4.8 to 5.3 misfire cylinder 1,4,6,7

[akalshaikh]

Hi,

Title says it all. customer swapper out his 4.8 to 5.3 from gen 4 to gen 3.
He changed reluctor wheel from 24x to 58x, all new llifters, non vvt cam (stock), springs, pushrods, valley cover & timing cover.

car misfires at idle only in DoD cylinders although vvt & DoD are tuned out.

I searched the forum and many faced the issue though no one posted the solution.

any input will be much appreciated.

[akalshaikh]

Bump!!!

Anyone??

[Alvin]

It looks like its done right to me.. IDK

[5FDP]

Non VVT camshaft does not mean non AFM/DoD though. So if you just installed a non VVT camshaft but still a AFM camshaft you will always have misfires.

[Alvin]

Non VVT camshaft does not mean non AFM/DoD though. So if you just installed a non VVT camshaft but still a AFM camshaft you will always have misfires.

didn't notice that.. Yeah its got to be a non DOD cam.

[SiriusC1024]

You didn't set the intake and exhaust camshaft minimums to 0. They're still stock at 2 degrees.

[akalshaikh]

Will do,, will see if it changes anything thanks

[SiriusC1024]

Thing is gen III doesn't have a cam phaser, so I'm doubting if what I mentioned will help. How come you don't copy over the settings from a gen III 5.3? The spark tables, knock sensor gains, fuel injectors, etc. are totally different. Negative low octane timing at WOT from 4400 to 5200rpm? Throttle area rate limits are really low in 1st gear. Torque limit vs rpm vs gear is low, too.

Whatever is gen III set for gen III.

[akalshaikh]

Thing is gen III doesn't have a cam phaser, so I'm doubting if what I mentioned will help. How come you don't copy over the settings from a gen III 5.3? The spark tables, knock sensor gains, fuel injectors, etc. are totally different. Negative low octane timing at WOT from 4400 to 5200rpm? Throttle area rate limits are really low in 1st gear. Torque limit vs rpm vs gear is low, too.

Whatever is gen III set for gen III.

I actually tried that and it didn't work. I copied what ever I could from a gen 3 to gen 4 E38 but again nothing.

The issue is there only in idle ince you rev it up misfire. Once the rpm drops after revving it the car dies or drops to 300 rpms.

[akalshaikh]

Non VVT camshaft does not mean non AFM/DoD though. So if you just installed a non VVT camshaft but still a AFM camshaft you will always have misfires.

The camshaft was out of a Gen 3 5.3 truck. No DoD, AFM or VVT

[SiriusC1024]

Have you done a crank relearn and throttle cal yet?

What year 5.3 and what all sensors aren't gen 4?

[verlon]

Have you sealed DoD oil control passages in the block?

[blindsquirrel]

Gen 3 block does not have the DOD oil passages.

[SiriusC1024]

I have a suspicion that the misfires that "many faced" have to do with the different location of the knock sensors and sensor gains. What's making it worse it that it's not tuned for that specific gen 3 engine. Look at what the O2 sensors are doing and the erratic spark.

[verlon]

Gen 3 block does not have the DOD oil passages.

This misleaded me...

customer swapper out his 4.8 to 5.3 from gen 4 to gen 3