misfire code, getting CEL to go off

ab_slack · Apr 21, 2015

99 Ranger with 3.0L

Had a cylinder 6 misfire code. The misfire was quite evident when driving when it showed up.

The wire was bad for that cylinder. Opted to replace all wires. Drivability issue solved.

The vehicle has an overdue inspection. No big deal it is just an emissions test that they will do by connecting to the OBDII port and if the OBD says emissions are good then good to go.

My problem is that since it is overdue I want to drive it as little as possible since it is possible to get ticketed for driving with overdue inspection.

At this point am I better off letting the CEL go off on its own thereby indicating the only issue that was present has been resolved? Or manually clear it which will get the light off but then I need to wait for all the monitors to run.

Which of those two scenarios will take less driving?

Manually clearing it has the advantage of giving rather quick feedback if the misfire is unresolved. At the moment I am assuming that since the drivability issue has been resolved that the misfire is probably resolved.

RonD · Apr 22, 2015

Usually unhooking the battery for 5 minutes will clear CEL, it also clears "learned" engine parameters so engine may idle funny and act differently for a few drive cycles, not bad just not as expected until it relearns the engine sensors.

I did read some 1995 and newer EEC-V computers would turn on the CEL if battery was disconnected and then reconnected, this prevented people from clearing CEL just before emissions test, but never seen that myself.

Who read the #6 misfire code for you?
Just go there and have them clear it

ab_slack · Apr 22, 2015

I have the tool and read it and yes I could clear it.

My question wasn't strictly how to clear it. It was which was faster,

1) let it go away on its own at which point it is ready for inspection.

2) Reset it and wait till all the diagnostic monitors to run.

The state inspection recognizes when a reset has been recently performed and won't pass. So you need to wait till they run. Whatever number of drive cycles and conditions. Just don't know which of the scenarios is quicker.

Had the experience once with my daughter where the monitors didn't complete after reset for two weeks. Mostly because it was winter and in the short drives she did it never warmed up enough. We specifically had to take it out on the highway and make some long drives.

Probably wouldn't happen now, not this time of year, but with inspection already overdue I want to minimize the amount of driving,

RonD · Apr 22, 2015

I think Ford needs 3 drive cycles of at least 30min each time to clear misfire code.
There is no "timer" so I would read that as warmed up

When misfire(s) are set as hard codes(CEL) the computer stores the RPM, load and engine temp when misfires happen, those parameters must be similar and without misfires for at least 3 cycles for the CEL to go off.

Also found this:
Misfire & Fuel Monitors - From a stop, accelerate to 104 Km/h (65 MPH). Decelerate at closed throttle until 64 Km/h (40 MPH) (no brakes). Repeat this 3 times.

This may clear misfire code quicker, assuming there are no more misfires

enjr44 · Apr 22, 2015

There are folks here with a lot more knowledge than me; but, I thought a misfire code was a hard set code and will not go away by itself. It just sits there until it is cleared by resetting the computer.

Rearanger · Apr 22, 2015

I would phone the inspection station and discuss your best option before you clear the code. They'll probably be most helpful.

RonD · Apr 22, 2015

It would depend on the code, Emissions codes can stay along time, computer records and sets codes all the time, soft set, in the case of misfires it needs to happen a few times before CEL will come on and stay on, hard set, it will flash during misfire but that doesn't always mean CEL will stay on after that.
And according to what I read the OBD II misfire code will reset, CEL goes off, if engine is repaired and misfires no longer occur, as said above after 3 drive cycles, but I have never had to do this so just speculation on my part at this point.
Codes will stay in history

CEL is a warning to driver that there is a problem, and it might have been a "cash grab" in the past, lol, but the computer can recognize that a problem no longer exists so should reset the CEL, maybe just wishful thinking on my part.

ab_slack · Apr 22, 2015

Thanks for all the info. I will see what happens. It isn't getting to 65mph. The misfire was present for a full drive cycle so may be more persistent than if it was discovered and corrected right away. Vehicle wasn't at home.

I know it will clear. I recently went thru this on my 2002 Explorer when it spit out a spark plug. I ended up driving that several miles with an open cylinder to get home. Misfire code of course because well there was no spark plug.

After doing thread repair putting new plug and coil pack the CEL went away pretty quick. But I drive the explorer and it sees lots of incidental use including some highway. I am not the one that drives the ranger so it sees an entirely different driving pattern and usually not as much highway.

Third cycle for the ranger should be tonight so we will see.

Thanks.

ab_slack · Apr 22, 2015

It cleared tonight so we are good. Thanks

csargents1546 · Apr 23, 2015

The code will stay in memory as a "cmdtc" Two ways to get rid of a cell, disconnect the battery or using a scan tool. The latter is preferable since it will not clear your KAM and adaptive tables. To date I have not seen a cell from disconnecting the battry alone. Some may set a code but not turn on the cel.

misfire code, getting CEL to go off

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