P0300 after DOD delete

[Tahoeticker]

Hey so I recently installed a stock cam DOD delete kit from Texas speed on a 2016 5.3L Tahoe. When I was in there i put a bunch of new parts on the list includes
New non DOD camshaft
New lifters
2 new pushrods cylinder 6 had a collapsed lifter which I was I did this and when it collapsed it bent a pushrod so I changed both
New gaskets
New timing chain tensioner
New oil pump
New vacuum pump
New fuel pump
Heads were cleaned and decked
New injector o rings
New spark plugs, and wires
The kit came with a Diablo tuner that had a preloaded tune for the vehicle.

When I start the vehicle it has a rough idle and the only code showing is p0300 multiple misfires.

My scanner tool shows that cylinders 5,6,8 are misfiring. 8 the most with 5 not far behind it and 6 is very sporadic. If 8 misfires 800 times in a key cycle 5 might misfire 500 times and 6 will be 30-40.

I did a compression test all the cylinders were around 200psi I tried swapping out coil packs plugs and wires and the misfire stayed with the cylinder. I took the grounds off cleaned them applied dielectric grease and reinstalled. Went thru all the electrical connections. Took off the intake manifold and installed new gaskets on it. I’m pretty much out of ideas at this point.

Does anyone have any ideas on what to look for? Could it be faulty injectors even tho they were fine before I took them out? I’ll be calling Texas speed in the morning.

Any help would be appreciated thank you.

 

[Joseph Garcia]

You've looked at the most common trouble areas already. How about the following?

Vacuum Leaks:

Air leaks in the intake manifold or vacuum hoses can disrupt the air-fuel mixture.
leaking head gasket, low compression, or timing issues can also cause misfires. You can spray brake cleaner or equivalent around gasket areas on the intake and see if the motor rpm's change, signifying a vacuum leak.

Sensor Problems:

Faulty or incorrectly set crankshaft position sensor can affect ignition timing and contribute to misfires. Other folks in the Forum can suggest troubleshooting steps for this.

 

[Fless]

Look up CASE relearn; it's a quick procedure that syncs the cam and crank sensors to each other. It can be done with a bi-directional scan tool. It may or may not be the cause of the P0300 but I recommend doing it to rule it out.

 

[Tahoeticker]

Hey so Diablo Lew recommended doing the case relearn as well my question is do you think it would be throwing a specific code for the cam sensor and not just the generic “random misfire” p0300. The timing chain tensioner was broken. The car had to limp home for maybe 10-15 miles when the lifter collapsed to cause all of this so maybe now it’s out of whack since it’s got a tight timing chain?

 

[Fless]

Any time either the cam or crank sensor is changed, a CASE relearn should be done. Many times a given engine runs okay, but other engines (PCMs) seem to need the relearn. Sensor-specific codes won't necessarily be set. We've had a few members here who have also experienced curing a P0300 by using the relearn. In your case the changed timing components (timing chain tensioner, cam, etc.) may be causing the relational timing to be just enough out of sync to set the code. It's an easy thing to do, no parts required; just a decent scan tool.

 

[intergalactron]

Did you put on an aftermarket valley cover or re-use the old one?

 

[Tahoeticker]

Re-used the old one. I put the valley block off plugs in there. When I plug in the Diablo sport tune it says it can’t read my tcm but it will go thru the steps to upload the tune. Has anyone else had that issue before?

 

[intergalactron]

I just worked on a 2020, your 2016 might be different, but on that 2020 there was a ground strap for each head. Assuming you have them, you re-connected them, right?

 

[Tahoeticker]

Oh yeah took them off scratched them up applied dielectric grease and put them back on. I went thru all the electrical connections I could see and the ones I couldn’t I used my phone to try and see them.

 

[Tahoeticker]

Any chance the pcm went bad? Today I checked the injectors with power and they clicked and I re torqued the rockers in the correct sequence. After all that I got a new code in addition to the p0300… p16a1 throttle body position sensor.

 

[Tahoeticker]

I did the case relearn and I have the same issues. I got a bidirectional scanner that reads more codes. I have the P0300, U0401:71 Invalid data from Engine/Powertrain Control Module I will also get U0401:00 I don’t know what is going on with this vehicle

 

[Tahoeticker]

After doing a running compression test and checking the preload on the lifters I swapped injectors around. Turns out they were clogged. Problem solved. Hopefully this can help someone else.