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Discussion Starter · #1 ·
Hey everyone, Daniel here...

I come with another problem (unfortunately) and hope to find some answers around. Long story short... I was driving, chill, ac on and when I came to a stop the engine started mumbling like it was about to stall. I thought it was from our jerky transmission but it didnt seem to be it (thank God). Anyway, after driving it back home I realized that it does this 'stalling' only on low RPMs. Had the car diagnosed and got some errors, P0300 and P0303 (attached some goodies). Replaced the spark plugs, the ignition coil on cylinder 3 where the error initially was... but no luck afterall.

Now I see this "Turbocharger pressure sensor circuit; signal outside lower limit" and gives me bad days because I dont really get it. As far as I know and as I 'researched' the problem should be from a vacuum leak... maybe the gasoline or the DV.

If anyone knows anything or can throw an opinion on this, it would be very helpful because I'm out of luck and am trying my best to get it done asap... not because "car guy" but because holidays and... car guy :))

The car is a 2014 CLA 250, stage 1+, air filter, pops and bangs, custom exhaust...
PS: I got off the oil cap when the car was running (idle, ofc) and a lot of steam comes out of the engine... I got the DV off to 'clean' it and see if it's gripped or anything but no luck at all....
 

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Did the misfire go away when you replaced plug and coil?
 

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Discussion Starter · #3 ·
Did the misfire go away when you replaced plug and coil?
Yessir. The specific error for the cylinder 3 misfire got deleted and seems like it didn’t came back but still got those random/multiple misfire
 

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Discussion Starter · #4 ·
Just got back from a shop. Need to get down to the engine to see what's damaged. Compression from 14 to 2 on cyl. 3... new piston heads, timing chain... rebuild I guess :) fuck this car and this engine in particular :)
Ps: 140k km
 

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Might be a leaky valve?
Then you can leave the bottom end alone
Hoping for the best
 

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Discussion Starter · #7 ·
Dont know if people following this but I'll let you know what's the deal here.

So, the problem is that a piston (cyl3 one) broke :))
The car has 150k KM, it's a simple stage 1 with pops and bangs and pretty much thats it. The mechanic told me that the pops and bangs or the petrol used wasnt the problem... but the piston was over its limit. How? I dont freaking know because I didnt ever pushed the limits out of this sloppy car. Anything else except this piston is looking good so there isnt any major damages except the obvious. Will still have to 'hoon' the cylinder head, put back four new piston heads, timing chaing and all that...

Couple pictures of what I found inside the engine bay (lucky me? they dropped down on the bay and didnt do any other things in their way down) also with a piece of the tensioner arm (dont ask me how... i already hate this :)) )

If there's anyone curious of anything else please ask me and I'll keep you updated in case you'll have the same problem... Hope not tho!

Cheers,
Daniel
 

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Well could have been worse

The issue with pops&bangs in tunes ... to me at least ... is that does not contribute to power but abnormal conditions in the combustion chamber in order to produce odd acoustics but that energy has to be derived from somewhere (just like backfire in older engines which is not a good sign)

Anyway your piston suffered latent damage from one adverse event which clearly propagated over time leading to full failure
That latent event could have happened as one simple “ping” many miles ago and hit an internal “defect” within that one piston and the rest is history (they are cast)

In fact spark plug ground tab location issues have caused damage too since the flame front propagation is not per design and affects pressure distribution but thats another can of worms

May your motor revival go smoothly and run on for many more miles
 

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Discussion Starter · #9 ·
Yessir could've been way worse. Thanks a lot for the reply! So you're saying that the pops and bangs thing really did something afterall, right? Indeed the other pistons havent got anything on them or any sign of bad detonation or anything like that, also the top of them looks like "new" but I think it doesnt matter afterall. Should I just go remap the ecu without the pops and bangs?

PS: I didnt run the engine like... over its limits or track the car. It's just a daily and I went for the stance look, not the power and all that. Indeed I did couple runs with some friends and here and there I worked it 'hard' but nothing like a track day or anything like that... it's a little odd to me that this happened to an engine that's fairly 'new' I mean I have a 1.8 kompressor from 2004 with 300k km on it and it's running like a mofo since day 1... and that car has seen a lot...
Anyway, can you please explain a little more about the spark plug? I didnt got it very well so maybe its something I should 'change' in the future?

Again, thanks a lot for the reply :)
 

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I learned a fundamental rule back in time ... if it doesnt make it go faster, dont bother

If youre gonna retune do it for power and smoothness with no transients ... think your motor would be happier

I posted an article about plugs ... try a search here ... but one member noticed poor performance with “similar” plugs and resolved it with factory plugs
The issue is where the ground strap is relative to the thread start point and that position consistency among the 4
 

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Discussion Starter · #11 ·
I learned a fundamental rule back in time ... if it doesnt make it go faster, dont bother

If youre gonna retune do it for power and smoothness with no transients ... think your motor would be happier

I posted an article about plugs ... try a search here ... but one member noticed poor performance with “similar” plugs and resolved it with factory plugs
The issue is where the ground strap is relative to the thread start point and that position consistency among the 4
Pff :) Indeed sounds most relevant and that's what I'm going to do after it's done.
Got it about the plugs, yeah, well, mine didnt had anything bad on the part that creates the spark, all was good. The only 'reason' to say so that my mechanic told me is that he thought I ran the car on track too hard... wich again I did not. He simply said that the piston broke because he just couldnt take anything more and was over its limit. Me, honestly I hope that it was a simple 'error' when making it since Mercedes aint what used to be... but whatever. Instead of wrapping it now I have to do the engine :))

Again, thanks for the info! You're amazing!
 

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Discussion Starter · #14 ·
Hey guys... little update and some more help needed: After a month and couple weeks of having the car at the shop... the car engine works and sounds fine buuuut the turbocharger somehow "whistles" wich it didnt before having the engine repaired...

I know our turbocharger comes in one piece with the manifold wich isnt broken as the mechanic said, either the engine block or anything. They and I... think is the bearing inside the turbo.
What I'm asking is... is there anything I should watch or know before sending the turbo to a shop that can check it out? Should that bearing be 'dry' because the car didnt run for a month and a half and can 'recover' after the car will be getting out for couple tests/runs so they can see if the engine/repair is done good? Anything? Please help... I'm getting frustrated and already sick of this piece of crap car :(

Cheers and a beautiful Sunday,
Daniel
 
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