Okay I can do that. I had the flex plate off overnight so I kept it on the kitchen table, to wife's consternation. So I know it is flat. And you may recall that I had one disintegrate. Recently. So I gave it a good visual inspection and saw nothing amiss. It is the same flex plate out of the 4.0. The only difference is that I removed the spacer ring on the inside because I have different flywheels. I'll open up the inspection hole and check it out.

 

Just a thought, your cam determines firing order, it could be possible Crower miss picked or mislabeled the cam they sent you and you now have an engine with a different firing sequence. If you've done all the other stuff you could pull your rocker covers and find your firing order and double check it against what it's supposed to be. From there, if it is incorrect it may be as easy as switching leads at the coil packs.

 

Somewhere a tech is cursing me out for sharing this information, but here it goes. Remember, you need 4 basic parts to have an ignition cycle, Suck, Squeeze, Bang and Blow.

Swap plugs with the cylinder next to it. your misfire moves, its the plug.

That fails and misfire stays, swap wires with the opposite bank. (that way you have the same length wire to the spark plug. Misfire moves, its the wire.

That fails to work, its much harder to do on this as opposed to a single coil on plug setup and the next step would be to switch coils. If it moves, then its the coil pack itself.

That fails to work, you check fuel pressure. Not just cold, but also while hot. Pumps do tend to like dropping in pressure after they heat up (generally speaking). But its probably not a fuel problem because it would be across all cylinders.

That fails to work, you would move onto compression. Which you have already done.

That fails, you then look at the other factors ,engine management, vacuum leaks, coolant leaks, the flex plate you installed and was warped because you put it on with an impact gun (joke), uprated cam, etc etc, yada yada yada.

This is the diagnostic flow chart for a tech chasing a misfire.

 

I'm wondering if the 4.0 ECU is to lean in closed loop?
But I've never heard of anyone else having this problem after the 4.6 swap.

 

Just curious, in a short sentence or two, what the heck's a flex plate anyway?
I've been nodding and pretending I knew the whole time, but I was faking it. I can't take the shame anymore. :-)

 

From the back of the engine it is flywheel (weighted wheel with starter gear around it), then flex plate (thin disk of metal as large as the flywheel. Bolts to the flywheel), then torque converter (heavy mushroom looking part that contains transmission fluid. Bolted to the flex plate), then transmission.

 

Thanks for that. I've been assuming everything was good because it all worked on the 4.0. But the 4.6 pistons are lower compression, so if something was marginal, it could cause a problem. I should have swapped the pistons, too.

But I am going to try the whole flow chart tonight. I'll report the results.

 

That cam. Yes it does indeed concern me. But the 229 is land Rover specific and it is actually another cam (Buick 300) with the nose machined for our timing gear. So they would have had to make the absolute wrong one, then machine it. I wish I'd just gotten a stock cam (but I may dispense that wish if it all works). I don't think it is the cam, but anything is possible.

I still have the original cam if it comes to it. But I'd have to be pretty discouraged to swap that old beater in.

 

Thanks, the flex plate was the only one I was not familiar with. Never heard of one.

 

No problem, Jamie. I knew you knew the other from other threads. Just describing its location.

I'm actually glad you asked because I found a picture of mine on the old engine.



I have to find the date on that picture. That may be the one that disintegrated. The empty holes are the bolt holes for the torque converter. Putting those bolts in with the engine on (only way I know to do it) is brain surgery through a hole at the back of the oil pan.




So that picture above is the new one, but prior to swap.