Struggles to start and single bank misfires only when cold?

[Tapps33]

Ok folks, I've been trying to locate this particular gremlin, and I'm hoping someone else has experienced it. It started shortly before I swapped my chains out roughly 25K miles ago...or about 3 years ago. (Yes, I've been trying to sort this for a while)

Here are the symptoms: When it's cold, it'll crank a little longer than normal. Then, when it "high idles" after startup, it idles rough. Then, every now and again I get a "misfire on cyl 2,4,6,8" "random misfires on startup" and "misfire detected on start up first 1000 revolutions". Once the engine is hot, it typically fires right off, only hesitating every so often. I can't seem to find a pattern as to why it only struggles to fire sometimes vs. others.

Now, here's everything I've tried...some of this was preventative in nature, and some of it was me trying to track the issue down.

New chains, tensioners, injectors, coils, cam variators, plugs, gaskets, front and rear crossover tubes, thermostat, pcv valves, smoke check, new cam position sensors, new crank position sensor, new oxygen sensors (all 4 of them), new HPFP, new LPFP, new MAF's, new MAP, new intake VVT solenoids on both banks, removed and resealed the valve covers, removed timing covers and re-checked engine and fuel pump timing, new alternator, new battery, new radiator (probably not related, but thought I'd include it)....I think that's it. (there's other projects, but they're infotainment and driveline related)

Things I know: The coolant temp sensors appear to be reading correctly based on outside air temps and prior to start they all agree. The long term fuel trim on bank 1 is -8.6% and on bank 2 it's -12.5%. This can be seen by the fact that the bank 1 injector pulses are approx .0001s shorter. Aka Bank 1 is .00125s and bank 2 is .00118s at idle. All the other readings appear to be normal...with the potential exception of the throttle body...maybe (explained below).

I've found something online that pretty much says what I have, but you have to pay the site to access it, AND you need an ASE certification to see the "solution"....if there even is one! What a bunch of crap!
The site is here in case anyone belongs and can see what they came up with:

2016 Land rover LR4 misfires on cylinder 4, 5, and 6 (Bank 2) – Diagnostic Network

So this vehicle was brought to us after another shop replaced all timing components, camshaft gears, and both high pressure fuel pumps. Was told vehicle originally had cam, crank correlation faults and noisey timing chain. Timing chain job was performed along with all 4 camshaft gears. Cam crank...

diag.net

I'm almost at the end of what I can fathom it being, but I have a few more ideas I wanted to run by everyone:

1. Cats are a little clogged up, just enough to cause a miss at low rpm, but then flow enough when the throttle is open and the engine is warm. (Gotta admit, I kinda just wanted to swap the cats out for 200 cell cats and re-do the exhaust anyway)

2. Throttle body needs to be re-calibrated. I've cleaned it a few times....and there's a chance I swapped it with my other LR4 when I had it off, honestly I can't remember. That said, I noticed the commanded and actual values, along with another "position" value were different when looking at live data on my GAP tool. ('ll grab values and post them)

3. I haven't replaced the exhaust cam solenoids, may?.....that said, they're always pretty close to each other and seem to schedule the VVT just fine, so I don't really think it's them.

4. Engine PCM - I've heard these can start to go bad. However, I feel like the engine just wouldn't run, or would be really crappy all the time...it wouldn't be intermittent.

I'm also going to borescope and compression check it just to ensure everything looks good internally. No, I don't have a leak down tester on me, and yes, I know that would tell me a lot more.

If none of the above fixes pan out, I'm pretty much out of ideas.

Any thoughts, comments or inputs?

 

[Tapps33]

I went ahead and pulled the live data for the throttle body.

This is before start with the engine on

Here’s the data for “high idle” just after start:

And finally, here’s the info for idle:

It sorta seems to me that the throttle is open more than it’s supposed to be? This causing the struggles start and misfires?

Like I said, I’m kinda grasping at straws here. I know it’s gonna end up being something really stupid…I just haven’t locked it down yet.

 

[jlglr4]

You've covered a lot, pretty tough to come up with any more, but I'll grasp at some straws with you:

I know at least a couple of people on here have reported exhaust manifold leaks - bolts sheared off. I've read that an exhaust manifold leak can cause rich or lean conditions depending on whether it's letting air escape or sucking air in - either way, it can throw off the o2 sensors.

