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!
Has a stumble/misfire only at hot idle. More noticeable in gear.
Fuel trims are about 128/134 so good. 02 sensor cycling rich and lean.
Spark is solid from coil on scope and cylinder drop test. Each cylinder drops more or less equal rpm at idle.
Truck runs perfect at all other throttle openings and conditions.
Has a new distributor, plugs, and wires.
I've checked timing it's spot on with the ESC disconnected. Doesn't waiver with that disconnected. Misfire is still present with base timing or computer control.
On the scan tool the timing moves around from about 16 to 20 degrees.
I believe this is a random misfire. It's not constant either.
If you shut the truck off hot and let it sit for a couple minutes. Restart and it runs smoothly for a couple then it starts to stumble.
Adding a fuel source about makes the engine stall.
Vacuum is steady. Very minor wavier in the gauge. Less than 1" of Hg of movement. Passes tail pipe paper test.
No codes, data from sensors looks normal.
It has 255k on it. I personally wonder about timing chain stretch.....
If it misfires when hot ohm test injectors when cold and when hot odds are one of them is having an issue otherwise the ignition coil is shorting out when hot or the ignition control module in distributor or if it's mounted externally is starting to fail scope those when cold idle then save and compare to a hot idle.
