Misfire! P0306 - dropped valve seat!

Need some help folks,

Yesterday truck was driving normal and went to pull out on highway at about 3/4 throttle hit 60mph and lightly let off the gas and truck started shaking violently. Check engine light started blinking so pulled codes p0300(random misfire), p0305 and p0306 (cylinders 5/6 mifire).

Got it towed home and just put in new spark plugs (NGK LFR7AIX-11/ 2309 supercharger approved) and swapped ingnition coils and still getting the same rough engine shake and misfire codes.
Is it possible to blow the head gasket on both banks on the backside at the same time? Coolant is full in radiator and looks normal, and engine oil looks smells normal. Hopefull I can do a compression test with the supercharger in the way on the driver side. Any other suggestions?



Here's the plugs from cylinders 5 and 6 they look normal not wet.

 

You might start by swapping the coil packs around on the passenger side since theyre easier to access and see if the code follows. The plugs look okay to me

 

Forgot to mention that I did swap coils on both banks and misfire did not move so it seems coil packs are good.

 

What are you using for tuning?

 

running UCON last 3 years.

 

You may do well doing a pressure test on the cooling system and a compression test as well. I was able to do a compression test with the blower on, on my truck. But anyways, i would be suspecting of the UCON if those both come back with passing tests. I had issues with the UCON on my truck at one point and it had to be replaced. I would start by trying to narrow it down one thing at a time though

 

How long did you run the ucon before it started giving issues? I assume you shipped it back to urd and they diagnosed it?

 

I had issues from day one and i fought for 6 months to diagnose it with the help of urd and members on here. Finally narrowed it down to the ucon and then sent it to urd and they replaced it.

 

I see, well I need to do a compression test and or leak down. Should I just skip the compression test and do a leak down? You have any tips to find top dead center?

 

Had this happen to me, not too long ago, with cylinder 3, turned out to be injectors, I swapped injectors and it changed cylinders, hand it cleans and repairs by fic and still the same, finally replaced all my injectors with injector dynamics injectors and misfire gone, worth a shot to swap injectors and see if misfire changes cylinders

 

compression test (cold throttle wide open ).......leak down ( cold 100psi ) test can tell U definitively very different issues

Im NOT familiar with a ‘ UCON ‘ tune................the plugs shown are running rich

any tune other than stock truly matters matched to the type o driving environs
( not sure why a tune was necessary )

not sure IF most of Ur driving ............In town commute

or mostly hi-way legal speeds

the plugs shown are running rich

wires + coil paks is where i would start

 

After pressure test and leak down if everything checks out I’ll pull the blower and swap injectors. Funny my Depo fuel pressure gauge stopped working a month ago. It’s pegged at 47 psi. First depo guage lasted a year this replacement lasted 2. Don’t buy Depo guages

 

UCON ALL DAY!!
If you got 455 injectors then take out the Ucon and run the TRD Tune. Watch your problems disappear

 

Yes still using 455 injectors. After doing an injector swap I'll see, been running ucon 3 years no problem until now. Maybe upgrade to injector dynamics.

 

TRD injectors are pretty solid. You’re lucky the Ucon lasted that long with no problems

 

Ucon hardware or software issues? If injector swap doesn’t show anything - will try to send ucon in for diagnostics. Then look to TRD tune the ecu. Doing comp test and leak down tomorrow.

 

UPDATE! After compression test and leak down test I’m screwed lol!

0 compression on cylinder 6 and leak down test shows lots of air escaping out of the intake. We’ll see from here

 

what does #6 plug look like

zero =

broken stud/bolt upper intake

stuck or bent valve

bad ring stack on piston ( not likely to hear intake side )

bad head gasket ( maybe not likely )

air escaping out o intake could be 1st 2.............nothing beats a tear down tho

 

Researching online for rebuilt head. Found ADV Cylinder heads in California. Going to reach out to them , will keep everyone posted.

 

U havent said whats wrong with the current head.......................

what did U find ????????