I have an obdII b18c1 swapped into a 96 civic. The motor was rebuilt (and poorly done) by a local shop. It took me a while to get it up and running but I finally got it on the road and after about a week I noticed two things.

1) It really really REALLY does not want to start when it is cold. If the engine is spring time temperatures (40-50 degrees F ambient temp) I have to turn it over a few times before it even fires and once it does I have to push the gas to the floor and let off repeatedly as rapidly as I can to keep it running. When it is at winter temperatures (around or below freezing) I have to crank on it for a solid few minutes before it will even start to fire and then I have to work twice as hard to keep it from stalling as I do in warmer weather. It will eventually stabilize and idle around 800 rpm, but as it gets up to operating temperature, the idle climbs to about 1500-1800 and stays there. I went through and cleaned out the entire intake manifold and replaced all gaskets while the block and head were in the shop. I checked that the IACV was in good working order (it was). Once the car is to where it will idle on its own, it sounds fine. No misfires, no backfires, it drives perfectly alright...
Ideas?

2) I got in it a little harder than I should have this morning running late for work (I'm still breaking it in) and before I knew it, the needle was at 6k and vtec hadn't kicked.
Before the rebuild vtec kicked and kicked hard at 4800 every time. Any idea as to what could have changed?

 

bump

 

Check the basics, compression test, leak down test, valve lash. Is the cam timing correct? How about your oil pressure?
Vtec solenoid screen clogged up?
Any fault codes?
Since you mentioned it was a very poor rebuild, you may have assembly issues/clearance issues that can only be addressed with another (correct) rebuild.

 

comp is good. Idr the numbers but it was one of the first things we checked. Valves are all good. did them myself. Cam timing is spot on. Don't know how to check oil pressure. Vtec solenoid is clean. It's a JDM ecu so I cant find a code reader that will work.

I don't doubt that the machining was done correctly with the rebuild, I just ran into a few bolts that they replaced without telling me about and they gave it back to me 180 degrees out of time. Bad service from a shop that builds top fuel motors and isn't used to anything Japanese. I went on a recommendation from a friend that tunes k-series motors and I got kinda screwed.
Like I said, once it gets running, it runs perfectly fine. The idle just seems to be really really low when it's cold (i.e. it stalls unless I pump the throttle at first) and high at op temperature.

 

180 outta time and they might have bent some valves.
Especially if they just threw the cams in and rotated it all outta sync. Really would be helpful if you cold log some sensor values, know anyone with tuning abilities that could swap in a chipped ecu with datalogging ?
Got a vacuum gauge? Might try and check vacuum to see how mechanically sound it is, cranking vacuum too.

 

I'm really the only Honda guy in my group of car friends, so swapping ECUs is out.
I do not have a vacuum gage. If I had fucked up valves, wouldn't it have trouble running too? and that still wouldn't explain my idle starting low and increasing as it warms up...

 

Do the wire jump trick with the plug on the passenger side and count the flashes .... Eks need two separate speeds one for the cluster and one for the Ecu.... Vtec also won't work till the car is warmed up to a point ... Check the ect sensor wiring and iat sensor since these effect the fuel tables greatly

 

Without seeing sensor values, its gonna be harder to diagnose. Does it seem to run really rich when its cold? If so, might Try and throw a new ect sensor in it, they're cheap.
Does it misfire at all when it's cold or just a low idle? It's possible the valves aren't sealing that well when cold, but seal up better as things start to warm up and expand.
Is the CEL on? I believe you can pull codes by jumping the SCS connector down by the ECU (same connector used to set base timing)

 

It runs really rich all the time. It's got the JDM type-r ecu in it (for some dumb reason).
It might be bent valves causing the problem with starting it. That would make sense. Still doesn't explain the idle increasing with temperature though.
The check engine light is always on. It's a b18 in an EK ...

 

Just to clarify, I am a mechanically-oriented person. I have a degree in mechanical engineering. Electrical stuff is all voodoo magic to me. All of these acronyms and wiring references are total jibberish, so I'm going to need you to spell it out a little more clearly for me to understand what you guys are saying.

I really do appreciate all the help you guys are offering, I just have a hard time wrapping my head around some of it.

 

There's a 2 pin connector (called SCS connector) down by the ECU, it's either green or brown i can't remember, if you jump it with a wire or paperclip or something, the CEL (check engine light) will flash a number of blinks. The long blinks =10 and short blinks =1. It will pause slightly between blinking the codes.
Ect =engine coolant temp sensor
IAT= intake air temp sensor
EK= commonly referred chassis code of 96-00 civics although technically EK is the civic type r code.
Pull fault codes first and get those squared away.