Using an Auto Logic interface, the system is stating a misfire in cylinder 1 and 6 yet the car is running smooth and making full HP. Tried to clear the code but keeps coming back. Anyone experience this?

Thanks in advance!

 

So with the auto logic, you're pulling a P0301 and a P0306 consistently? You delete these two codes and they come right back (or they take a minute(s) to repeat)?

On misfires, these can be caused by either (or both) ignition issues or fueling issues. Ignition issues can be spark plugs, coils, associated primary or secondary wiring feeding the ignition source. On the fueling side, primarily fuel injectors can contribute to misfires either by becoming clogged or dirty causing an intermittent fueling void, or by leaking injectors that start to dump fuel when it isn't required. Also, an intermittent electrical input to these injectors could cause the problem.

The algorithm the EMS uses to measure and determine a misfire has a counter and a timer. There has to be a "number" of misfires and within a prescribed time to set a CEL. So, if you're getting the CEL returning consistently these two cylinders are showing some consistent issues. The only other possibility is an ECU that has gone defective (not likely). EDIT: And I should have listed that the CPS delay could be set too sensitively.

With the limited info given, and since you say that the engine runs smoothly and has full HP, I'd have to take an internet guess and start with fueling. Weak coils and or bad spark plugs would likely get worse under harder performance, but a leaking injector wouldn't necessarily.

 

Try this with your fuel tank down to 1/3 of it's volume put a can of Techron fuel injector cleaner (from any O'Reiily, Walmart Etc.) add 12 gallons of fuel and take the car for a spirited drive.
I just went true the same experience (even changed a coil pack before doing this) and still got a misfiring message. After this simple treatment all misfiring went away ones Techron cleared my injectors.

Best H

 

The Techron treatment is a good place to start and simple. Techron has worked in situations like these, sometimes. If not, at least you tried the easiest solution and the Techron is good stuff.

Techron is sold in parts stores and Walmarts in two strengths. There is a gray bottle called Fuel Injector Cleaner, there is a better version, the black bottle called Fuel System Cleaner.

They're both Techron, but the Fuel System Cleaner in the black bottle is a higher concentration of Techron. I've been using Techron regularly for 3 decades now. It's a good product for ongoing fuel system maintenance, and can be had on a regular basis just by purchasing gas at Chevron stations. But, buying a bottle and adding it to the tank (a full tank), occasionally, gives a little extra. By occasionally, I mean once or twice a year.

One caution though, I strongly recommend following the dilution instructions on the bottle. You don't want to keep a high strength dose of Techron in the fuel tank and the system for long periods.

Look for this product (Concentrate Plus):

 

Thanks to all for the feedback. The Check Engine Light magically went off yesterday. Planning to add some Techron to my GTS diet.

 

When I took my GTR to the dealer for P0301 they said apparently this is a known issue on the GT, P030185, P030022. PER TIP DOC# GI54.21-P-061775, Software update and scn coding on engine module, power traiasn moudule and trany module due to software issue.

They told me if it comes back they can change all spark plugs under that known issue even if the car is not in warranty.

 

Update to this thread...

The check engine light mysteriously went off for a little while, then it came back on. Taking the advice of others in this thread, I ran the tank down to one bar on the gauge, poured in a bottle of Techron, added 12 gallons of fuel, applied liberal amounts of right foot pressure and voila... the check engine light turned off after 40-50 miles and has not returned since.

Thanks to everyone on the GT forum for the continuing education! Forums are SO MUCH better than social media.

 

That's good news! Nice when the first shot takes the issue out.

 

do you recommend the 12oz bottle for a tank or the 20oz bottle for a tank ? looking on amazon to get some.

 

It’s weird that Mercedes Canada says the misfires are a common issue and they have a software fix for it which they updated my 2018 GTR too.

 

Well, if you're trying to fix a problem Techron can work in more concentrated doses for a temporary period, then further dilute with more gasoline. It's bottled in different sizes for different size tanks.

