Mercedes-Benz GLA Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
12 Posts
Discussion Starter · #1 ·
First off, which cylinder is cylinder 1? I can’t for the life of me find the answer.

Got ready to leave for a car and music festival (Gridlife) and my car started acting funny. Got gas, turned it back on and it finally threw a code: Cylinder 1 misfire.
I erased the code, replaced all spark plugs, started the car and it seemed to be idling and running just fine. I took it for a cruise and as soon as I got into boost, it started breaking up really bad (worse than before) and started sounding like a Subaru.

Car only has 18k miles on it, but it’s not stock and I’ve been running my newly tuned and built set up for about 5k miles.

My next guess is that my coil pack failed… but in order to chase that, I want to swap them around and I need to know which cylinders are which.

Thanks for any input or help!

Shane
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #3 ·
Hey. Probably it is caused by faulty spark plug or bad fuel octane.

Changed all the plugs, no change.

Moved coil packs around, no change.

Move other ignition stuff around, no change.

Compression test showed: Cylinder 1: 150psi, Cylinder 2: 147psi, Cylinder 3: 147psi, Cylinder 4: 150psi
 

·
Super Moderator
Joined
·
851 Posts
Please lets us know what year and model. Make it easier in any future posts. Go to the top right of the screen click on the D then click on "My Profile", then click on "About", then scroll down to Signature and put in the year and model of your GLA.


This info can help in trying to answer any questions.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #5 ·
Please lets us know what year and model. Make it easier in any future posts. Go to the top right of the screen click on the D then click on "My Profile", then click on "About", then scroll down to Signature and put in the year and model of your GLA.


This info can help in trying to answer any questions.
Done.
 
  • Like
Reactions: gbarringer

·
Registered
Joined
·
12 Posts
Discussion Starter · #7 ·
Try to move the injectors around. But have o-rings for them ready.
Aren't these injectors really tricky to remove though? Special tool required? The fuel rail looks relatively easy to get to. I'm waiting to install a new sensor in my wideband, since mine doesn't work and to see what my AFR's are at idle and under load.

I was also thinking maybe Crankshaft Position Sensor? It seems that is a common failure on these cars that can cause a random assortment of problems AND doesn't always throw a code.
 

·
Registered
Joined
·
136 Posts
I am thinking about your statement regarding the crankshaft position sensor not throwing a code.
If I was to make such a statement, I would feel a need to analyze the situation.
I would have to break open the Xentry kit, and find a complete list of codes for this car.
Now, you do realize that there are two "levels" of interaction between a testing rig and a car. There is the OBD2 level, using a pep-boys style scanner and then the Factory level.
A pep boys scanner can't even get on the car's Car-Area-Network (CAN) and only scans the ECU, not the TCU, not the other nodes of the network.
So, it should come as no surprise that the more or less SAE mandated OBD2 codes are not comprehensive and that the XENTRY can do a lot more.

In sum:
Looks like you're a technically inclined guy, looks like you're facing some problems with your car, get yourself the tool that you need to address this, a Xentry rig. The Xentry will also have installed the Factory Service Manual, which will answer your question regarding special tools needed to extract the injectors.
As a bonus, it will also have installed the parts software, which will allow you to know the part number of a part you need to replace. I found in the past that googling a part that you need to buy by the part number, has a habit of sometimes producing unexpetedly low prices, as some people have the part for sale, but have no clue what it is and what it does, just have an overstock from ... somewhere.
I will look up the injectors for you, when I get to this.
 

·
Registered
Joined
·
136 Posts
About wideband and AFR.
I totally understand your statement, I come here from a 15+ year interaction with a Subaru from the early 2000's, a narrowband, open loop car.
I suspect that these cars are wideband, closed-loop cars.
I know for a fact that my 2010 C63 is one, it's only open loop moment is during decel.
I've been too lazy to confirm that the GLA45 is closed loop, wideband, for s tupid reason:
The Europeans don't like to measure in AFR, they like to measure in Lambda.
As i was staring at live data in the Xentry for the 45, yes, I had the lambda in front of me, but didn't want to break open the phoen Ap and see what those numbers meant, to confirm wide-band values.
I felt that I know enough about what Mercedes was already doing in 2010, to conclude that in 2019, there's no way that they were't closed loop all the way (therefore wideband).
I still think that I'm right and that with a Xentry, you won't need to drill the factory exhaust and install an unreliable (but accurate) oxygen sensor, that you then have to replace every 9-10 months, to know what your AFRs are all the time.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #10 ·
I appreciate any legwork you put in for me. The Xentry thing sounds pretty sweet, just not sure how I'd go about getting it done? It looks to be an overseas company and I'm here in the US. Not to mention my car is modified and tuned, so I wouldn't want anything to jeopardize or erase my tune. I'm sure they could work around that though... and the very least, the extra or more thorough diagnostics would be great. It might shed a little more light as to what is going on.

As far as the wideband. There is a factory wideband installed on these cars. I have an aftermarket one (as well as a boost gauge) already installed. My sensor is bad currently, but I do have a replacement on hand.

Shane
 

·
Registered
Joined
·
1 Posts
Hey there, did you ever get this issue sorted out? I have a CLA45 AMG, also modified to stage 3 and tuned. Been getting a misfire when coming into boost around 4k RPM and is intermittent to redline, but worse as boost initially comes on. Sometimes it'll break up bad, other times barely. Replaced all plugs, didn't fix it. Replacing coils now...

My car is not throwing CEL for misfire, but I do have a CEL for my downstream O2 sensor. Ordered a replacement bc Rock Auto had the exact OE Bosch for $50 shipped, but I doubt the downstream O2 would cause a miss this bad??
 
1 - 11 of 11 Posts
Top