A month ago I swapped a b18c motor into my cx hatch. When the engine is warm, the motor absolutly RIPS and has no issues. On cold starts (car sitting for 2-3 hours) however, the motor seems to want to bog and stall. I have to hold it at 1500rpm to warm it up, because it wont do it on its own, like it should. After a minute or so of holding it at 1500rpm, i'll take my foot off the pedal, and it idles smoothly at 1000rpm. I hear that it could be a main relay problem, but I never had the problem before the swap, so what are the chances the relay would go at exactly the same time?.... unlikely I think...right? Do you guys think it may just be a slightly clogged injector acting up on cold starts? Any ideas from anyone would be greatly appreciated.

 

Seems more like a fuel problem, not a relay problem.

 

i used to have the same problem well still do but i went around it what year is your car? obd1 or obd2? if you have a obd1 check and clean your FITV located underneath your throttle body this thing controls cold temp idle

and while your at it also check and clean your IACV located behind your intake manifold

my car was obd2 converted to obd1 so i dont yet have a throttle body with the FITV so i had to get around this buy adjusting cold temp idle in the ECU via Hondata s300

 

I had this problem when I completely blocked off my FITV.. Sounds like your ECU is overfueling because it's expecting the artificial vacuum leak the FITV creates on cold starts..

 

I may actually be getting this problem also. Ive noticed im using more gas than normal.

 

ooo yep i also had to trim fuel at start up or it would bog up like it was gonna die

needa get a obd1 TB bah

erm its not really that its a cold start up bogging issue.

for your burning more gas than usual it could be..
cus..
its winter..
bad o2
bad fuel filter
your ripping it
thats all i can think about for now

 

I got same problem with my b18c. The rpms go up and down coming off the highway. And stays at around 1500 rpm when just sitting there. Got told it could be the manifold being clog or dirty but i'm putting an obd1 ecu into and getting it fuel mapped to fix it and make it run better then a tune and should be fine.

 

^ even when warm?