C32owner

Good luck hope you get some good news.
Not sure on the tune. But if you were tuned to run a 76mm and now you back to stock that is quite a difference and the tune might affect things. Not sure how much leeway the ecu can adjust for lower boost when tuned for high boost in essence. Again an afr Guage at the least is your friend. Think play it safe and don't wot it...

PieRat

Just flash your stock file back onto the car mate. Then you have matching ecu and moda. Ecu tune shouldnt be fixing any engine problems caused by mechanicl faults.

Is the car running fine when in open loop (aka wot)? If it is is spin the supercharger by hand, how does it sound/feel?

Lekdown/compression test, then try work out what input to computer is bad..eg map iat o2 sensors, injectorz, spark.

you seem mechanical but sometimes a good factory trained mechanic might save you time and money in the long run?

lockeed

I invested my Sunday afternoon in pushing the diagnostic a little further... So as suggested by other members, I went back to the OEM ecu and pulley. Went for a test drive, couldn't get the car to jerk or hesitate. Car ran strong. At WOT, it pulled steadily towards red line. Doing a 3rd gear pull at 50mph, gradually opening throttle to WOT didn't produce the usual hesitation and engine vibration of the VRP setup. All in all, stock pulley and tune works as it should, no CEL.

Came back to the garage and swapped the stock pulley for the VRP one along with the shorter belt of course, but I kept the stock ECU. Went back on the road, at first car seemed to run OK. Flooring it, engine grabbed and pulled as it should but produced a more noticeable belt squeal. I tried 2 or 3 WOT passes, car seemed to run pretty good but not as good as the OEM pulley felt. But the 50mph 3rd gear pull really brought back the symptoms. Anywhere between 1/2 to full throttle in 3rd, I felt the usual hesitation and vibration.

Worth mentioning again that the car has just been to the dealership where they replaced the fuel tank, pumps and level/sensor under the warranty extension, and I just replaced all plug wires for good quality ones.

The only thing I didn't try was running the car with the VRP tune and stock pulley, which might be worth trying, feedback welcomed. So far - and this has been my feeling from the start - I feel my VRP pulley is somehow defective or not within specs.

PieRat

Yeah sounds like your pulley is bad. What tune did VRP sell you? I imagine its EC or RaceIQ.. Both are reputatable and should be fine.

u should try return it for replacement or refund...also could look at getting a tuned version for stock pulley to run in the mean time..

lockeed

I explained the latest tests to VRP, and they accepted to have the pulley sent back for inspection.

I'm hopping they'll find what's wrong with it and fix it, or replace it.

Das_it16

Did you ever get this resolved?

lockeed

Not really. When I stored the car in Nov, it was still hesitating under wot. I'll need to push my research further...

corvettekro

Hi Lockeed.
New member here - I just stumbled over this thread. I think you need to check your fuelpump electric connection - even if you dont see or smell any gas. Here is why:
The M113K engine is fed by two 5.2 bar fuel pumps in a continuous flow system (the fuel is constantly flowing in a loop and the fuel injectors "taps" the fuel as per demand - the rest is sent back to the fuel tank.)

A common weak point is the fuel pump connection on the fuel pump cap of the fueltank. What happens over time is that the integrated metal in the cap corrodes and causes more resistance. This again causes more heat
and so it continues over time until the electric connection gets so bad that either the wires or the plastic cap melts.

Then one fuel pump most likely looses its electric connection and as such becomes inop.

Now the engine is fed only by one fuel pump, and that is okay for starting, and normal driving. But as soon as you open up the throttle - there simply isn't enough fuel pressure to supply demand and the engine
now runs lean until the point where it misfires. As soon as you back off the throttle everything is back to normal.

So I would recommend you to check this again - using caution:
- Disconnect the battery
- unscrew the metal cover
- knock loose the plastic ring that holds the fuel pump assembly in check.
- static discharge yourself.
- remove the cap with the electric connector and pull it up and out.
- Now inspect closely for any "burnt" area or scoring.

If you are lucky - you can take a piece of emery cloth and clean the connection with some contact cleaner. That worked for me. I had exactly this problem.
Hope this helps.

lockeed

Thanks for the heads up, that's realyl apreciated.

However, MB just replaced my pumps (recall) last summer before I stored the car for winter, I would assume they checked the quality of the connectors before replacing it, or they might've replaced them entirely...? What's the "usual" extent of this repair under warranty ?

corvettekro

Well...... I don't know about warrenty. Normally the fuel pumps comes as a complete assembly and is fairly pricy (about 500.- USD).
But it could be that the dealrer just changed the harness - that is a recall item if my memory serves me correctly. There have been many cases where the wiring has completely melted inside the tank.

I would go and check - it free, its fairly simple and not a difficult procedure.... just leave the pumps in the tank.
You should be able to clearly see if any scoring..... takes about 20 min to do.
Just be carefull not to static ignite any fuel.... Run the tank almost dry.

Good luck

Aditya Prabhu

Damn...have the same issue on c63 w204.

tried all of the above

@lockeed so when you go wot...redline shift...gear shifts bogs down / hesitates / sputters...feels like lack of fuel or power...overall acceleration and torque is low ?

pinning towards a torque converter issue...will check mine

what’s your status as of now ?

lockeed

last time ai drive the car in Sept, still had these same symptoms. Haven’t had time to investigate

coobah

Sorry for being here but I just need to know it.

Could you please tell me what is connected in a place marked on this pic???

the_indian_kid

Going through a similar issue on my 2014 c63 supercharged and cammed and 1200cc flow matched injectors.

No cel. At wot, car hits about 6000 rpms and sits there until ecu activates fuel cut. But if you give it almost half acceleration pedal or less (slow acceleration), it goes to redline aka 7200. If i accelerate slowly past 6000 and punch it, the rpm cut happens again.

No cel, no indication nothing. Did have few misfires time to time though while driving normal.

Also having hard starts requiring bit of gas pedal upon second start and onwards of the day. First start of the day always perfect.

Used a xentry and from my understanding, showing ecm detecting sensors voltage either not consistent or out of their range high/low.

Torque app on the other hand, shows injector code, throttle actuater code Sensor A and B, and few others.

Its driving me nuts..almost sounds like a electrical / computer issue. Its definitely not the tune i can tell you that.