Hi:
I notice the engine almost dies when the check-engine light goes off. This bring, when I let the light go out by itself, after something happened. Once the wire came off a temp sensor. Whatever the cause, this time a misfire, when it eventually clears, it almost stalls the motor.
BTW, does anyone know how a misfire is detected? Is it a pulse in the exhaust gas, maybe oxygen?
Thanks Folks
Harry

 

Well, my first suggestion would be to check what code(s) you actually have...................

 

To answer your question:

Generally misfire is detected by looking at crankshaft rotation funkynesse. That would be done through the crank position sensor. Makes you wonder if a Chinese Replacement Auto Parts sensor or flex plate affects misfire detection.

 

Hi and Thanks! OK. That sounds like a wobble in RPM is sensed. There is a bit of a shake at times. I've changed the MAP sensor and the Idle Control valve. Neither made a difference. The TPS voltage looks smooth and sitting around .83V at idle. I changed the plugs which all looked OK anyway. It feels to me like it's running lean or rich sometimes. I'm hoping not an exhaust manifold leak. This looks to have 4 EGO sensors and 2 Cats all welded together.
TY
HarryHydro

 

Do you have a single cylinder misfire, a random misfire? Post the exact code(s) here for comment. With OBD codes, the devil is definitely in the details.

 

Hi: I can’t remember the number. May be 204? But definately says Cylinder #2 misfire all the time, everytime it happens. I had the coil pack off, changed the plugs that looked surprisingly good, didn’t make a difference but I didn’t poke in the boots for springs.
It runs roughest when it’s hot but been off for a half hour or so. Almost like heat-soak.
The weather is cool.
Harry