drop to around 900rpm. the thing that really gets me is that every now and then the rpms will raise and the afr gauge starts reading just as it used to 14.0 at idle, 11.0 WOT, and like 12 something at cruising speed. but as soon as i notice the idle drop (involuntarily) the afrs climb straight back up to around 17.0

steps taken...
code 55
verified vacuum system with pressure tester
replaced both upper and lower i/m gaskets
iacv gasket replaced
iacv cleaned thoroughly
t/b gasket replaced
exh manifold gasket replaced
turbo outlet gasket replaced
other various exhaust gaskets were replaced to ensure afr sensor is reading correctly
i didnt check the V coming from the sensor but i placed it in a rag with gasoline and watched afrs go down to 10 and when released from the rag they climbed to 18
hardwired fuel pump and am now seeing 14.0V at the pump and around 39 to 40 psi right next to stock fpr.
tripple checked and sanded all grounds.

ive done this within the past 2 days and it is consuming my life...
please help.

[Kingtal0n]

narrowband installed? you should be in closed loop, letting the ecu adjust a/f while driving. if the a/f is walking into the red (17's) then it could be your ecu trying to use closed loop, seeing 1Volt on the signal wire for o2 narrowband, which would cause it's block learn multiplier to pull fuel

[Dbruesch]

probably should have mentioned when i unplug n/b o2 sensor on exh mani afr's dont change at all, will check voltages on monday

[Kingtal0n]

probably just change it skip the diagnosis, they are cheap. get a 1-wire at pep boys if you need to for like $12 it will work

[Dbruesch]

alrit so i replaced o2 sensor wit no success. in fact sometin really crazy appened as soon as i start te car i ear a tickin noise from enine so i pulled te valve cover to inspect and everyting looks good so i wrap it up and put it ack toeter and now my car wont even stay on for more tan 2 seconds wit a really messed up idle. trowin a code tree 4. any ideas. sorry for talking like a jamaican man spilled soda pop on my keyoard...

[inopsey]

check the voltage at your injectors while running. move around the wiring harness with the car running see if that causes a change. i would also replace the iacv

[steve shadows]

Yeah check the pins on your ECU for injector driver output...This happened on a few cars a while a back due to corrosion on the pins. Also I recommend the smoke testers (smoke machine style vacuum testers) if you can find a shop with one locally who will let you borrow one or do a test for you it's worth it...we've even caught boost gauges leaking before. Thanks!

[Kingtal0n]

redtop sr20 stock internals
the thing that really gets me is that every now and then the rpms will raise and the afr gauge starts reading just as it used to 14.0 at idle, 11.0 WOT, and like 12 something at cruising speed. but as soon as i notice the idle drop (involuntarily) the afrs climb straight back up to around 17.0


This indicates you have an electronics problem, or a problem with the communication of electronics. At this point you still want to do the easy steps before taking anything apart:

1. Check for boost leaks by pressurizing the plumbing, including the cai
2. tune up, change plugs, clean the air filter, do a compression check for good measure, change coil packs if you can
3. replace the maf/ecu/injectors/wiring as necessary with good known units
4. Once you've rules out the leaks, swapped electronics, you are left with only engine internals. At that point, we will begin from there.

[Dbruesch]

just had a chance to look at the car today and fix keyboard,

update when removing valve cover old idle air hose running to bmc retired and developed a long crack causing extremely rough idle and threw code 34. replaced hose and car regained good idle/crappy afrs. today replaced plugs (bkr6eix) and readjusted tps. since this car has developed a slight hesitation inbetween 2000 and 3000 rpm, and feels super funky on decel, going to readjust asap and see if anything changes. making a leak tester right now and will update asap.

i dont understand why the computer wouldnt recognize the o2 sensor plugged in or unplugged. it just randomly goes into open loop and runs a hell of alot better whenever it wants to (shortly after startup, never when fully warm). i will post a video later thanks again guys

[Kingtal0n]

i dont understand why the computer wouldnt recognize the o2 sensor plugged in or unplugged. it just randomly goes into open loop and runs a hell of alot better whenever it wants to (shortly after startup, never when fully warm). i will post a video later thanks again guys

find the single wire that the oxygen sensor communicates to the ECU with and either put a gauge on it or a volt meter. it should be flipping from 0.005v - .995volts while in closed loop. if the ecu is having trouble communicating with the o2 sensor you get the problem you describe

[Dbruesch]

tested for boost leaks today and found that the O ring that sits inbetween tps and tb is leaking badly, also found a few others such as couplers and a tiny one coming from the housing of the iacv. so the iacv needs to be replaced but can i purchase the o ring alone for the tps? seems a little ridiculous to replace the whole thing...

-king talon, going to make sure computer recognizes o2 signal and update later.
-inopsey, no change with wiggling wires (wiggled the crap out of them)
-s shadow, checked injector drive output everything is fine. you were right i had a whole bunch of corrosion on those exacct pins. almost poopedadook

[Kingtal0n]

you could always buy one of those cheap used narrowband a/f gauges to sit in the car with you while you drive. it flips from green to red all day to let you know the a/f ratio is being mediated by the ecu/o2 sensor.

[Dbruesch]

If i have a poor connection to my 12v (red wire)coming off of the o2 (im seeing about 4v) would it give the same problems i am describing? should it just be in open loop longer until the o2 heats up, or is it affecting the overall signal to ecu?
Ordered new iacv and tb coming in on monday. As soon as i can start the car ill fix/check voltages and update.

[Dbruesch]

Problem solved.

the person who did my harness repinned the brown plug next to th e battery. Moved pairc wire and switched it with the 12v ign start wire. he had run both the o2 sensor and iacv 12v wires to this source.
Also had a poor connection to ecu 12v. IM at 14.6 at idle, 12.1 wot, and like 14 cruising. I still haven't gotten my new iacv or TB as they are both leaking air.
Thanks for the help guys. I really appreciate it.