bolenator2018

Hello everyone,

Ever since I have had my beautiful E350, I have noticed a very slight vibration whilst idling. The second day I had the car I got a P0302 code indicating that I had a misfire on cyl #2. Of course, I immediately ran an injector cleaner with a tank of gas and replaced the spark plugs.

When re-installing the coils, I swapped cylinders 3 and 2 to see if the code would jump thus pinpointing a coil issue. However, upon restarting, the code came back and it was good old cylinder 2 again. I have since cleared the code and driven about 250 miles without it returning but I can still feel just a slight vibration. My thoughts are fuel injector or maybe the crankshaft positioning sensor/solenoid. I figure I might as well do both, but I am not familiar with where the solenoid is located.

Any help or advice would be much appreciated.

cmriv

injector possibly, have never actually replace an injector on a M272/273 motor but thats not to say it doesn't happen.


if it isn't an injector i'd be leaning on worn exhaust valve seats...... not very common, however there is a DTB stating so if you own a 272/273.

bolenator2018

We'll cross your fingers it isn't the exhaust valve/seats. She only has 91k on the clock and she pulls like a freight train. So I'd be shocked if it wasn't something simple. Honestly this E Class is perfect unless it sits at idle for 5+ min.

I had another P02​​​​​​302 code pop up today while in a drive throygh. Hopefully the problem is solved by replacing the camshaft sensors and magents. I'm also thinking of replacing the crankshaft positioning sensor for good measure despite the fact that it's located near the firewall.
​​​​

rapidoxidation

Only after idling for 5 minutes, you say? When you changed the spark plugs, did the offending cylinder yield wet plugs? I wonder if you have a leaky injector.

Racin_fool

If the issue is still present, I'd suggest finding a shop to do a compression test and a cylinder leak test.

cmriv

she can pull all she want.... i have a 2009 m273 and certainly notice a rough idle at times when in park. A cam solenoid/sensor is not going to throw a misfire code. Those only relate to timing.....

ollo

Worth a try: Replace plug wire on #2

bolenator2018

No wet plug unfortunately. I wish it had so I would at least have a diagnosis.



Does your V8 ever throw codes? Honestly, if it weren’t for the fact that my engine light comes on every so often. I could probably deal with a slightly choppy idle at times. I had read somewhere that M272s are not known for their smooth, balanced idle.



These cars are coil on plug as opposed to waste by spark so no plug wires. I already swapped coils and the problem is still on cylinder 2.







UPDATE: So after replacing my camshaft sensors and magnets, the problem still persists. I hate shot-gunning parts, but I think my next option will be the fuel injectors or like Racin_fool mentioned, maybe a compression test.

cmriv

M272 is balanced, via balance shaft. M273 is not balance per-say because of block design, only has an idler gear....

Mine does not throw any codes and timing is dead on when looking at actual values. It is possible maybe one of your adjusters is failing too.

bolenator2018

Well, that sounds expensive and internal. at 94k on the clock and it being the last model year, I'd hope it was something less terrible. Before I look into that, I am just going to do coils and injectors to say that they are done... I have driven another 500+ miles mostly city and I have left it idling for 10+ minutes at a time to see if the code would come back. Sa far so good although I still feel a little chop when in park and if I am crawling at 2-3mph.

cmriv

What type of gas do you run? Maybe a fuel additive may help some. It staying on cylinder 2 makes me weary. Maybe before purchasing new coils and injectors, swap 2 injectors. and wait for code to come back on if it even does.

bolenator2018

I used a product called CRC Fuel System Clean Up with a full tank of 91. I did some research and their were many who raved that it was a good product so I figured I would give it a whirl. I have since gone through a tank and 1/2 and the P0202 not returned even though I still feel a small vibration at idle. This makes me think that it could possibly be a fuel issue. I might just swap the injectors and see if the light ever returns. Preying that I didn't just buy a time bomb. lol

bolenator2018

I used a product called CRC Fuel System Clean Up with a full tank of 91. I did some research and their were many who raved that it was a good product so I figured I would give it a whirl. I have since gone through a tank and 1/2 and the P0202 not returned even though I still feel a small vibration at idle. This makes me think that it could possibly be a fuel issue. I might just swap the injectors and see if the light ever returns. Preying that I didn't just buy a time bomb. lol

I also want to mention that I bought new Camshaft positioning sensors and magnets that are going in tomorrow. I've been sitting on that for almost two weeks. Maybe that will sort it out.

bolenator2018

UPDATE: So the flashing engine light came back today and the codes that were present were once again P0302 AND P0300 which is brand new. Now I'm thinking that it probably isn't the fuel injector. MAF Possibly?? I have already replaced all the camshaft sensors and magnets and did the plugs. Honestly, I'm really not looking forward to dropping $800 plus on coils and injectors if that isn't the problem.

