Hello Everyone,

So just to make a long story short. I drove my car on comfort and the check engine light went on. I went to my mechanic and ran the OBD Handheld and it stated knock limit has exceeded on multiple cylinders. Now this is the second time this has happened to me and I had my mechanic reset the Check Engine Light. It happened twice in my car's lifetime and they were about 3-4 months apart from each other when the check engine light went on for the knock limit exceeding. My car currently has stage 1 DME tune and Catless downpipes. I contacted DME and they told me this issue isn't common with C63's with the same tune.

I just recently replaced the spark plugs to NGK's.

I was talking to my mechanic, DME, and some of my friends about this whole situation and we are all almost positive it's because I let the car go pass a 1/4 of a tank of gas. The check engine light did come on when my car was 1 bar left of gas in the dash.




Can anyone chime in to help solve this issue?

 

1/4 tank of gas-----what planet are you from---return the car to stock or sell the car

 

Uhm, agree - I run my gas tank to empty every week....never fill up until its like less than 50 miles left.

 

+1 for me

 

You've been very knowledgeable in this forum and in our cars in general. Do you think that's why I had those knock limit codes?

 

the context from OP was that he thought it was happening because he let his tank get near 1/4 empty.

if you had bag gas or incurred bad gas , that would cause the knock etc. but i have run my tank down to it slurping for every oz.

no issues.

i as well dont fill my car up until its near empty (50 miles etc) more so out of laziness ..

 

Are you tuned? I'm thinking since i'm tuned, the needs to not run below a 1/4 of gas. Also I'm not sure if the "what world are you from" guy was being sarcastic or serious. If you guys don't think its the gas thing, I'm not sure at all what's making my car throw the knock codes every 3-4 months.

 

I am tuned with stage 2 and no issues running gas tank empty. Do it all the time.

 

I'm guessing this knock limit exceeding isn't a common problem on here. I've only found it in the W204 Sections and they weren't on AMG's.

I just can't figure out what would cause this because I only put Chevron, Mobil, or Shell in my car (Premium 91). I asked if my car was tuned for Cali 91 gas and DME said it was.

 

Looking at your logs, one states "knock control is faulty". Perhaps that's what is causing the individual cylinder knock limits. Another words, its a side effect rather than the cause?

 

I guess I have some knock sensors to replace. Hopefully it doesn't cost an arm and a leg.

 

stage 2 Renntech , AWE Switchpath exhaust, modalworks intakes

 

I guess "knock on wood" comes to mind..

 

 

The guy was doing WOT pulls with 1 bar of fuel in the tank and got multiple cylinder knock threshold exceeded for the second time during this exact same scenario, I wouldn't imagine it's too far fetched that this is indeed a contributing factor (I know this info from another AMG group). It's also not too outlandish for the tuner to suggest not running below 1/4 tank if you're out there bagging on the car. Whether that's actually the cause, who knows, but it doesn't take a brain surgeon to know that having no fuel in the tank and beating on the car is the perfect recipe for starving the pump and going lean IMO, especially on a car that is tuned requiring more of said fuel. Hopefully that's all it is 🤷‍♂️

 

I just reread the original post and nowhere did it say it happend while doing WOT pulls but instead he says he was driving in comfort mode? Where do you read that he did WOT pulls? If so, that would make some more sense even if not entirely clear.

 

What thread you reading ??? never heard of the OP doing WOT pulls ??

 

He's in a group chat that I'm in for amg's on Instagram so I knew more of the story, I actually edited in the parenthesis portion of my reply to point out that he had mentioned he was doing pulls because I noticed it wasn't mentioned here.

 

Thanks..

And then some people wonder why, we get frustrated when people ask questions and think we somehow can just magically know all the details.
I saw a thread on here about were all the "POSTS" have gone etc, and this is part of the problem, for the OP to make QUESTION he did, is 360 degrees from what is actual issue is.
I guess some people dont realize that , like myself dont work here, nor get paid to read post, or reply or to research to try and assist.

The reason I do it, is because when I did have a question before, there were people that helped me out alot, and I thought that "wow" if this person took the time to help me, then at least I can pay it forward and help as well.

But then you get questions like " My car makes a noise, whats the problem ? " -

Hey OP, why wouldnt/didnt you just copy and paste the more detailed question from your OTHER AMG group, so atleast we had the info ? (just curious)

 

Guess he wants to know what the problem is without devaluing it. Not that anyone knows his car, but still.

Is fuel known to surge in these cars?

 

The group chat isn't on a forum, it is on an IG group chat so I can't easily just copy and paste. About what happened why it's two different stories. The first time I got the knock limit exceeded CEL code was many months ago and yes I was full throttling it. The recent same CEL code with the knock limit exceeded occurred when I was driving it on comfort. I wasn't hauling ***, I was driving normal since I had someone in the car with me. Yes the fuel was at 1 bar left, but people on here say that can't be the reason for the knock limit exceeding if i'm not flooring it. It's been more than a week now and I haven't got a check engine light since the mechanic reset it. My car drives normal, but it was also driving normal when the knock limit exceeded so I'm guessing I need to replace my knock sensors. I want to add that when my car was tuned, I didn't change the spark plugs for about 8-9k miles, that might be a factor to why my knock sensor is faulty. I've called DME and the representative advised me not to let the car go under 1/4 tank, that's why I even mentioned it on this forum. Hope this clarifies some of the confusion.

 

Ok I had the story wrong too then, I thought both times you were getting on it with 1 bar of gas left in tank.

 

Most Tuner's etc will tell you not to let it run low for multiple reasons:
1) more garabage etc at bottom of tank, and risk clogging or bad gas
2) If your running a heavy tune/mod , and you get "less" gas or run dry on a pull, you can get engine damage from it
3) on WOT , and drag pulls etc, the g's will push the gas around enough, that if you are low on fuel, then refer to #2 above.

But yes, your post here definitly was confusing to most, as that crucial part was left out :-). hope your whip is all good now, and no more issues....

 

Thank you,

She runs normal as of now.

 

Awesome......