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Discussion Starter · #41 ·
Pressure/smoke tested vac and exhaust and all looks tight! May do another round of seafoam from the PCV nipple. That's a good spot to focus on! I'll have to rig up the right hosing.

My LR Master Tech took a listen and did mention that while it sounded good, the rumble I'm picking up on is more common with the 4.6 block since it's way higher compression/performance driven.

Back to the rich running, misfiring cause: The best diagram I can find quickly is this one:

Motor vehicle Automotive tire Font Automotive exterior Auto part

My vacuum isn't holding, and I knew this. I simply didn't understand WHY this was important. It's not like a vacuum advance, but is critical to flow of fuel.

My diaphragm is not holding vacuum, so it does not allow for fuel return . So all the pressure will go to the rail and the only way out is through the injectors. There is no monitioring of fuel pressure in the rail, so everything relies on the regulator operating correctly.

As I mentioned earlier, no matter which injector I disable by pulling the harness off, it will fuel BETTER on the even side. Disabling one injector helps... but obvviously this kills one cylinder. POint is, it's the right rail that's overfueling. Not one injector.

The layout of the rail is biased to the right side, because that's where the fuel comes in. Pressure is being relieved out of the first available exit point.

There's only one way to tell if this is the source (or one source) of the issue. I've got on on order and will swap Tue and post results.

Thanks!
 

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Wondering if you purged the fuel trim value memory storage by disconnecting the ECU from the loom to remove legacy values after the spark plug change ?
With a fundamental difference in combustion it should start again from baseline program to give clear assessment of current status.
 

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Discussion Starter · #43 ·
I just reset the ECM after installing the new Fuel Pressure Regulator.

Feels like for the first 1/8 tank it's dialing in the new operating standard. BTW, the regulator is a pain to swap in situ... but probably easier than pulling the fuel rail. The bolts are super tricky to get to and catch when they come out. I did manage to get them out, and the old FPR out. The new one went in, but lost the bottom bolt somewhere in the back of the engine bay. Heard it roll out when I drove around the first corner. Fortunately it's just a nut that got lost, easy find at the hardware store. One can hold it in place for a few days easy. It's tight.

New operating sounds like it's purring way more, sounds better, just all around. I know it takes at least a 1/4 tank to get some fuel trims going, so waiting to see where we are after a long drive today. But, 20 miles on it already in town and tank is basically still full. That's a better sign, as last tank only took me 79 miles. Yeah, that bad.

more after a drive today.
 

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Discussion Starter · #44 ·
New Notes: After my technician said it checked out, I decided to do the seafoam into the pcv valve, per @Bill B. I'll just leave this right here:


So, I put a new gasket here last month. I did a copper sealant on it too. It's tightened all the way down. Any ideas if there's a trick with the 3 studs that are in the exhaust manifold downpipe? Like, is it possible they don't work, or they're not all the way in, or something easy to miss? Gasket is Atlantic British. I didn't machine this side of the exhaust, but it wasn't bad.

Since it's spewing air OUT, it would seem that the O2 might be reading that it's short on oxygen, so it think's it's rich... then tries to cut fuel? My LTTrims are like -70 on this side. Not sure I follow the O2/ECU logic here and how a leak before the O2 would cause it to read rich.
 

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New Notes: After my technician said it checked out, I decided to do the seafoam into the pcv valve, per @Bill B. I'll just leave this right here:


So, I put a new gasket here last month. I did a copper sealant on it too. It's tightened all the way down. Any ideas if there's a trick with the 3 studs that are in the exhaust manifold downpipe? Like, is it possible they don't work, or they're not all the way in, or something easy to miss? Gasket is Atlantic British. I didn't machine this side of the exhaust, but it wasn't bad.