I did read that the dealer can Hook it up to the STAR diagnostic and run real-time tests. Do you think this would enable them to find the root cause? I might just bite the bullet and take it to them for diagnosis.

bolenator2018

Final update as the problem has been found. Today I had my local indy perform a compression test and cylinder #2 is showing 100 PSI. The others all show around 160. So I'm assuming that the prior owner put 87 in and assumed it would be fine. Honestly, I'm just going to drive it until the damn thing gets worse and they call the warranty company. I am so glad that I went the warranty route when buying the car. Very depressed by the diagnosis but I guess that's life.

The last few tanks I was putting in fuel cleaners/octane boosters and the issue as basically eliminated and I never got a CEL. How bad would it be for me to add an octane booster to every tank? I say that because I want to wait as long as possible to get the warranty company involved because they aren't going to want to pay out since I have only had the car for a month.

F1Fan

87 octane, regular grade gas, should be ok. The engine has a knock sensor and can retard the timing to compensate for the lower grade fuel. You may not get full rated power, but it'll still run with 87. Have you checked the coil pack? Perhaps try swapping it with a different cylinder to see if the misfire still happens. Then I would look at the wiring for #2. See if that can be swapped to the other side.

cmriv

I called it. Compression is down because of exhaust valve seats being worn. I would not be waiting until it gets worse. I would contact warranty company, have paper/diag work ready to hand over and have them pull some strings. You could get a new head or they may have that 1 seat replaced. The longer you wait the more miles you'll collect. You aren't going to pass a smog test either with a cel on, especially in Cali.....

DO NOT RUN 87, GAS DOOR CLEARLY STATES MIN. 91 OCTANE. It's not a injector, coil, spark plug or wiring defect. It's a mechanical internal engine issue, specifically the cylinder head, cylinder 2 exhaust valve seat. Compression test don't lie.

Maybe find rebuilt heads? Hey at least it's on the easy side of the motor!

cmriv

Customer complaints of misfire, rough running and diminished performance on vehicles with 272 or 273 engines. Check Engine Light CEL (MIL) might be on. Compression and or leak down test results show values out of specification.



Unfavorable wear of exhaust valve seats in cylinder heads. Refer to image examples in the attachments


Replace affected cylinder head on engines up to engine numbers as indicated below. For similar conditions with engines outside of the serial number range, thorough investigation must be conducted including bore scoping combustion chamber for evidence of valve seat wear. Otherwise, claims could be rejected if the origin of the problem is not properly determined and not confirmed with evidence.

Engine 273 5.5L produced up to November 2009 – engine number 273.9xx 30 342934

Engine 273 4.6L produced up to August 2009 – engine number 273.9xx 30 328842

Engine 272 3.5L produced up to August 2009 – end engine number 272.9xx 31 322249

Engine 272 3.0L produced up to June 2009 – end engine number 272.9xx 31 267324


THIS IS A MB BULLETIN THAT CAME OUT IN 2014-or should i say it was edited/revised in 2014. may have come out prior to that....

bolenator2018

Awesome information. I may try and see if I can go that route. Thank you!

bolenator2018

Would you happen to have the service bulletin number for that?

bolenator2018

The problem with going to the warranty company right away is that they will say it was a pre-existing condition. I want to wait a few months before making a claim so that they can't try and deny coverage. I'm actually researching an engine swap. The tech at the indy shop said that a valve job on these is a pretty terrible job.

cmriv

If someone is unfamiliar with the product then yeah i could see that. but it's a engine, just like doing valve jobs on any other motor. Waiting is your call. Even if it was pre-existing, if you have an ex-warr, pre-existing conditions are irrelevant. Especially if you have a cel on.

mcleantmw

Just sharing my experience with this issue on my 2003 E500, which at the time last October had about 186000 miles. I was getting some misfiring noticeable at idle. Took to my independent MB repair shop who replaced all 16 spark plugs and wires. Major improvement, but then noticed still some slight misfiring at idle. I then DIY replaced all eight ignition coils which are each held in place with one screw onto the valve covers. Got Bosch units at Advance Auto for $77 each.......MB Dealer list price I recall was about $130 each. Runs smooth as a kitten purring now.