Hello, I am new to the forum. This is my first post and my first MB. I am seeking advice about the best next steps.

==PROBLEM==
I bought a used 2016 E 350 for my wife a couple of years ago. She has put about 45K miles on it and it is currently sitting at about 57K miles (it had about 12K miles when we bought it). We only use premium gas and have the oil changed about every 4K to 5K miles (mostly distance and highway miles). Until this issue arose, the car had been running great and we have been happy with it. We had a B service and a state inspection completed by a MB dealership in our area just before Christmas 2020, so I am surprised that we have a check engine light on now (yellow and steady on, not flashing). I took it out for a test drive and noticed the car hesitates when releasing the break and slightly pressing on the gas just as you would when you start moving after a complete stop (it almost feels like a bumping action as if you were tapping the brake quickly). This bumping subsides once you get going and actually feels fine above 10 MPH. Since the light was not flashing, I took to the highway. There was another noticeable issue of lag or hesitation above 65 MPH and on inclines when more power was needed. Although there was no backfire, I didn't want to push it too hard and so I eased up and gently headed back home. The car has been parked for now.


==TROUBLESHOOTING STEPS PERFORMED AND INFORMATION GATHERED==
When I hooked up my diagnostic device (an Autel Autolink AL539 on which the software is up to date) the port did not respond and seemed dead. I checked the fuse panel and found that the 5 amp fuse to the diagnostic connector was blown (the fuse panel sheet was not where the owners manual said it should be and it was hard as heck to find one online), again surprised since we just had it serviced and inspected at the dealership not long ago. After replacing the fuse, I was able to move ahead and perform the basic OBD2 (Check Engine) test which pulled the following two codes:

1. P0352
   • $7E8 Generic
   • Ignition Coil B - Primary/Secondary Circuit
   • DTC Guide Information (from the Autel device): Open or short in the Ignition Coil. Primary/Secondary circuit. Poor or contaminated connection at the Ignition Coil. Faulty Ignition Coil Primary/Secondary. Faulty Engine Control Module (ECM)
2. P0302
   • $7E8 Generic
   • Cylinder 2 Misfire Detected
   • DTC Guide Information (from the Autel device): Faulty ignition coils. Open or short in ignition coil circuit. Poor or contaminated connection at ignition coil. Clogged or faulty fuel injectors. Open or short in fuel injectors circuit. Poor or contaminated connection at fuel injectors. Faulty or improper spark plugs. Insufficient compression in cylinder. Incorrect fuel pressure. Intake air leak after Mass Air Flow (MAF) sensor.

Since we just had it inspected (which has to pass the gas cap vacuum test), I performed a simple visual inspection of the gas cap and it seems fine (I don't have a way to measure this on my own). I will probably wind up buying a new cap to cover all bases.

==ADVICE NEEDED==
We are just out of warranty from the company we purchased from. Based on the codes and information, I am planning to change the gas cap, spark plugs, and ignition coils. I usually keep my vehicles well into the 250K to 300K range, and 60K miles seems too low to me to be changing ignition coils and plugs.

1. Does this make sense, am I on the right track here?
2. Should I be checking other items (vacuum lines, other fuses, etc...)?
3. Any other advice or tips?

I am not a mechanic, but I have serviced my own vehicles for years and will probably change these items myself. Please let me know if there is any good reason not to do so or if there is anything super special about this car or MB in general.

Thanks in advance for taking the time to read this and for any advice you can provide.

 

I think you'd need to perform more diagnosing if you want to be sure new coils and plugs will fix it. You can swap coils around an see if the misfire follows or not...

 

Actually 60,000 miles is the specified service interval for the plugs on the 2016 E350. So you'll need to do that and might as well do that while you're solving this issue.

I don't think the gas cap is your issue, so I'd leave that be. This scan is too generic and just spewing a bunch of possibilities. Swap the coil from cylinder 2 to another cylinder, clear the codes, drive the car and see if the misfire moves as suggested above. Then replace that faulty coil.

If you're planning to keep the car for a long time, have you considered a more Benz-specific code scanner? We have an MB Carsoft II and it's pretty good at a reasonable price.

 

Thanks, will do. Sounds like I am on the right track. Appreciate the reply.

 

We plan to keep the car for a while, so thanks for those extra details and tip about the scanner!

Would anyone suggest changing all of the coils or just find the bad one and replace it? I'm inclined to change them all. If so, any brand recommendations or specs to consider regarding the coils?

