I have a 97 f150 with a cylinder 1 miss that keeps registering as a code but never bucks if you switch to a higher gear or pull over and watch cylinder contribution on my snap on scanner. The only symptoms are basically the check engine light blink.

The coil, plug,and wire have all been replaced multiple times by the owner.

The truck has a f75f-12a650-arc computer I have a f75f-12a650-lb available to me to use as a test computer but it is from a f250. Both trucks are 4.6 5speeds

From what I have gathered they are both federal emission computers that the only diff i can find.

For the purpose of seeing if the trucks computer is bad by swapping the 250 ecu, should everything be ok??

 

I would think the swap would work based on what you have.
You should know how a misfire is detected .
The front crank sensor times crank rotation for each cylinder every time a cylinder comes up in the fire order.
If the rotation time is too slow and falls outside the average for all 8 cylinders, the code is set as a 30x code after it happens enough time to exceed the program threshold for failures..
A loss of ignition to the cylinder for any reason, loss of fuel injector operation, fouled plug, leaking head gasket or any cylinder issue that could cause that cylinder to produce less rotating torque thus rotate slower will be considered a misfire.
.
If however a PCM coil driver fails in the PCM, this is not a timed diagnostic function but a power monitor circuit function.
A coil driver failure is coded as a 35x code.
If your code is a 30x code I would not think it a PCM issue involving only one cylinder and not all eight for basic cylinder timing.
A single coil driver can be a source of a single cylinder issue.
Just some background for you to know about.
Good luck, let us know what happens.

 

I switched computers early yesterday morning and went for a drive with no success. The light started to blink for cyl 1. Nothing felt and nothing registering on cylinder contribution. I am going to swap 1&5 injectors when i get some free time.

 

The blinking CEL indicates a Type A misfire rate.


Will your Snap On scanner let you look at Mode 6 data?
Specifically TID $53 CID $00 to see the number of misfires on cylinder #1?

 

No miss is registering on contribution test while light blinking pulled off on the side of the road.

I swapped computer with the same code return/symptoms.

It has a new tune up just now

I guess test 53 isnt availible this early in obd2 my list stops at test 52

Went on drive after tune up and same result. Gonna swap the injector.

Could it be weak cam/crank signal causing the speeds to be out of spec and then throwing the light???

 

A flashing CEL tells you the cylinder has lost ignition.
.
The reason is the unburnt fuel as injected is passing through to the CATS where it can burn and melt the cat structure, then you have extra repair costs.
.
This would tend not to be an injector issue.
Cam position sensor controls injector timing only.
Good luck.

 

I know the flashing cel definition is catalyst damaging warning. The truck has no miss feel

Injector swap was unsuccessful. If this helps anyone help me. The light doesnt come on til cruising at 60 in 5th gear and then it goes on the blink fest. Pulled over or light accel from being pulled off. Once it has set it tends not to blink again

I guess i can try yet another coil.... I have swapped the plug and injector to diff cylinders since the original post

 

Cruising speed miss is usally egr related but wouldnt that effect more than 1 cyl?

 

Same symptoms with egr vacuum line unplugged.... So its not egr valve miss at cruise

If i could get it to be consistent and actually miss that would be awesome.

Im leaning towards cam and crank sensors. I have them availible from a core that i am waiting for a new reman engine to arrive.

If it was mechanical it should stay missing and continually blink even if i cut the key off and back on. It stores when keyed off while rolling down the road

 

Contribution test - is that a cylinder balance test?


What does the Mode $6 data show for all cylinders?

 

The CEL flashing is done when a misfire detection occurs along with the OX sensor detecting the extra oxygen from lack of combustion in that cylinder.
A clever software hardware combination put to good use.
Good luck.

 

Yea contribution is used to id non firing at idle

Mode 6 i have no test 53 to id the cylinders

 

Swapped in a used cam sensor/ no change. Still misses at almost the same spot on the road. I have to drive out 5 miles from the house and it is after getting up to speed around 60 in 5th gear and topping a hill after adding a little fuel to top the hill then the light triggers.The Data doesnt show a change in Bank 1 from Bank 2 to indicate that there is an actuall miss.. Its showing a change on both banks

 

At the miss the 02 readings are the same and then change back to switching but the data pid is still showing its missing...........

 

The only thing I know to do next would be to pull the a/c compressor and swap in a crank sensor....