misfires on all cylinders

I am leaning towards a clogged up/blocked catalytic, especially if it's an aftermarket. I have not checked whether it is yet. Or maybe a fuel delivery issue or a bad ECU, no way that all 8 misfire even if the motor has a head gasket or is bad.

You are correct. That if all cylinders are missing then it is something that affects all cylinders. This would be air or fuel.

So I would start with checking fuel pressure and make sure it is okay.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If the fuel pressure is ok then we need to check for exhaust restrictions like you are suspecting. To do this, I would just remove the up stream o2 sensors and see if the throttle responds better. If it does then the converters are backed up.

If it does not then we could still have an issue with the torque converter. Does the engine rev normally in park or neutral? In other words do you only get this misfire or poor throttle response when in gear?

Lastly, do you only have the misfire codes or do you have others?

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Thanks

Once i hit the pedal several times i can get it to rev, still misfiring. That is in park as well, so the misfire throttle is in park or in gear.

How much fuel pressure should there be when off and when running? Also checked battery and is good and alternator charging.

Just to confirm because it is critical, you have the 6.3L? If so, then max PSI is 90 but operating PSI will be lower. However, do you have any codes for fuel pressure too high or low?

No codes other than misfires, have not done a thorough scan but i will. Yes the 6.3.

I think we have an electrical issue. I changed 4 coils, then cleared it, and started it, still misfiring but gave me a misfire for another cylinder. This car has so much wires/amps in the trunk that was left in it, they only removed the speaker box they had in it, must be expensive stuff. I have never seen anything like this before.
Anyways, there is an additional battery in the trunk with all the amps and wires. Unless I am mistaken this battery has nothing to do with the car itself. So I disconnected the negative battery just in case it has an effect.

Reason I suspect an electrical issue is because the cluster and lights and the whole car just goes off on its own, even before disconnecting the rear battery. While I am scanning it it does that. Once I turn the ignition off and then remove it and reinsert it it comes back to life, and there is flickering a lot...I measured the battery which is not an AGM under the hood and its 12.20...while running around 14....very strange..I will send you pictures, and videos

Attached.

measured the rear battery and it's 10.95, am trickle charging it. I also realized this is the second battery as well which runs the electronics so it must be connected.

Just to take a step back. I should have asked for a video before because that is not just a misfire. When you are revving the engine it sounds like it is knocking pretty bad. It could be just dead cylinders but have you checked compression on this engine?

https://www.2carpros.com/articles/how-to-test-engine-compression

Either way, it sounds like this has some serious issues so before we dig further into the other issues, I would suggest confirming the base engine is okay.

misfires on these engines always sound like a knock, I have owned several Benz v8s, but once you rev it high enough to be solid there is none of that. but these cars are so sensitive to voltage I know that, also the misfire went away on most except 5 for now, am waiting on the battery to be fully charged before I start it again. No I have not measured the compression yet, I cannot even turn it on without starting it enough to measure a compression cause of the electrical issue.

a lot of that is also a backfire from cylinders that are not igniting right.

Where is the fuel pump fuse on this car? I also found while diffing a code p0336 for crank position sensor. Where is it on this engine so i can see if there are any broken wires?

Lights stopped flickering since i charged the rear battery.

Also, after i turn it over and starts for few second i try my best to keep it running but there is barely any throttle response. After it shuts off am hearing a hissing sound from bank 2. Regardless of how good the motor is why would i not get any throttle response.

Also i hear hissing after i turn it off on bank 2.

Let's monitor the cooling system pressure or put 15 PSI to it because that would be the only thing that would pressure bleed noise only after the engine was running. Does it stop or appear to slow down and stop? Does it stop if you turn the ignition on or start the engine again?

https://www.2carpros.com/articles/radiator-pressure-test

As for the throttle input that is most likely due to the ECM shutting it down due to this extremely poor running. Basically it doesn't want you to damage the engine so it shuts that down.

I want to do a compression test on 2 cylinders on bank 2, do you know where the fuel relay is? Or fuse? I will remove two spark plugs and measure both cylinders or 4, i don't need to remove all do i? And dry i guess. Also, keep the gas to the floor when doing that? And what is the range if PSI i should look for?

