'07 Envoy LH6 to L92 swap - need help with tuning

[Wild Customs]

I need help tuning my L92 swapped Envoy.

I found the L92 had DOD lifters (but with a normal valley cover?!?!) so I just switched those with LS7 style lifters, and swapped over the front timing cover & cam sprocket from the 5.3L to the 6.2L to delete the VVT and used the same stock cam.

Now after fitting the L92 in I had a friend interchange some tables in the tune from the file of the vehicle we took the engine from to my Envoy E67 tune file.

Now my main problem is I'm having misfiring at idle and the O2 readings are all over the place and I can smell fuel from the exhaust. So far I've swapped out the coils, plugs, wires and even injectors and still doing the same thing.

Using Launch scanner I can see the misfire is coming from the DOD cylinders. After doing a compression test found the DOD cylinders to be around 50 PSI less than the normal ones. DOD: ~130 PSI non-DOD: ~180 PSI

I need to know what exactly is wrong so I can fix it. If someone more experienced than I am could have a look at the files and tell me where it went wrong I'd appreciate it.

Whenever the misfire is there I'm getting harsh shifting in the transmission as if it's commanding full oil pressure.


Appreciate any help I can get

[kevin87turbot]

You can't just change the lifters to a non-DOD lifter style on a DOD style cam. The difference in the lobe designs will cause low compression on those cylinders, as well as misfire codes. You'll need to change the camshaft to fix this issue.

[blindsquirrel]

The lobes for the DOD cylinders have very loooooong clearance ramps that gradually take up the internal lash inside the DOD lifters between the locking pins and the lifter body. With standard non-DOD lifters that internal lash is no longer there, and those long ramps are now opening the valve instead of just taking up internal clearance. A non-DOD camshaft has non-DOD lobes with normal hydraulic roller open/close ramps on all cylinders, since all lifters are non-DOD and don't have internal lash that needs to be accounted for.

[Wild Customs]

First of all I'm not even sure why it had the DOD lifters in the first place, as it had the normal non-DOD valley cover and AFAIK the '07 Yukon 6.2L came with VVT but no DOD, which is why I thought taking them out would be a good thing.

Secondly, it might be just me but it seems like it runs smooth before the O2 readings get into play and start adjusting fuel.

Lastly, can the hard shifting (full trans oil pressure) be caused by the misfire? if I raise the RPM over 1.5k for a while until CEL stops flashing it seems to shift normal after that, and shifts hard when CEL starts flashing.

Other than the cam, do you guys see any mistakes in the tune file?

Also would it be a bad idea if I use this stock non-DOD cam p/n 12689035 or would it rob power from the engine?

[blindsquirrel]

It has the miss at idle on 1-4-6-7 because valves on those cylinders are opening way early and closing way late, as evidenced by your cranking compression numbers. The easy fix is to put the DOD lifters back in.

[Wild Customs]

Yeah but replacing the lifters includes removing the heads, replacing the head gasket again, buying new lifter trays, and a bunch of seals and so on.. while on the other hand I could swap the cam and be done with it.

Now, will this cam 12689035 work fine on the 6.2 or should I be looking for something else?

[5FDP]

GM decided to make the L92 that way to save money, if every engine is the same except the valley cover it saves on cost. Then it's just a programming thing to have it never come on.

Yes, that camshaft will work.