The ZHP swap I put into my wagon at 184,000 miles and some change. It was running perfectly fine in the donor car before it was pulled as I drove that car so I know.

Now that it is in my wagon I'm having issues with a misfire cylinder 5 very consistent and it only happens if I go wide open throttle above 3,500 to 4,000 RPMs...

I can tell when it's going to happen because when I go wide open throttle there is a loss of power and a very audible noise that sounds like a rattling or pinging. I'm inside the car The sound like it's coming from directly in front of me in the intake manifold area.

if I keep pressing through and letting the noise occur then the misfire will occur and the car will idle roughly until I turn the car off turn the back on.

If I drive the car staying below 3500 RPMs just cruising around it's fine. And idles perfect it even passed emissions because I was able to complete the drive cycle in about 30 minutes because everything is kept blow 3,000 RPMs.

Things that have been changed on the engine before I swapped it in are:

CCV system
Intake manifold gaskets
Throttle body gasket
Oil filter housing gasket
Valve car gasket and spark plug gasket set
6 brand new NGK iridium plugs gapped .32
M3 fuel pump
New mann fuel filter
Lower intake boot


It was at this point that when I got my swap done I passed emissions got my drive cycle done and then when I wanted to go for a spirited drive that's when I figured out the problem.

I pulled the iridium plugs and saw that cylinders 1 2 and 3 look perfectly fine..cylinders 4,5 and 6 look rich with 5 and 6 being the most carbon deposit heavy.

I pulled both pre-cst O2 sensors and bank one looks just fine but bank too looks very white as a there's a lien condition.

So I'm not sure why bank 2 cylinders 4,5 and 6 spark plugs look rich but the associated oxygen sensor for that bank looks extremely lean or white maybe fouled out

Also I fired up INPA and check to the lambda short-term and long-term trims and saw the bank to lambda was sitting at a -8 value and never moved..

Things I've done so far that if not helped and I still have the same exact problem are:

-Change to another known good fuel pump
-Change the fuel filter again
-Swapped in 6 good coil packs from my S54 engine which are the same coil pack part number as m54
- installed six brand new NGK double platinum plugs
-installed two known good PreCat O2 sensors and bank 1 and bank 2
-Pulled the disa valve verified the pin was still there the flap was good there was no play That's functioning properly Even resealed it with some gasket sealer to see if maybe there was a small leak somewhere...
-cleared every single adaptation value using INPA

After all that said I'm done put everything back together and does the same thing. Same exact thing no change.

My attempt to do a compression test tonight and that didn't go the way I wanted to. I purchase a compression tester from O'Reilly's that was a Bosch unit... And the unit is defective. As soon as the needle goes all the way up to 160ish needle starts dropping down all the way to zero and it's not holding pressure. went to a friend's house to borrow his compression tester in his was broken too The needle wouldn't even move.

So scratch the compression test for now until this weekend I'll have to get another tester.

So right now in my mind I either have what I think is a very bad intake leak somewhere maybe a crack and take manifold or a pinched gasket maybe...

Or I think bank 2 catalytic converter is clogged possibly.

I know it's a lot to read I'm going to post some pictures below of my spark plugs my O2 sensors before they were swapped and my screenshot from INPA showing my field trim

Maybe some M54ZHP gurus can give me some more direction or their thoughts or maybe confirm what I'm thinking.

In the pictures of the spark plugs the order of cylinders is 1 through 6 left to right. 123 look good 456-Rich.

In the pictures of the oxygen sensors the dark one is bank 1 and the white one is bank 2.





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