Pictures of some of the plugs, and the top of cylinders. Can't find the fuel relay to remove and do a compression test.

It may just be the flash but some look okay. However, others appear to be very carbon fouled. That means there is too much fuel going through the engine. Either due to misfire or leaking injectors. Based on this we need to check the fuel pressure and see how long it holds after the key is shut off. Basically how long does it take to bleed down.

Also, to do the compression test, you are going to have to use the relay control module in the trunk because you don't have a traditional relay. If you just unplug this module then the pump won't run. Or you can do the clear flood method as you stated where you hold the pedal to the floor and crank the engine but this is best with two people. I attached the process from the manual to do this test.

Plus here is a guide that will help as well:

https://www.2carpros.com/articles/how-to-test-engine-compression

So turn ignition on so pump can come on then turn ignition off and see how long before the fuel pressure gauge reaches zero?

Thank you. What is the spark plug torque on these?

I don't have that.

Attached below is the torque spec of spark plugs. Thanks

Thanks. Can you find me the location of the fuel pump relay or module? The picture you sent me doesn't match.

Do you know where is the fuel pump relay/ module? The picture you sent me for the truck area looks different than what i have. I have an 08 cl63, if this is all you have just tell me that.

My apologies. You noted that this was a CL and not a CLS but I looked in the heading for the vehicle when pulling that info.

Below is the info for the CL.

It's a cl63, but there is no option to choose it from the menu.

Nothing in the trunk like this, i pulled the back panel and the battery is in there as well as some amplifier connections that were previously installed. battery does not sit in like the picture and there is no fuse or relay box like the picture.

Can you please find it?

Unfortunately we are limited to what the manual says and this is where it shows this for a 2008 CL63 as you can see in the header of the picture.

Is this vehicle in the USA? If not, then that may be the issue. They more then likely put this in a different location for international vehicles and we only have USA manuals.

In the USA, yes.

With new plugs torqued to 22 started much better and without needing to hit the gas pedal. I suspect this noise I am hearing is from a torn/broken manifold gasket. I will need to jack it up to get a better feel.

Runs better with new plugs but still the noise and stalls. Gotten the xentry software and it keeps giving different misfires every time I delete them. But always a knock sensor bank 2.

I noticed the sound around the intake and that the front part was so hot even when the motor wasn't very warm.

I looked through the post and did not see the knock sensor code. So if you have had that the entire time, what is the actual code?

More than likely that is a result of the serious knock that you have but if the sensor is faulty then it is not going to sense the knock and try to adjust for it. However, knock sensors are meant for detonation and not engine knocks like this so even if the sensor is an issue, I doubt that is going to go away.

I suspect that is a spun bearing and if you are feeling heat on the intake then I suspect there is either metal to metal causing heat or valves allowing combustion back into the intake due to them not sealing.

No just recently seen it.

Okay. That code is stored while the others are all current/active. So that means it may have seen an issue but that is not causing this issue.

Just circling back on the compression check, did you ever check compression, at least on the cylinders that are misfiring? Have you drained the oil and checked for metal? Also, have you checked it again since it has been running for coolant again? I know you said it had coolant in the oil when you bought it.

I know we had an issue with the relay but you should be able to do what is called a clear flood and crank the engine and it not start for when you check the compression. This is where you hold the accelerator wide open while you are cranking the engine.

This will cut the injector pulse so that the engine doesn't start. Basically you are telling the PCM that the engine is flooded and you don't want any more fuel so that it doesn't hydrolock.

Clearly try this first just to be sure it works because while I show this in the manual, we have had enough issues with this that I wouldn't want have this be incorrect as well.

Thanks

No not even with the pedal down it will eventually start. I didn't say there was coolant in the oil, there is no mixing and the oil is very clean, coolant is full and clean. Someone suggested the adjusters but am familiar with adjusters noise and it's usually on startups bit the noise is away from the front of the cams. I didn't do any compression tests cause it would still start and am afraid the values won't be correct.

Okay. Here is the process from the manual. It just tells you to remove all the coils and plugs which will clearly prevent the start and vent the cylinders so any fuel will evaporate quickly.