 

Use MB parts. MB of Naperville (google) has reasonable prices. My local dealer was 50% higher priced, idiots.

I would change all the coils. I plan to do this at 100k miles or so. I just changed the plugs recently and have no issues so I didn't change any coils at 50k miles.

 

I usually go with RockAuto for my GM vehicles, but I'll be ordering the MB plugs and coils from Naperville. Thanks!

 

Give FCPEuro a chance.. lifetime warranty.

 

When I changed my spark plugs recently, I ended up with a P0302 I just couldn't figure out.Engine ran perfectly as far as I could tell. Replaced coil, no help.I could clear the code, but it would return immediately upon restart. I took the car to an indy shop who used their scanner and cleared the code, and it has not returned. The problem could be the scan tool, not the car. It was in my case.

 

This is a follow up to my original post.

I ordered a full set of coils and plugs and completed the job this weekend. After a good engine compartment cleaning, I pulled and numbered each ignition coil and spark plug. One plug was obviously different than the others, dark looking and almost black while the rest were a sandy/tan color. I kept everything and may take pictures to post if there is any interest. After getting everything back together, I took the car out for a drive. It was immediately obvious that performance had greatly improved, so I pushed it a little further on some good inclines and open road stretches. Everything felt great and sounded good, but the light was still on (I hadn't cleared the codes yet). When I got home, I connected my scanner (Autel AutoLink AL539B) back up which still produced the codes. Sunnyslope48 mentioned not being able to clear their codes, so I am including what I did here. The following steps cleared the codes:

1. I cleared the codes using the scanner menu selection then exited the program
2. Turned off and unplugged the scanner from the OBD2 port
3. Turned off the car for about one minute (I saw this step in a video)
4. Turned the ignition back to the ON position, but not the engine
5. Plugged the scanner back in (this step turns my scanner on)
6. Ran the diagnostic tests again which revealed that the codes had cleared
7. Ran the I/M ready test which passed in all areas and gave a green check mark, which indicates the car would pass state emissions inspection

This YT video is extremely detailed on the process and helped me immensely .

Thanks again to everyone for taking the time to share your comments and offer advice.

 

I don't have a E350, but I appreciate a person that does a follow up on a solution. It helps the community.

 

Sunnyslope48, please see my 4/26/2021 update. I should have also mentioned that, after fixing the issue, I drove the car for approximately 60 miles (or thereabouts) before trying to reset the codes. Based on what I have read, this gives your cars computer time to check the necessary modules. I believe driving is an important step to clearing the codes coupled with the steps (or similar steps) I outlined. Good luck, I hope this helps!

 

That would an emissions or drive-cycle type of code... I suspect a simple misfire code should clear immediately if the problem was corrected. If you disconnect the main battery, than can often require a drive-cycle.

for 8alonzo8 its great you fixed the problem. I'd be curious about the one plug that was different (black) compared to the normal "tan" ones. Is that the cylinder was misfiring? I'd also think, what caused just the one plug to be fouled and did I really fix the problem.

 

Thank you bmwpowere36m, I agree with you on all points. The code I had was persistent (actually listed as "Permanent" in my scanner) as well until I completed the steps, which could have been a complete coincidence, but I thought I'd offer what I did since mine cleared using those steps.

As to the one coil and plug that was different, I failed to find which one is actually "cylinder 2", but I made a numbered drawing of the sequence before starting and can identify that it was the second one back on the passenger side when standing in front of the car facing the engine (second position, so maybe cylinder 2??). I too am curious about what really caused the problem in the first place, but I really didn't know of a good way to troubleshoot it. I ordered a copy of the WIS (don't know how to use that yet) that arrived after I completed the job. Hopefully, I can use information contained in the WIS to do a complete check of the issue. In any case, I will be checking that specific plug and coil from time to time against the others to see if the problem pops back up, which would indicate I simply put a Band-Aid over the original problem.

 

Based on the WIS, cylinder 2 is the location of the spark plug that was fouled as black. It's not exactly clear to me yet how to use the WIS to diagnose my particular issue (which may not be the purpose of that tool) but I report back if/when I find an answer.

 

Thanks for your writeup. I did exactly same as you several times over several days, the exception being #7. I don''t have a tool that will do that. However, the car was driven probably 200 miles altogether - just couldn't the code to stay cleared.