Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I am working on a 2000 Honda Accord 2.3L. The car only misfires at idle & as soon as you touch the gas the misfires go away. The short term fuel trim at idle varies from -10% to -25%. The fuel trims get much better as the engine RPM's increase, but as soon as it goes back to idle, the fuel trims are very negative. I am using the MS906BT & I get a random misfire code & eventually a P0301, P0302, & P0304. The parts cannon was thrown at this car from a local dealership and now it is my turn to take a look. The pre cat O2 sensor was showing it running rich since most of the time the O2 was above 450mv. There is now a new O2 sensor in the car & the cross counts & overall O2 readings are much better. I have ensured the EVAP system, fuel injectors are not bleeding down, fuel pressure regulator is good, cat is less than 1 PSI at 3K RPM's, & air filter is good.
I believe the timing is off. I hooked up my oscilloscope and had 2 channels hooked up. I had one channel on my pressure transducer & another channel on the signal going to the distributor from the ECM. My math calculations show the timing is too advanced by around 6.5 degrees. I took off the timing cover and lined up the timing marks & the timing does not seem to be off; but perhaps the belt is stretched since there is over 3/4" play in the belt & I can slide the timing belt off of the camshaft sprocket if I wanted to.
I have 01 V6
Going thru the same
Did you ever find out what was the root of the cause.
On mine I replaced
Fuel injectors
EGR plus cleaned ports
Map
TPS & calibrated
IACV
Spark plugs
Ignition coils
Fuel regulator and damper
Fuel pump
Good compression test
PCV valve
No vacumm leaks
