persistant misfires after many componets replaced
 

Ive been busy sorting out various things on my rig, seems when I address one problem something new pops up. The misfires have been a problem since I picked up the truck in late January 2016. Ive replaced several componets commonly associated with misfires. But its worth mentioning that along with a new reman block from Turner, I had my mechanic install new champion spark plugs, magnecore ignition wires, Bosch front o2 sensors etc. I replaced the plugs and wires again afew months later along with a new set of AllMakes4x4 ignition coils. Engine still misfired. Fast forward to the present, last week I replaced the spark plugs for a third time, made sure they were at the proper gap spec, ensured the ignition wires were tight and coils were in good. Next I replaced all the fuel injectors with a set of reman Bosch genuine injectors. Today several pending misfire codes popped up on the ultra guage. Im gonna drop the truck off at the shop next week AGAIN for another look over but Im completly at loss. I will be reaching out to Turner as well.

Any thoughts?

Hi TRIAR,

Just a thought, what about the lamda O2 sensors or wiring to them in the exhaust? Have you read the codes? it might give you some clues. It sounds as though you have replaced all the potential cuprit parts but 'sods law' it still happens. Try reading the codes and hopefully all will be revealed. Last but not least is an intermittent fault on the CPS although generally they work OK or fail completely but it may just be the wiring to the CPS is defective.

[QUOTE=OffroadFrance;587583]Hi TRIAR,

Just a thought, what about the lamda O2 sensors or wiring to them in the exhaust? Have you read the codes? it might give you some clues. It sounds as though you have replaced all the potential cuprit parts but 'sods law' it still happens. Try reading the codes and hopefully all will be revealed. Last but not least is an intermittent fault on the CPS although generally they work OK or fail completely but it may just be the wiring to the CPS is defective.[/QhUOTE]

Not sure about the sensors but all have been replaced since January. The crankshaft position sensor was replaced a few years ago after the old one failed. We a pain in the ass to replace...

[QUOTE=TRIARII;587584]recheck the codes again. I have replaced front bosch O2 sensors 3 times in few months. They fail a lot. Get it from advance or auto zone because they waranty them. its good that you can return them until you get it straight.

were the heads redone when you replaced the motor?

I know you said misfires, but could you please report exactly what codes you are getting?

During engine swap the heads from my old block were machined at local machine shop. Front 02 sensors were replaced with Bosch. Then one failed so I replaced again with another Bosch. Rear 02 sensors are proline. In my experience faulty O2 sensors trigger a lean O2 related trouble code. Ive had them in the past but all were resolved once sensors were replaced.

Codes:
P0305= cylinder 5 misfire
P0306= cylinder 6 misfire
P0303= cylinder 3 misfire
P0300= random multiple cylinder misfire

The cats do not glow red. The CEL does not flash. Engine temps do not exceed 209 (average 197-203). No apparent fuel odor or fuel leaks. No visiable coolant leaks.

According to datastream
Fuel trim a = 1.00 :1
Fuel trim b = 100 :1
Idel air = 100.96 kg/h

You figure this out!
 

SO the heads were machined but were the valves and seats redone?