Did the swap the other week but didn't throw the wideband in till yesterday. Cruising afr is mid 14s, that's the o2 sensor doin its thing. Wide open is a tad lean right about 14:1through low and mid rpm. Hot idle is money, just about 15:1. Cold idle is lean as ****, about 18:1. it studders and stumbles around in the rpm range a bit but doesn't stall. What's the likely culprit here, bad cold start maps in the ecu? Coolant temp sensor bad? I gotta get it fixed or I don't think it will want to run in the cold mornings when winter sets in

 

blah, wound wound up putting neptune in, pretty much got it set straight but ive gotta say this setup is giving me more **** about good idle afr than my turbo car with 880cc injectors

 

bump it back. put the oem ecu back in so i can get it inspected this week. its bad, afr on cold start and up until about 140f is between 17-18:1, and i even saw it spike lean 19:1. its not just idling if i give a bit of gas up to 2000 rpm its lean the whole way up. once warmed up it runs like stock.


is this like an fitv issue or what? im worried it might not stay running when i go to work and its 20 degrees outside

 

you got a p75(ls) ecu running a b20, not enough fuel

 

can this be offset by increasing fuel pressure?

i lowered my fuel pressure to lean out the idle on my gsr after exhaust upgrade.
i turn the pressure up it gets rich all the way through. turn it down and it leans out to 14.2 or so

 

see i thought about it, but once the car is warm the afr is pretty much spot on. im worried that if i put an adjustable fpr on and richen up the cold start, the thing will be too rich across the whole load/rpm.


when i put the neptune on a few months ago it wanted to idle lean right off the basemap i had to add a bunch more fuel in. im wondering if there is a sensor that is sending erroneous voltage to the ecu till it warms up..something is not right with the correction factors.

today i swapped out the ect to the ecu sensor with a known good one, fixed a pinhole leak in the coolant line to the heater core and swapped out the iacv with another one. no help. the primary o2 was replaced last year with a new oem one so its not too old. it was also in the ls swap i previously had in the car and it was not running lean when cold. in fact, the ecu, intake manifold, tb, injectors and fpr all came from that ls than ran fine for 30+miles (till the crank bolt backed out..cheap craftsman china torque wrenches)

 

well your ecu runs in open loop mode untill O2 sensor warms up
then it starts adjusting fuel according to O2 sensor reading to get it close to target AFR.

can you borrow one from anyone to try?


what car is it in anyway?
why not use b20 ecu from a manual crv if its obd2

 

what i meant is when cold it runs off your maps on ecu (which is LS motor)
when warm it tries to keep AFRs as close to target afr as possible

 

Yea you are right, the o2 sensor keeps it close (14.2 to 14.8:1) but when operating just off the map its lean. Im gonna bum the adjustable fpr off my other car after work today and hook it up.

 

swapped over my aem from my other civic. i got the cold idle to get into the 15s which is not dangerous and im ok with it. i had to turn it up into the mid 50 psi range.
interestingly enough, at wot it still runs leaner than i would like, with an afr between 13.6-14.0:1.

 

fuel pump doesnt hold constant pressure.
at full throttle i belive it will still give you same pressure as stock
it drops like 10 psi or something beause of more flow.

 

True, but on the neptune it holds steady high 12s afr to redline same fuel pump. I also checked and there isnt a big voltage drop toward redline i carry over 14.1 volts the whole way through. Oh well I don't really care im not going wot unless logging or monitoring, and I fixed the lean cold start which was the primary concern. Thanks for the help peeps