I'm getting a lean missfire at idle and cruise but it seems fine at wot or maybe it's just not as noticeable. At start up it'll idle up then when it comes down it'll go full lean. When I'm cruising it'll buck sometimes even when I run it rich. However it is alot worse at 14+ afr. Then sometimes it'll go lean while driving for no reason. This has been tuned it is definitely not the tune. I've checked and replaced litterally everything. It ran great after build and tune.
build
H22a4
11.1
Pro1 cams and vt degreed
Ported head/ intake 70mm tb
525cc fic
Hondata s300v3
I've replaced all sensors and checked all wiring
Plugs, wires, coil, distributor
Fuel injectors and pigtails
Fpr, fuel rail, fuel pump, fuel filter
​​​​​main relay, ecu, s300
Compression 235 all cylinders
Fuel pressure steady 48
Leak down below 5%
Vacuum 18.5
Could I be getting air in the fuel line some how?
I'm getting good voltage to injectors. I've even replaced injector wiring and all grounds.

 

valve adjustments ok?

 

Has the car sat at all, enough to maybe have the fuel in the tank go bad, or an injector to clog or stick? What shape are the plugs in? If you are sure that you have good consistent fuel pressure you should be able to rule out the fuel pump and filter..

 

Thanks for the reply. Yes valves have been adjusted

 

I was driving it daily when it started. I've since ran the tank empty and replaced entire fuel system except the fuel lines. Ive tested and replaced everything. It's either got to be fuel lines or hondata s300v3. Hamotorsports was awesome and sent me another ecu but no luck. I also paid hondata $50 to look at s300 but they said it was good. However the red light comes on sometimes for no reason. Onboard datalogging is turned off. I used a friend's s300 and it ran alot better but i could fill it barely buck sometimes. But that may have been from worn plugs. They only had 1,000 miles on them but was ran rich and lean due to issue. Im going to try crome and see if the issue goes away.

 

Hmm, and from how you talked about it, do you have a wideband on it, and you are seeing accurate air fuel ratios?

I am sort of leaning towards vacuum leak now. Do you have an IAC valve, or is idle controlled solely via throttle body and ecu? There are plenty of places that leaks can develop, so its probably worth checking all around all sealing surfaces from TB all the way to the head.

 

Thanks for reply but I already have many times. The vacuum is steady. I've used propane, cleaner and plugged all vacuum lines. I also changed IM and throttle body. I'm pretty good with cars but this has me beat. I've also disconnected iac and plugged it for test