OM648 E320 CDI Warm Idle Issues
02-13-2019, 10:18 PM
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2006 E320 CDI
OM648 E320 CDI Warm Idle Issues
Hi all,
Brand new to this forum and to modern Mercedes Benz vehicles. I had a 1984 300D turbo, but it was a bucket and I got rid of it a bit ago. I work at an auto broker in Colorado that specializes in enthusiast cars, particularly BMWs, and working on the Benz did not scare me as mechanical work is most of what I do there. I recently decided to pick up an E320 CDI after attending SEMA and getting the wild idea of swapping a modern diesel into a W123 wagon. Google "Honest Assembly SEMA" if you're curious as to why the idea of doing this doesn't intimidate me. While I still would love to do that at one point, I figured I'd probably end up liking the W211 so much that I wouldn't want to dismantle it, particularly when used to driving 80s BMWs, and so I decided to buy a nicer one and not one just good for parts and a running drivetrain. I'd like to think I'm the youngest person to purchase an E320 CDI by several decades (I'm 24). I flew out to Sacramento to pick this one up, and have done about 7500 miles in it since December 2018 (several road trips involved). It hasn't missed a beat, so far I have done:
-Oil change with Mobil1 ESP 0w-30 and MANN filter
-Thermostat (was stuck open)
-Glow plugs (one died so I did the set)
-Blower motor (was squeaking when cold)
-Center dash speaker (was buzzy with vocals, particularly Jimi Hendrix)
-Winter tires (this thing is great in the snow for RWD with the right tires)
Prior to when I bought it:
-Engine was replaced at ~203,500 miles (I bought it at ~207,900 miles). Looking through the records the seller gave me, the best I could figure is the engine had "black death" so bad, and the dealer he took it to was so incompetent, that they broke injectors and messed up the head trying to get them out, the car was at the shop for ~3 months (during which time he bought another E class, hence why he sold it) and he basically said they need to give it back to him ASAP, so the quickest course of action was to replace the motor. I don't know the age or history of the motor, but it uses no oil, doesn't leak anything, and has no surface rust or corrosion anywhere.
-Engine mounts were replaced during the engine swap, and they re-sealed the injectors in the new engine after installing it.
-Car idled and drove flawlessly when I got it and for ~6500 miles, save for some excessive smoke due to the thermostat being stuck open.
I've cold started it down to 0 degrees F with no issue other than sometimes a slight cough and puff of smoke before it idles smoothly. Smoke goes away immediately after the engine fires. It's done this since I have had it, and figured this was normal for a diesel in the cold at altitude (mile high). *However,* recently after a trip from Denver to Silverthorne and back, about 190 miles round trip which involves a climb of about another 5,000 feet altitude at 70-80 mph, the car began idling rough when warm, and sounding like it was knocking, as though it was overfueling on a cylinder or not firing right. The RPM needle bounces around a little and the speed varies by probably 100 rpms if you let it sit there. It only does this when at or near operating temp, not when cold. If you slowly rev it up to ~1100 rpm, the noise and problem disappears entirely and the engine is as smooth as it should be. It drives fine, doesn't feel down on power, is not down on MPG, and makes the 17-18 psi of boost that it should. The car is throwing no OBD codes, but I looked at live data on the scanner and noticed that right after I shut the engine off, the rail pressure went from ~5,000 psi to ~300 psi within 3 seconds, and after sitting for a half hour or so, the rail pressure was at ~30 psi.
I was curious:
-Is the rail pressure supposed to bleed down this far, this quickly?
-If not, is there anywhere else it could be escaping to other than a leaking injector, or faulty rail bleed-off valve? No external leaks of anything, anywhere.
-Is there a good way to check if injectors are leaking without removing them? I have no issue with removing them and getting a diesel shop to test them, but if I can save myself the work, I will.
-Does the leak-off test while running the engine tell me anything about which injector is leaking, if any of them are?
I have a compression tester I can use to make sure I didn't smoke a cylinder or anything, but it really doesn't seem like this is the issue, since the problem disappears suddenly at ~1100 rpm.
The only other thing I have noticed is the lights are a bit flickery at idle when it's doing it's rough idle, but I thought that might be more of a side-effect of the problem rather than a cause, since the RPM varies some. The voltage on the scan tool doesn't seem to vary that much, but the flickering is noticeable. I guess I could hook jumpers to a running car with a known good alternator and see if the problem disappears, and if it's just a product of a faulty voltage regulator.
I appreciate any insight in advance. Thanks!