Another thing that comes to mind is the purge valve. If you have a lot of vapor in the canister and the valve isn't working right, it can cause a rich condition.

Finally - coolant temp sensors. If they're giving a false reading to the ECU, you won't have the correct fuel mixture - particularly at a cold startup when the car is not in closed loop feedback.

 

[mav100]

Ok folks, I've been trying to locate this particular gremlin, and I'm hoping someone else has experienced it. It started shortly before I swapped my chains out roughly 25K miles ago...or about 3 years ago. (Yes, I've been trying to sort this for a while)

Here are the symptoms: When it's cold, it'll crank a little longer than normal. Then, when it "high idles" after startup, it idles rough. Then, every now and again I get a "misfire on cyl 2,4,6,8" "random misfires on startup" and "misfire detected on start up first 1000 revolutions". Once the engine is hot, it typically fires right off, only hesitating every so often. I can't seem to find a pattern as to why it only struggles to fire sometimes vs. others.

Now, here's everything I've tried...some of this was preventative in nature, and some of it was me trying to track the issue down.

New chains, tensioners, injectors, coils, cam variators, plugs, gaskets, front and rear crossover tubes, thermostat, pcv valves, smoke check, new cam position sensors, new crank position sensor, new oxygen sensors (all 4 of them), new HPFP, new LPFP, new MAF's, new MAP, new intake VVT solenoids on both banks, removed and resealed the valve covers, removed timing covers and re-checked engine and fuel pump timing, new alternator, new battery, new radiator (probably not related, but thought I'd include it)....I think that's it. (there's other projects, but they're infotainment and driveline related)

Things I know: The coolant temp sensors appear to be reading correctly based on outside air temps and prior to start they all agree. The long term fuel trim on bank 1 is -8.6% and on bank 2 it's -12.5%. This can be seen by the fact that the bank 1 injector pulses are approx .0001s shorter. Aka Bank 1 is .00125s and bank 2 is .00118s at idle. All the other readings appear to be normal...with the potential exception of the throttle body...maybe (explained below).

I've found something online that pretty much says what I have, but you have to pay the site to access it, AND you need an ASE certification to see the "solution"....if there even is one! What a bunch of crap!
The site is here in case anyone belongs and can see what they came up with:

2016 Land rover LR4 misfires on cylinder 4, 5, and 6 (Bank 2) – Diagnostic Network

So this vehicle was brought to us after another shop replaced all timing components, camshaft gears, and both high pressure fuel pumps. Was told vehicle originally had cam, crank correlation faults and noisey timing chain. Timing chain job was performed along with all 4 camshaft gears. Cam crank...

diag.net

I'm almost at the end of what I can fathom it being, but I have a few more ideas I wanted to run by everyone:

1. Cats are a little clogged up, just enough to cause a miss at low rpm, but then flow enough when the throttle is open and the engine is warm. (Gotta admit, I kinda just wanted to swap the cats out for 200 cell cats and re-do the exhaust anyway)

2. Throttle body needs to be re-calibrated. I've cleaned it a few times....and there's a chance I swapped it with my other LR4 when I had it off, honestly I can't remember. That said, I noticed the commanded and actual values, along with another "position" value were different when looking at live data on my GAP tool. ('ll grab values and post them)

3. I haven't replaced the exhaust cam solenoids, may?.....that said, they're always pretty close to each other and seem to schedule the VVT just fine, so I don't really think it's them.

4. Engine PCM - I've heard these can start to go bad. However, I feel like the engine just wouldn't run, or would be really crappy all the time...it wouldn't be intermittent.

I'm also going to borescope and compression check it just to ensure everything looks good internally. No, I don't have a leak down tester on me, and yes, I know that would tell me a lot more.

If none of the above fixes pan out, I'm pretty much out of ideas.

Any thoughts, comments or inputs?

Seems like it might be a head gasket issue and a combustion in the coolant test or leak down tester would be where I would recommend starting.

 

[powershift]

I'd remove the cats and see if the problem reproduces. If it isn't back-pressure related my guess is it isn't getting enough fuel. When it gets warm things expand and the problem may not reproduce after that.