Clogged Cat or ???
Thread Starter
Newbie
Joined: Jun 2017
Posts: 7
Likes: 1
2007 S600
Clogged Cat or ???
I’m driving about down the highway yesterday after picking up my 07 S600 from an indendant shop who rebuilt my transmission (didn’t go well but that’s another post soon to be) and suddenly the CEL came on and and the car lost power. Still very driveable, at first I thought maybe I blew a turbo since low end acceleration was very sluggish. Car runs & idles smooth. I scanned codes and get P0300,P0301,P0302,P0303,P0304,P0305 and P0306. After some searching I originally thought I lost a coil pack but there are no misfires, again the car runs smooth. I’m wondering if a Cat could have been damaged during removal of the transmission? I put my hand over the exhaust tips on both sides and they seem to flow equally but I did notice the drivers side got hot right away and the passenger side exhaust stays cooler.
Any suggestions on how to diagnose a bad cat? No rattles, no odd smells, but also no power and all these codes. Other than the transmission failure the car has been an awesome ride just hitting 93k miles.
Any suggestions on how to diagnose a bad cat? No rattles, no odd smells, but also no power and all these codes. Other than the transmission failure the car has been an awesome ride just hitting 93k miles.
Super Member
Joined: Feb 2007
Posts: 809
Likes: 74
From: Dallas, TX
2008 E63 wagon (1 of 62)
The only way to really check for a bad/clogged catalyst is to use a backpressure tester in the exhaust in place of one of the oxygen sensors and then go drive the car and check the vacuum and pressure readouts. You could also remove the exhaust system to look inside with a borescope, but that can be hard to access as well and the vehicle and exhaust would need to be cold so you dont melt anything. Because you have the M275 v12, it could be a bad coil pack, worn spark plugs, or even a bad coil pack control module (separate from the coils).
One other thing to mention. I have seen a few M275 engines lately (in the past 6 months) that are scratching the cylinder walls causing compression issues. If you are going to do any of this yourself, you might also want to run a compression and/or leakdown test on your engine to make sure everything is sealing properly.
One other thing to mention. I have seen a few M275 engines lately (in the past 6 months) that are scratching the cylinder walls causing compression issues. If you are going to do any of this yourself, you might also want to run a compression and/or leakdown test on your engine to make sure everything is sealing properly.
Last edited by Racin_fool; Jan 20, 2018 at 05:27 PM.
Thread Starter
Newbie
Joined: Jun 2017
Posts: 7
Likes: 1
2007 S600
The only way to really check for a bad/clogged catalyst is to use a backpressure tester in the exhaust in place of one of the oxygen sensors and then go drive the car and check the vacuum and pressure readouts. You could also remove the exhaust system to look inside with a borescope, but that can be hard to access as well and the vehicle and exhaust would need to be cold so you dont melt anything. Because you have the M275 v12, it could be a bad coil pack, worn spark plugs, or even a bad coil pack control module (separate from the coils).
One other thing to mention. I have seen a few M275 engines lately (in the past 6 months) that are scratching the cylinder walls causing compression issues. If you are going to do any of this yourself, you might also want to run a compression and/or leakdown test on your engine to make sure everything is sealing properly.
One other thing to mention. I have seen a few M275 engines lately (in the past 6 months) that are scratching the cylinder walls causing compression issues. If you are going to do any of this yourself, you might also want to run a compression and/or leakdown test on your engine to make sure everything is sealing properly.
Super Member
Joined: Feb 2007
Posts: 809
Likes: 74
From: Dallas, TX
2008 E63 wagon (1 of 62)
bad/damaged/worn piston rings, possible piston damage can cause the scoring that we saw with a bore scope in the cylinders. The 2 owners didn't want to address that issue. As for the coil pack, they are more than just that. Think of them as a complicated ECU controlling spark, spark timing and even sensing engine knock while talking to the Engine control module and the coil pack control module. The coil packs can seem to work fine with the engine cold, but once they warm up they can start arcing or they could develop internal shorts or other electrical issues. I really wish they would have just stuck with a single coil per cylinder type design like they have used on the rest of the engines. It's overly complicated, overly expensive and prone to failure. Unless you have a hard misfire meaning that its always misfiring due to something like a damaged spark plug, then usually turning the car off and then back on will reset things and let the engine run smooth again until the issues pops back up.
Junior Member
Joined: May 2018
Posts: 20
Likes: 0
From: Atlanta
2004 s55, 2003 330ci , 2003 lx470, 92 landcruiser
Loss of power
I have the exact problem like you but I’m in a 55k . My car suddenly died with all cylinder showing misfire and I have one cylinder severely scored .
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