5.3L AFM to No AFM engine swap Misfire on every cylinder at idle please help!

[VanDamn]

So a 2006 Suburban was brought to my shop after another shop swapped the engine with a used engine that doesn't have AFM. The original engine had AFM. The engine had no power & no inj pulse on cylinders 1,4,6,7. I tricked the PCM by tying in 3157 light bulbs to make it think it still had the AFM solenoids and gained injector pulse on all cylinders and the engine now has power but while idling it misses on every cylinder. It lopes and I can feel it missing. Also under misfire data on my scan tool it shows every cylinder misfiring. If I raise the RPM it clears up or while driving the miss clears up but as soon as it returns to idle the miss comes back. I have also replace the PCM and used a tuner to delete the AFM with no change, it still misfires on every cylinder at idle. Anyone dealt with this before, where should i start? TIA!

[edcmat-l1]

businessman-looking-into-crystal-ball.jpg

[2xLS1]

So a 2006 Suburban was brought to my shop after another shop swapped the engine with a used engine that doesn't have AFM. The original engine had AFM. The engine had no power & no inj pulse on cylinders 1,4,6,7. I tricked the PCM by tying in 3157 light bulbs to make it think it still had the AFM solenoids and gained injector pulse on all cylinders and the engine now has power but while idling it misses on every cylinder. It lopes and I can feel it missing. Also under misfire data on my scan tool it shows every cylinder misfiring. If I raise the RPM it clears up or while driving the miss clears up but as soon as it returns to idle the miss comes back. I have also replace the PCM and used a tuner to delete the AFM with no change, it still misfires on every cylinder at idle. Anyone dealt with this before, where should i start? TIA!

First, a 06 suburban would be a Gen3 P59 controlled vehicle without DOD/AFM so are you sure about the year? Has to be at least a 07. Misfiring at idle on the DOD cylinders is an indication of trying to run non DOD lifters on a DOD cam if those cylinders are actually firing and have injector pulse.

[VanDamn]

Sorry typo, it is a 2007. It is misfiring on all cylinders at idle not just the AFM cylinders. I noticed it looks like the valley plate on the new engine is the DOD delete plate but I'm unsure what, if anything, was replaced inside the engine. If a cam or lifters were or weren't replaced Wouldn't it just misfire on the AFM cylinders or am I mistaken?

[gtstorey]

Is the misfire data on these accurate enough to pick out which cylinders are misfiring if half the cylinders are misfiring? Are the counters showing the same number on all cylinders or mostly on the DOD cylinders. Are the DOD cylinders misfiring causing fueling to get off enough to cause all cylinders to misfire?

[edcmat-l1]

Diagnosis by brail.....

[VanDamn]

I'm not sure on the accuracy part but it's sporadic. Its shows all cylinders missing at different rates & on misfire history it shows non AFM cylinders 3 & 5 having the most misfires.. I just don't know if I should be looking into engine mechanical, or AFM electrical, or which direction I should go to diagnose it. I've checked the normal, fuel, spark, vacuum leaks etc. & everything seems okay. I'm just thrown off because it all started with the AFM cylinders which originally had no inj pulse but after tricking PCM and later tuning it out it it has pulse and now engine power but just missing only at idle.

[gtstorey]

Someone has been hinting to post a tune and log so you might consider doing that.

[edcmat-l1]

Lemme get Stevie in here to take a look.

[VanDamn]

I kind of got that hint but I removed the tune because it did not make any difference. I did leave the new ecm in the truck & I can post PID's from my scan tool or re-tune it and upload that if it will help but the tune had no effect what so ever so I removed it. Is there anything else that I can post to make it easier to help with this? I personally do not think it has anything to do with the PCM or Programing but I just am not sure so that's why I'm here posting. What can I do to help you guys to help me?

[gtstorey]

What can it hurt to post the as run tune? Probably asked for to confirm what actually done to disable the AFM. And log is about all anyone can review to see how the truck is running. There is a limit what can be done remotely other than throw out guesses. And for the most part the more experienced people on here won't just guess blind (as in Stevie Wonder).

Other than that it's back to the basics of fuel, spark and compression. And maybe add in wiring to that list.

[edcmat-l1]

What can I do to help you guys to help me?

It's already been said. Post the tune file and a corresponding data log.

[2xLS1]

He said he used a "tuner" do delete the AFM. I'm going to guess he used something other than HP Tuners and can't post a HPT file. There are other products out there that will delete DOD/AFM.

[2xLS1]

I kind of got that hint but I removed the tune because it did not make any difference. I did leave the new ecm in the truck & I can post PID's from my scan tool or re-tune it and upload that if it will help but the tune had no effect what so ever so I removed it. Is there anything else that I can post to make it easier to help with this? I personally do not think it has anything to do with the PCM or Programing but I just am not sure so that's why I'm here posting. What can I do to help you guys to help me?

Did the new engine come with it's own injectors or were the ones from the original engine used? Different 5.3L engines could have different injectors.

[gtstorey]

He said he used a "tuner" do delete the AFM. I'm going to guess he used something other than HP Tuners and can't post a HPT file. There are other products out there that will delete DOD/AFM.

You aren’t doing much to help anyone help you. At least try and read the file. And post a log as anyway.