Hello everyone, I picked up a F23 2001 Honda i4 2.3L Vtec accord with 140k for my mother about 8 months ago and i've been chasing an issue where the car is stubling and misfiring badly Under Load. When the car is not under load and sits in the yard you can Rev healthy to your hearts desire.
When driving on the other hand, it will be good for a minute or until you really mash on it, whichever comes first. Then it will start missfiring whenever you go above 3k rpm, consistantly missfiring and stumbling, dying completely sometimes too.
I've replaced : vTec Solenoid, cut cats completely off to free up exhaust, new fuel pump, cleaned fuel injectors, flushed gas tank, cleaned fuel rail, Cleaned EGR carbon buildup, replaced any old vacuum hoses, new MAP sensor, removed air intake box, new knock sensor,
new spark plug wires, new distributer, new spark plugs (correctly gapped), new idle air control valve, checked compression on all cylinders which ranges from 155-165.

What I havnt tried: Timing, Crank Sensor (i have a new one), Valves out of spec, there is a nut that holds the throttle body to intake that is off/lost (3/4) secure it still and it seems solidly mounted

It was a gift to her after her drivers license got reinstated for no more seizures, and now it's turning into a pain in the butt.

Any insight? thank you, I had a professional scanner which gave me MAP (before I replaced it.. to no avail) and two or three dealer M-Codes. (i'm trying to locate the file now)

 

Post the codes on here and it might give you a sense of direction. Right now you are throwing parts at the car, and you'll need to diagnose and not replace any more parts. Replacing random parts can get expensive when you replace a working part. The more siginifcant risk is that I've seen new parts out of the box fail, so you essentially created a new problem plus the original problem and diagnosing becomes much harder. Please keep the old parts you replace in case you need to reinstall.

Since you have a professional scanner, look at some live data at idle then while driving. You may need an assistant when driving the car if your scanner can plot data.

I'd start with the short term fuel trim bank 1 and long term fuel trim bank 1. Open/Closed loop. Maybe the 2 O2 sensors as well. When the engine is warmed up and at idle, let us know the approximate fuel trims as they do fluctuate. Raise the idle in park to about 2000 rpm and report the fuel trims. Take the car for a test drive and report the rpm when you have problems and the short and long term fuel trims. The bank 1 O2 sensor while in closed loop should oscillate up and down. The bank 2 O2 sensor should remain somewhat constant.

Let us know what you find.