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Hi 7.3 experts. I understand the cali emissions trucks which all Excursions are run the "cylinder contribution test" essentially all the time for "misfire detection" which can often give up false codes for poor performance on cylinder 2 and 8. I am not really worried about getting this code because the engine is running super smooth, getting great MPG and making oodles of power when I give it the boot. But I have put something like 70k miles on this truck the last 6 years and MIGHT have seen this code one time in the first 6.5 years. The last few months I have gotten this code twice with no obvious reason in the same situation. Sitting in the truck idling in my driveway finishing my podcast I was listening to driving home from work. As long as the engine is happy, is there any reason for me to look into the cause of the code?
Possibly useful background, November last year the truck got the Bitterroot injectors, turbo, tunes, FRx, in tank mods, intake and exhaust all at once. But like I said since then it has run great with almost 5k miles on the job.
Nope feels great sounds great runs great. I had a dead skip once years ago when an injector connector came apart under the VC and it was super obvious what was wrong.
Since it's running well I'd not worry too much about it.
But I'd prolly fire up the Forscan and watch the PERDELS as it idles. Here's a sample screencap from my truck which runs fine. 8 is always the worst offender due to the way fuel moves thru the head, often near 5%. Greater than that for X amount of time it will set the P0308.
Bumping this one... haven't been driving it that much since I've had my old BMW running but I got froggy and picked up a Motorcraft cam position sensor from Riffraff and popped it in. I cleared my misfire code and it came back after a couple of drive cycles. I swear the idle got smoother and the throttle response improved. I had noticed some slow decline in power and response lately and some black smoke under moderate load which is why I decided to throw a sensor at it. All that got better with the new sensor but the code came back like I said. It's so weird this thing could think its missing at all when it idles this smooth...
Other bright ideas to look at? I still need to try to pull up the PERDELs on forscan. I believe I tried this when I first posted about it last year, but I remember having some kind of issue. Might've been related to not getting oil temp hot enough as my thermostat was stuck open which I fixed this winter. Before that even on summer days my temp gauge on the dash was barely lifting off of Cold now it goes to the normal position in a normal amount of use so it might work now.
Is there a slight flutter in the engine at partial throttle acceleration even though the idle is otherwise nice and smooth? I'm wondering if you have a marginal injector that is causing enough loss of crankshaft speed to generate the misfire code.
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