If you're just adding it for ongoing use, the dosage recommended on the bottle is best. It's about 12 oz for about 18 gallons of gas. The 20 oz bottle would work for a much larger tank. I only add a 10 oz bottle of the concentrate to my cars about once a year because I get Techron in my gasoline at the pump all the time so I am using it always.

Techron is fairly safe, but you shouldn't go crazy with high concentrations for long periods left in the tank. It can be a little aggressive and really unnecessary in prolonged high concentrations.

Hope that helps.

 

mine would just be once in a while to keep the system clean. I think my car has a small misfire, I can feel a slight tremor when stationary maybe due to my Stage 2 tune... not sure, I need to go pull logs. But I figured at 35k miles its probably due for a clean (I bought it used).

Grant

 

In these cases, misfires are not real which could very well be Propdyn's situation too (We'll see if his fix holds). So, in his case, if he reports back here that the misfires came back again and he's sure there isn't an actual failure with ignition or fueling, then he could have the same issue.

I've seen it in other manufacturers. These are not real misfires. It's that "thresholds" on the delays the ECU sees through the Crankshaft Position sensor is set too sensitively. So, they create a simple SW patch to modify the data table the ECU is using to measure the delays. A lot has to do with the ways a particular engine is wearing in over time. Maybe the misfires start to appear in one car out of a high number of cars, enough that the factory creates the patch. It won't be a general recall, just cars coming in with misfires showing up, but they are not real misfires. They apply the DT change which modifies the threshold and the misfires magically stop appearing BC the ECU is no longer responding to the same sensitivity in crankshaft delays.

 

My guess is you're feeling the tune as the change in CS speed the ECU is using to pick up misfires is like minutia compared to, lets say, pulling a coil primary plug which would be a genuine misfire and would make the car shake.

Th other thing that I see sometimes, and here it's important to say, I am not trying to impugn ANY tuner anywhere, is that some tuners will simply desensitize certain ECU functions so their tunes (toons) are not constantly setting CELS or responding to ECU corrections. Lots of ways tuning is shortcutted BC it's easier to change a threshold or sensor sensitivity so the ECU doesn't respond. I've seen it on knock sensor timers and delays to stretch out the high octane timing tables rather than putting the time in to get the timing table correct. NOT good.

 

what do you mean by CS speed ? I feel the "shake" at idle but its subtle, like when you're waiting in your car on a bridge and the bridge moves a little as traffic rolls over it. I have the eurocharged tune and im my experience across a few cars they have done a good job, but I obviously haven't analyzed their tunes..

 

So, the ECU uses the crankshaft position sensor to determine where any cylinder is in its combustion cycle. If a misfire occurs, at that moment, the ECU will see a brief interruption (delay) in the normal (expected) CS speed, it logs it as a misfire. In the next cycle, if the same momentary delay in CS speed occurs at the same position the ECU logs another misfire count assigned to the cylinder it recognizes at that place. The EMS designers determine how many logged delays should set a misfire CEL. Also, once a log is started, if the misfire doesn't repeat in the next cycle (or number of cycles) the ECU "forgets" the logged misfires and starts the count over.

It's that delay I was describing. The ECU can respond to delays you wouldn't necessarily feel, seat of your pants.

And, the shake you're feeling might not be related to a misfire. Could be where the tuner set the VVT, if they modified it.

 

I concur with "Acta" on how sensitive the inputs to the ECU on these cars make a huge difference on how they perform. Having dealt with a none existing engine oil temperature input to the ECU and a misfiring issue on Cylinder 1&2 myself and experienced the effects it had on my engine you only have to watch this video to understand to what length AMG goes to make it all work right. The answer is best described by the German word "Punktlichkeit".
I believe that any the amount of time, research and money that the factory puts in is very hard to match for any after market tuners.


Enjoy your car.

Best H

 

Thanks Hendrik for that fascinating video.