Brand new to this forum and to modern Mercedes Benz vehicles. I had a 1984 300D turbo, but it was a bucket and I got rid of it a bit ago. I work at an auto broker in Colorado that specializes in enthusiast cars, particularly BMWs, and working on the Benz did not scare me as mechanical work is most of what I do there. I recently decided to pick up an E320 CDI after attending SEMA and getting the wild idea of swapping a modern diesel into a W123 wagon. Google "Honest Assembly SEMA" if you're curious as to why the idea of doing this doesn't intimidate me. While I still would love to do that at one point, I figured I'd probably end up liking the W211 so much that I wouldn't want to dismantle it, particularly when used to driving 80s BMWs, and so I decided to buy a nicer one and not one just good for parts and a running drivetrain. I'd like to think I'm the youngest person to purchase an E320 CDI by several decades (I'm 24). I flew out to Sacramento to pick this one up, and have done about 7500 miles in it since December 2018 (several road trips involved). It hasn't missed a beat, so far I have done:
-Oil change with Mobil1 ESP 0w-30 and MANN filter
-Thermostat (was stuck open)
-Glow plugs (one died so I did the set)
-Blower motor (was squeaking when cold)
-Center dash speaker (was buzzy with vocals, particularly Jimi Hendrix)
-Winter tires (this thing is great in the snow for RWD with the right tires)
Prior to when I bought it:
-Engine was replaced at ~203,500 miles (I bought it at ~207,900 miles). Looking through the records the seller gave me, the best I could figure is the engine had "black death" so bad, and the dealer he took it to was so incompetent, that they broke injectors and messed up the head trying to get them out, the car was at the shop for ~3 months (during which time he bought another E class, hence why he sold it) and he basically said they need to give it back to him ASAP, so the quickest course of action was to replace the motor. I don't know the age or history of the motor, but it uses no oil, doesn't leak anything, and has no surface rust or corrosion anywhere.
-Engine mounts were replaced during the engine swap, and they re-sealed the injectors in the new engine after installing it.
-Car idled and drove flawlessly when I got it and for ~6500 miles, save for some excessive smoke due to the thermostat being stuck open.
I've cold started it down to 0 degrees F with no issue other than sometimes a slight cough and puff of smoke before it idles smoothly. Smoke goes away immediately after the engine fires. It's done this since I have had it, and figured this was normal for a diesel in the cold at altitude (mile high). *However,* recently after a trip from Denver to Silverthorne and back, about 190 miles round trip which involves a climb of about another 5,000 feet altitude at 70-80 mph, the car began idling rough when warm, and sounding like it was knocking, as though it was overfueling on a cylinder or not firing right. The RPM needle bounces around a little and the speed varies by probably 100 rpms if you let it sit there. It only does this when at or near operating temp, not when cold. If you slowly rev it up to ~1100 rpm, the noise and problem disappears entirely and the engine is as smooth as it should be. It drives fine, doesn't feel down on power, is not down on MPG, and makes the 17-18 psi of boost that it should. The car is throwing no OBD codes, but I looked at live data on the scanner and noticed that right after I shut the engine off, the rail pressure went from ~5,000 psi to ~300 psi within 3 seconds, and after sitting for a half hour or so, the rail pressure was at ~30 psi.
I was curious:
-Is the rail pressure supposed to bleed down this far, this quickly?
-If not, is there anywhere else it could be escaping to other than a leaking injector, or faulty rail bleed-off valve? No external leaks of anything, anywhere.
-Is there a good way to check if injectors are leaking without removing them? I have no issue with removing them and getting a diesel shop to test them, but if I can save myself the work, I will.
-Does the leak-off test while running the engine tell me anything about which injector is leaking, if any of them are?
I have a compression tester I can use to make sure I didn't smoke a cylinder or anything, but it really doesn't seem like this is the issue, since the problem disappears suddenly at ~1100 rpm.
The only other thing I have noticed is the lights are a bit flickery at idle when it's doing it's rough idle, but I thought that might be more of a side-effect of the problem rather than a cause, since the RPM varies some. The voltage on the scan tool doesn't seem to vary that much, but the flickering is noticeable. I guess I could hook jumpers to a running car with a known good alternator and see if the problem disappears, and if it's just a product of a faulty voltage regulator.
I appreciate any insight in advance. Thanks!
02-17-2019, 11:50 AM
#2
Member
It can be also ur transmission, usually on low rpms it jiggles a bit. On mine 320 cdi its the same. No obd codes is great news. Maybe its a clogged egr. U should open the plastic cap and clean it after u dismantle it.
otherwise change the fuel filter, cheap and important for the upkeep of rail pressure.
otherwise change the fuel filter, cheap and important for the upkeep of rail pressure.
09-21-2020, 03:28 AM
#3
Bumping this as it's the similar symptoms my E220 CDI has developed after sitting idle during the lockdown and installing a ECU (old ECU fried) and a used rail pressure sensor as previous one was faulty and engine went into limp mode quite often.
After the new ECU (used one made virgin and programmed online) and rail sensor car won't go into limp mode but idle is somewhat rough especially for cold start and once engine is warm, the injector noise increases to a quite audible and irritating knock sound.
got a scan done few days ago and found the fuel flow is more than recommended. Injector #4 has a high flow (software indicates not actual bench test).
When the mass air flow sensor socket is removed, the knock noise stops.
Few questions. Car is W211 E220 CDI 2006 pre face lift
1. Has something similar happened to you? what was the remedy
2. Could it be due to the bad coding of injectors of the new ECU ?
3. Thinking of removing all injectors, clean and pressurise them again. Am I asking for trouble?
After the new ECU (used one made virgin and programmed online) and rail sensor car won't go into limp mode but idle is somewhat rough especially for cold start and once engine is warm, the injector noise increases to a quite audible and irritating knock sound.
got a scan done few days ago and found the fuel flow is more than recommended. Injector #4 has a high flow (software indicates not actual bench test).
When the mass air flow sensor socket is removed, the knock noise stops.
Few questions. Car is W211 E220 CDI 2006 pre face lift
1. Has something similar happened to you? what was the remedy
2. Could it be due to the bad coding of injectors of the new ECU ?
3. Thinking of removing all injectors, clean and pressurise them again. Am I asking for trouble?