Since it's spewing air OUT, it would seem that the O2 might be reading that it's short on oxygen, so it think's it's rich... then tries to cut fuel? My LTTrims are like -70 on this side. Not sure I follow the O2/ECU logic here and how a leak before the O2 would cause it to read rich.
Good job Adam on persevering and finding that. That leak will throw off the O2 sensor readings by a lot and so your trim levels will be horrible.
I had the same issue of sealing the Y pipe to the exhaust manifolds after replacing the Y pipe for a non LR one. My cats were blocked so I went most affordable route. The original Y pipe flanges, and the pipes are heavy duty and so warpage of the flanges is not much of an issue. My new Y pipe flanges were a bit on the skinny side and I had a hard time getting a seal using the metal gaskets. As I knew I had other issues I wanted to get the obvious out of the way quickly. I found the following composite flange gaskets.
Remflex 33-001 for $25 from Remflex online. These allowed me to seal the gap and stop all pipe to manifold leaks. How long they will last who knows but they worked. If you have the original Y pipes the best way to get a good seal was to do the following.
Unbolt the muffler/exhaust end of the Y pipe and suspend it from the overhead with rope or wire. Loosen then remove all 6 flange nuts and drop the front of the Y pipe clear of the manifold studs. I put the new gaskets over the three studs and used a long cable tie to make sure they didn’t drop off. It can be fiddly to do. I then pushed the front flanges over the studs this trapping the gaskets, remove cable tie, and then put the front nut on Each side. I always found that the front of the flange leaked if I didn’t unbolt the end of the Y pipes. Once you have one nut on each side put the others on and tighten in a cross patten . I made sure the front nut was tightened to torque first then the two side ones. Once both sides are torqued up then reconnect the rear end of the Y pipe to the middle muffler/exhaust box. Once all is tight do some more Seafoam. It will soon show you how tight it is. In my case with the Remflex gaskets torqued to 18ft lbs was enough, per manufacturers spec, and now fuel trim was good. I did put Hylomar blue between the Inlet manifold and the trumpet housing underneath and it did seal better.
Again well done. I have learned one thing about the 14CUX system and that is it does not like vacuum or exhaust leaks before the O2 sensors.
Well done
Bill
 

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Discussion Starter · #46 ·
Bill, GREAT info. This method of installing the downpipes gaskets is fantastic. My left/odd bank exhaust is air tight, so I'm only working on one side (right/even), and I think I could get the thing put together fine, except the studs are gonna be tricky to get out in situ, so I may have to pull the whole manifold and while out may take it over to the machine shop. Not idea, but good long term.

Those Remflex gaskets look ideal, and I may go ahead and get some on the way. The metal ones, I'm surprised, seal at all. It would seem they need a much better surface and system to install, but may last for ages.

I'm SUPER excited to get this part done so I can start checking trims and find my missing gas.
 

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Discussion Starter · #47 ·
addition

I took off the exhaust manifold to fully re-do things. A couple of things I've learned that I may have missed.

1: I had originally machined the cylinder head side only because, as a newb, I didn't know how to take the studs out of the downpipes end. This was an oversight and I really should have done so first pass because....

2: Upon removing the studs, it became clear that the front stud was troublesome for some reason. All others came out Using 2x nuts back to back and unscrewing the stud. But the 3rd one wouldn't allow the nut to unscrew from the stud. Just one nut, like the thread was messed up or something. So, it's very possible that when tightening the gasket in, it simply would not screw down all the way.

3:Once the studs were all removed, it became clear that the actual surface of the downpipe flange was not even. It may be that before I put a new y-pipe on a few months ago, both flanges had warped together... but the new y-pipe and the old manifold were NOT seating pretty. This problem would have been introduced back when my shop put the y-pipe on... and voila.... new issue with the ratio. MAN, you have to keep an eye on these things or you can fix one problem, and make 2 more.

So, new gaskets/studs/nuts on the way and I have a machine shop doing the downpipe surface. !!!

Will be in the yard Sat am working this stuff out and hoping for a smooth process.
 

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Discussion Starter · #48 ·
Second attempt at a gasket not sealed 100%. I had the surfaces machined, and did a near surgical process of setting and tightening. I'm wondering if the orientation of the gasket makes a difference. These AB metal ones have one side with crimping of some sort. I put that side down since the flat gasket surface matched the flat machined manifold surface best. Or, wondering if these need a few runs to cure/expand. But the main exhaust gasket is always air tight. So, like you said Bill, maybe just a problematic mating of 2 metal surfaces. Asking my tech what he uses since he did my left side way back and it's air tight.
 
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