Desperate help/ only vehicle

[Marky Dissod]

You mean know how to turn off misfire monitors? There is no spark or fuel by cylinder tuning on these platforms, so I don't see how it can be tuned for it.
The issue is an imbalance in events because of different lobe profiles on the dod cylinders.

There are misfire sensitivity tables that can be desensitized.
Don't know if those tables are available after HPT Version 2.4?
They're available to the older tuners who got OBD2 TunerCAT before it got sold to 'JET'.

 

[hagar]

There are misfire sensitivity tables that can be desensitized.
Don't know if those tables are available after HPT Version 2.4?
They're available to the older tuners who have OBD2 TunerCAT.

Yeah they still have that. Is it knock frequency calibration vs cylinder, or a blanket sensitivity vs rpms and grams per cylinder load?
I can see changing the frequency calibration for the dod cylinders only to compensate for the misfire, but it is still ultimately misfiring because of a mismatch between the lifter specs and the cam specs.

I still have unlimited tunercat obd2 from when it first came out. Was planning to fire it back up and update to save money on some tunes. I have not used it since lile 2006 so I am excited to see what is different.

 

[Marky Dissod]

Couldn't say off the top of my head - I've SEEN OBD2 TunerCAT, but I wasn't the one using it.
If it's unlimited, THINK John still updates it ...

 

[mikez71]

It's POSSIBLE to tune for this, but the tuner has to know how to do this specifically.

NO, I don't think you can tune for wrong lifters..
For one I think AFM lifters are longer, base circle maybe smaller. Possible for longer pushrods to compensate maybe?
But easier to just get 1 AFM lifter if the tool doesn't work or you want more peace of mind.

Making sensitivities lower won't help anything unless you are getting FALSE knock/misfires?

Here's what I could find for individual cylinder tuning regarding fuel/knock/misfire..
No individual cylinder misfire, probably a calculation of crank position, ignition timing, and rpm?

 

[West 1]

In the GM computer if connected to a bi directional scanner that can read the GM codes there is a simple option. It says. AFM Equipped: There is a YES and a NO answer. If you click NO the computer will no longer look for any AFM data it will now treat your engine like a Non AFM engine from that point on. The hard part is finding someone that knows how to do this in the GM computer.

At 340,000 miles the engine has given you a very good life. Releasing the stuck lifter with the Tool available will not make anything new. It will release that one lifter and you are back in business but still have an engine with 340,000 miles on it.

At your mileage anything could break at any time so for me this is a no brainer. Use the tool, release the lifter, shut off your AFM and get back on the road.

If money is tight this is a 100% repair to get back on the road. It works and is so much faster and cheaper than pulling the heads. Good luck with whatever you decide.

 

[Marky Dissod]

Why am I the only one NOT typing a word about 'individual cylinders'? Not about to start now.

What I AM saying is to desensitize the misfire detection to the point where it does not care about the difference between AFM vs non-AFM.
Obviously this makes misfire detection nearly useless. What would happen if every value in table 14005 was raised to 1,760?

 

[West 1]

When a lifter fails in the down AFM position you are way beyond a misfire. You now have mechanical failure. The lifter has maybe 1/2” of slop, the push rod is banging against the loose rocker arm and if yo continue driving it will damage the camshaft. Dealing with the misfire is far down the list on this repair. It needs a mechanical repair first.

 

[Marky Dissod]

When a lifter fails in the down AFM position you are way beyond a misfire. You now have mechanical failure.
The lifter has maybe 1/2” of slop, the push rod is banging against the loose rocker arm and if you continue driving it will damage the camshaft.

If it's not already damaged.

Dealing with the misfire is far down the list on this repair. It needs a mechanical repair first.

Agree without reservation.

 

[hagar]

Why am I the only one NOT typing a word about 'individual cylinders'? Not about to start now.

What I AM saying is to desensitize the misfire detection to the point where it does not care about the difference between AFM vs non-AFM.
Obviously this makes misfire detection nearly useless. What would happen if every value in table 14005 was raised to 1,760?

Obviously just adjusting the entire misfire detection would work, but then you don't have a properly functioning misfire system.

I would never run a dod cam with non dod lifters, but if I was forced to do so, I would still try to keep as much of the misfire detection functionality as possible. Even if you fudged the numbers enough to stop picking up misfires, only on the 4 dod lobe sets, it would still leave 4 that are operating properly.

Its a dumb idea either way. If someone is going to pull a head and not do a dod delete, might as well just throw in another dod lifter and carry on with life.