Misfire after weistec tune
I have Autel MS906TS which I was using for diagnostics. With the Weistec tune I get knock at high RPM, on the stock tune I don't. Shift points on the Weistec tune moved past redline- I crash the rev limiter if I don't manually shift. Nothing is wrong with the car running on the stock tune.
I contacted a reputable company in Florida- They're willing to give tuning my car a try.
But instead I have to buy HP Tuners MPVI2+ and tune it myself to prove I can.
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and for fun here’s my car too! Love it!




So the whole misfiring issue was all because of this shi*ty little plastic part all along?
it’s the whole piece, the two solenoids, tubing, and sensors very front of drivers side engine bay. but yes lol. It can cause misfires especially at high rpm because of its function and it’s just a stupid emissions device. All this headache and trouble for months. Weistec took the car and figured it out when MB couldnt. Went from down on power misfiring to beating dodge demons on race gas. One stupid part.
Ok now i'm paranoid mine need replacing you wouldn't happen to have any part no(s) or diagram of what these actual parts are? wanna get mine sorted with new ones while i'm trying to rule out a persistent misfire issue of mine too 😓😓😓
George
Ok now i'm paranoid mine need replacing you wouldn't happen to have any part no(s) or diagram of what these actual parts are? wanna get mine sorted with new ones while i'm trying to rule out a persistent misfire issue of mine too 😓😓😓
George
FYI: From the dyno graph you posted, you're making 519 hp and 618 ft-lbs of torque.
The Best of Mercedes & AMG
Last edited by domjansson; May 12, 2022 at 11:52 PM.












What you guys should do is try to get the fuel purge vapor & PCV ( Positive crankcase ventilation ) schematic.
Unfortunately the document Introduction of Mercedes-AMG C 63 with Engine M177 Model Series 205 AMG Introduction into Service Manual does not show anything. Only description and only for fuel vapor purging.
Observe the CHECK-VALVES
On my V6 3.0 M276DELA30 which is the same engine but lesser power than C43 , there are a few checkvalves which is part of the oil separator ( PCV) and Fuel Vapor Purge system being integrated into a single system.
I believe the M177 by the description on that page 47 would have such set up too. Those check valves can fail and your turbo boost partially can escape from the inlet manifold towards the PCV system or/and to the fuel vapor purge system.
The fuel purge valve is easy to verify its state of CLOSED or OPEN when not applied power. This is a normally closed valve aka CLOSED if no power applied. Use vacuum pump/gauge to test.
Look here : https://mbworld.org/forums/e-class-w...rge-valve.html
The operation of the fuel purge valve is using PWM signal, not simple ON-OFF, this is where it can go wrong. PWM signal is mapped assuming the valve is 100% healthy, certain duty cycle will equal to an X opening value of the valve.
As the valve ages , even if it can CLOSE properly, it may not open enough as commanded by ECM. Fuel mixture miscalculation can occur from this fault.
At certain period, purging a fuel vapor by this valve, the charcoal cannister maybe fuel vapor loaded, that means the ECM will caculate extra fuel into combustion chamber.
If fuel vapor is exhausted and the valve is still open as in : stuck open, extra normal air is what is injected into intake manifold and a lean condition can occur from too much air.
The fuel mapping does not take into consideration a sticking open fuel vapor valve solenoid, but some variant/market have pressure sensor to track this unfortunate condition.
My engine does not have such sensor, I believe C43 USA version has it. https://mbworld.org/forums/e-class-w...re-sensor.html
The simple explanation is this :
01A. Our engine is turbocharged. This means the intake/induction system has 2 state of pressure. Before turbo boost built up above ambient pressure, we have good suction at intake manifold up to easy approx 300 millibar or 4.3ish negative PSI.
Good suction at intake manifold AT ALL RPM RANGE like any normally aspirated engine is the easy part for any PCV and Fuel Vapor purging to be in operation, because them oil vapor and fuel are being sucked.
01B. During boost, the intake manifold is now at pressure equal to the boost the ECM commanded and that is easy 12 psi above ambient pressure.
This is when PCV and Fuel Vapor system need check-valves and diversion strategy. On M276DELA30 the Bank 1 intake at turbo ( after air filter housing ) is one of the "diversion" for the PCV.
I have no idea how M177 plumbing and check-valves arrangement are done for its PCV and Fuel Vapor, that is your homework as owners of this engine , try to get info on these systems in detail if you want troublefree operation long term.
Mechanical or electrical based check-valves or valve wil fail due to wear and tear, it has to. The higher your turbo boost, those check-valves will degrade faster , that is the cost of pleasure

Such check valves on my engine :
https://mbworld.org/forums/mercedes-...seal-leak.html
Happy turbo boosting boys......



