Had cyl 5 head gasket burn out. Installed head from a lower mile vehicle (approx 80k). Had it machined to make sure it was flat. Block deck was ok. No cel but could hear pfft pfft.


Went ahead and ordered new aftermarket injectors as the ones I have the little plate on the tips are brittle and used most of my spares a year ago.

Upon reassembly she does fine at idle but once you get past 30mph throws a cel and it blinks.

Same cel for #3. Swapped plugs. Swapped plugs wires. Swapped injectors. Can't feel a miss but cel still came back

Just to be 100% sure a miss fire Cel has to come the ignition side.

The maf, injectors and coil pack are all less than 2 years old. Maf and injectors are Bosch. Coil packs are cheap Amazon.
Had no issues before tear down. Just wanted to make sure I am likely looking at either a pin issue at the coil pack or a coincidence coil pack breaking down and losing spark under load on #3.

Engine has no noticable loss of power or feel any miss.

Thanks ahead of time.

 

Maybe check compression first. Compare to all cylinders to verify valves are sealing well.

 

I will double check although being a center cylinder if there was blow by at the head gasket I'd have the audible pfft pfft pfft like her sister cylinder did before the head gasket job. This blow by was not enough to destroy the head gasket but was passing to either side of it. What's troubling as it was a large blow by but no cel. It was loud enough that the lady driver pointed it out to me


This is why I was wondering aloud if a mechanical failure could cause a misfire cel.

 

Photo

of low mile head before cleaning/machining.

 

Phot

Photo of head removed. No sign of coolant blow by of liner so unless it suddenly gave way I wouldn't believe that's the issue. I pulled the valve cover to inspect the movement of the valves. I don't have a compression gauge at the house but will do a leak down test on the cylinder shortly

 

Swap coils left and right and see if it follows. BTW, you might be interested in this: https://extinctmotorsports.com/the-e...g-perspective/

 

found my culprit, exhaust valve isn't seating fully. Really should have torn down the head or at least filled the head with acetone/gas to verify the valves were seating. The intake side valve holds just fine.


Did a leak down test on it and could hear air out the exhaust. I don't have proper tools at home so got this off with a big c clamp. Will have to drop by the shop to get cutters and lapping compound tomorrow.

 

I’m glad to hear that you found the cause.

 

Got head back to the shop this morning and did what I should have done to begin with, 3 angle valve job. As I finished each one I put a few ounces of rubbing alcohol in each port to verify they retained fluid.

The head is now installed for the 2nd time and cold compression is 115 to 120. No idea if the compression gauge is accurate, all I care is they are very close range.

Fingers crossed she's reassembled in the morning and back on the road by lunch time.


The owner I got the 03 parts rig with 8x,xxx miles said the engine had jumped time. Due to the low miles I figured the heads just needing decking was a sure bet. I wonder if I have a good low mile 4.6 sitting here and the issue was just carboned up valves from running with bad 02 sensors and/or cheap fuel for an extended period of time.
​​​​​​

 

Maybe it’s good and you’re driving it now?