How does the 0411 detect misfires?

[BOTTLEDZ28]

I have a 98 Tahoe with the 0411 ECM swapped in. I have also been running the Dash Command app to monitor various sensors and what not in the engine. I was getting a boat load of misfires on various cylinders at random times so I decided to replace the plugs, wires, cap and rotor to hopefully fix the issue. All Delphi parts were used along with Delco plugs. Well, the random misfires are still there.

If the ECU is detecting them then that should rule out the possibility that the misfire is from carbon build up on the valves right? I mean how the heck would the engine know if there was carbon build up. It just fires the plug when its supposed to.

So, this leads me to think that I have something else wrong. Possibly a faulty ECU or tune or maybe a pickup coil in the distributor. Can anyone shed some light here on this?


I am NOT getting any check engine light other than the low voltage detected at the EGR. Lextech tuned the ECU and he cannot figure out why I am getting that code. The engine runs the same cold or hot with the EGR plug plugged in or unplugged so its pretty much a hiccup in the tune which is causing the light to be triggered. It comes on as soon as the engine fires up. I can shut it off while driving and it will not turn back on until the engine is restarted. Not sure if its related to this misfire problem but I figured I would put it out there if its revalent

 

[GMRedline]

Have you felt any loss of power? The reason I ask because it is common for scan tools to detect and show missfires but they arent necessarily real or a problem. If you get an engine code, then it's a problem.

 

[Mangonesailor]

When I put my 0411 in, I got a LOAD of missfire at idle, and only idle. It was on most of the cylinders, and the way I figured it out was relating the total missfires on each cylinder to their relative position in the firing order. I had to shift it a few cylinders for it to make sense, but it turned out that my dizzy gear was knife-edged on one half of it. I replaced the whole assembly with a summit unit and those went away (but I got a dizzy position offset CEL).

The way it figures it out is the ECU knows the rpm that the engine is running, so it knows how often the crank position sensor will go high or low (see or not see) ass the pickup wheel passes it. It has 4 "lobes" on it.

So, with the rpm known, it knows the time it should see the wheel, how long it should see it, and when it should be out of the way. When the engine misses, the speed of the crank changes, therefore the time when the crank sensor sees the pickup wheel changes. When this happens the ecu will compare that to which cylinder just fired, and logs it as a missfire.

Here is a thread about my own 0300 issue. I also tried blocking off the EGE, no dice.

 

[K30burb]

go in and program out p01336

 

[BOTTLEDZ28]

Lextech is going to be tweaking the tune so that the misfires that are present do not trigger the TC to unlock. At least this will hopefully save my transmission throughout the winter while I figure out what crate engine I want to buy come spring. The engine is sick. Most likely a failing head gaskets since I am loosing coolant it the exhaust has that nice sweet smell. Intake gaskets were done a few months ago so Im 99% sure I eliminated that as a cause for coolant loss.