Hello, I have a B20v with hondata that will start to run rough after it warms up. I came to a light one day and the engine died. Had to rev the engine to about 1500 for it to stay running. Also in the back yard for example when idling and it gets up to 180-190 degrees the engine shakes the af ratio runs lean and my volt gauge reads about 10v. there are no cels. I have replaced the alternator distributor iat sensor. I know this isn't a guarantee. It also happens after I run the car hard. After an autocross run or an oval time attack run. I have an event at VIR at the end of October and need some help please. Or maybe steer me in the right direction. Thank you, Brian,

 

Check your TPS in the data. See if it is reading above zero when idling. Reset if needed. Be aware if it's floating around with engine vibration, heat, or whatever - you may have a tired wire or imperfect connection somewhere. record a log from cold start all the way up to operating temp and see if TPS is returning to 0% every time you get off the pedal.

If the TPS is not going to 0% when you are completely off the throttle, the ecu doesn't know to switch over to idle control and the engine sputters and often dies while trying to breathe through a closed throttle without help from the IACV.

Quite possibly your issue is something else, but this reads like non-zero TPS problem.

 

I just ran the engine and it produced the same problem. TPS was at 0%. Engine warms up and fan cycles once then the afr goes into the 20s voltage drops below 11v and idle is below 800 rpm. Car was sitting still.

 

Low battery voltage reduces the fuel pump speed... thus, leaning out the engine. How high do you have to run the engine to get the voltage back up to 13.8 - 14.4 volts ?

 

^this.

The low idle and stumbling can also drop the idle too low for the alternator to keep up. It can be kind of a death spiral.