Stuttgarten

I've owned this car for about 3 months now. I've had a situation where after starting on a warm engine, it immediately dies out. It will restart, but a little shaky like there's an electric short or gas/air mixture problem, not sure! It has happened 3 times thus far. I've also noticed that when restarting on a warm engine, it starts kinda harsh, like one is putting their foot on gas. We're over 113K miles now, and it's a PZEV vehicle. All services were done at dealer. On PZEV cars, many systems are under warranty until 150K miles.

I've recently ran a star diagnostics on it but nothing came up. Not sure if taking it to stealer is worthwhile since they'll charge me for diagnostics and end up telling me all is fine.

KEY08

Yeah, the dealer will most likely have no answer since it is not throwing any codes. Your battery is showing a strong state-of-charge as well I assume?

thefisch

I recall stories of warm start issues due to a bad crank position sensor. Might want to search on that.

KEY08

I had a bad CPS in my W211 E500, but it threw a code. My CPS issue was a car that had a long crank before firing. And sometimes did not fire at all.

Stuttgarten

Yes, battery is charging fine and when doing diagnostics, it shows 14.8V. No codes for current symptoms! It cranks up from first touch and fires up every single time. On cold engine, it start nice and smooth. If CPS is the culprit, is it a matter of time till it throws a code?

KEY08

Stuttgarten

FCP Euro has CPS for $50! Looked all over for a DIY PDF, but none could be found for M276 engine.

konigstiger

WIS...

Stuttgarten

Konigstiger, as always, you came through! Very much appreciated!

Cosbyva

Hi Stuttgarten,

Ive got the exact same issue with my 2013 E350. Intermittently starts then dies just like you described. No CEL. After a few tries will start with rough idle til you give it a little gas. Wondering if you have been able to fix and if so was it the CPS?

thanks!

pierrejoliat

Mine never had a CEL, I would start it and it ran fine until it warmed up, then it would die. I would let it cool down, then it would start fine, until it warmed up again. I had the CPS replaced and it was fine after that. It did progressively get worse over the course of the five days when it started stalling until I had it changed out.I had this issue in two previous Benz's.

Stuttgarten

Unfortunately, the problem occurs intermittently and I never resolved it. I've repeatedly scanned the car, and never did it show there was a problem. So, I just live with it. It's been like a couple of months and it hasn't done it.

Cosbyva

pierrejoliat and Stuttgarten,

thanks for the feedback.

Stuttgarten, did you try changing the CPS?

thanks!!

Stuttgarten

I never changed CPS because I prefer not to throw parts at car without having a diagnosis. My diagnostics showed no codes or problems. Also, the problem is so random and occurs when car is cold and also when hot, and it could occur 2 days in a row or be problem free for 2 months, as was the case recently. I decided to change spark plugs recently hoping it would change the situation, but it did not help. I'm at a loss, and seriously thinking of ditching this W212 and owning no more Benzes. I'm an avid reader of Consumer Reports and Mercedes almost always gets poor reliability marks on that reputable publication.

nota_amg

That's funny, since you just threw spark plugs at it...CPC is WAY cheaper than spark plugs...SMH

Mud

Whenever I'm faced with random fail/ok scenario I will usually look at wiring and connectors first.

Of course there's no hard and fast rules on repairs but sensors "typically" will store a code as they fail. May not activate CEL but sometimes a permanent or pending fault can be found when looking at vehicle modules and not necessarily in generic OBD data.

Suggest a close visual and hands on wiggle test of engine wiring and connectors and upstream O2 harnesses/connectors. If there's a problem there, it can show up as that random problem you've described.

This can be maddening. Couple years ago I went crazy trying to find random misfire on son's civic. Finally traced it to 2 poor pin connections at the ECU. I don't drink but I seriously considered it at that time.

nota_amg

I've seen more CTC fails on Mercedes without codes. In fact, that number is way higher than the number WITH codes. Just my personal experience.

Stuttgarten

Car had reached 120K miles, that's when plugs need changing. Still funny?

cetialpha5

Sometimes the diagnoses is more than the parts. In this case, the parts are cheap enough that you mind as well throw some parts at it. You normally avoid throwing expensive parts at a problem, no issue with throwing cheap parts. Every car brand has its quirks. This is probably one of those MB ones, I already have a spare, bought it as a filler to get free shipping at one point. Won't be surprised if it fails at some point, just like motor mounts, almost like a standard maintenance item.