Yes, and it sweeps smoothly and follows the voltage windows specified in STAR. I replaced it about a year ago thinking it could be a problem, made no change but I think I can rule it out as an issue.
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I've watched the voltage top out on the TB, about 30% through pushing the accelerator, and then the accelerator voltage continues it's normal climb to max when I hit kickdown. The voltage goes up when depressed, then down again on the way back, unlike the TB that fluctuates all over the place.

 

Hey, if anyone is still following and feels like doing me a huge favor - could you pop off your intake pipe at the throttle body (should be easy if you only have one clip left on the connector as many of us do), and turn your key to the on (not start) position? Then go watch the TB butterfly. About 20-30 seconds after turning the key on it should start clicking, close all the way, the flick open and back closed again. It shouldn't matter what throttle body you have.

What I'd LOVE to know is if yours goes all the way open, and not 20% like mine does.

I'm basing my assumption on the fact this is how the TB learns its stops according to WIS, but Mercedes doesn't lay out exactly how that happens as that's in the software programming.

 

just tested my stocker it just jiggles like twice maybe opens like 15 to 20 then I think I hear the bypass valve doing same inside and then nothing

 

Thanks PieRat! OK this is interesting then, I can now ignore that as a symptom despite the rest of the problems. Since I have my throttle body off I can also watch the bypass valve, it happens to open all the way and go back again, hence my thinking the TB would do the same but I guess not.

 

Alright, time for a plan.

I tested the TB readings again tonight, along with the accelerator pedal values according to WIS, and readings are all ok. I still get voltage fluctuations on the TB (where as the accelerator pedal is rock solid on voltage values to the 100th dec), but the overall readings on both potentiometers are within the acceptable range.

Given the history of codes, and it's a short list, I've had faults for the bypass valve and MAP sensor. Despite replacing both, I didn't toss the old bypass valve and decided to plug it in tonight and run all the tests on it, and it passes which tells me that past code could have been an anomaly, but was triggered due to an unacceptable voltage value given other engine parameters. I also had the bypass valve (new one) stop working once and had to unplug the battery to return it's function to normal. I get spikes (my original post) in multiple electronic components, all things under 5v and on the same wiring harness. Battery and aux battery testing fine, all fuses good. The car spent a brief time not starting on first try, and I had to replace the crank sensor a year ago when it died on me and coded, but again it's the same harness and that is voltage the ECM relies on. Too many uncommon coincidences.

I'm going to order and replace the main harness, it's a bonus for me to get new connector tabs everywhere and given the scope of 'weirdness' surrounding these issues I can't ignore this could be a main culprit (and as E55Greasemonkey pointed out, 'investigating' the harness requires cutting the main insulation and would ruin the integrity anyway).

This requires removing the SC, so I'll reseal EVERYTHING again while it's off, and I might as well port the snout and install a larger TB as this is hopefully the last time I have to have it off. It would also eliminate the possibility of my two throttle bodies being bad in the same way, which is unlikely but still possible.

Parts being ordered shortly, and I'll likely tackle this next week after turkey day recovery. Wish me luck, and I'll be sure to update once she's all back together and I can re-run tests.

I've had to drive my old '95 M3 the last few days, and have been really appreciating a platform that uses cable throttle and doesn't even have OBDII. Apples and oranges, but I like appreciating both ends of the spectrum (and it's too darn cold to ride my motorcycle!).

 

Last random idea for you; check and clean the main engine ground wire and terminals. It's underneath the car, I'm pretty sure on the driver's side going from the floor pan to the transmission bell housing. If your car has corrosion underneath the ground cable may need replacement.

 

You know, I was going to ask about grounds as the WIS documentation is not the best. They mention the smaller one off the power steering pump to the drivers fender area but not much else and it's been a little while since having it up on the lift.

 

Thoughts? It's not the worst I've ever seen, but given the cost and ease of replacement I'll replace this too.

 

To rule out or condemn the harness, voltage drop test the wiring with a load. It's hard to do in this scenario, but I usually use a light bulb to "load" the wire, and perform a voltage drop test across the suspected wiring. Resistance checks will only get you so far, and can lead to a possible misdiagnosis. That ground strap doesn't look great. You can easily test or replace that or just add another ground with a short strap from Pepboys or the likes. With so many variable (ie. the tune, mods, etc,) you should start with the "physical lair" first and then move onto magic boxes and components after you know the wiring/pins are good. Ive seen spread out pins, chafed engine harnesses causing shorts, corrosion, and smoked control units.

 

How are you making out Gin ?

 

Waiting on supercharger gaskets etc to come in before I pull it, things were delayed due to the holiday, so currently I'm hanging Christmas lights haha. I have a short trip over the weekend then hoping to dive in next week when I'm back if work isn't crazy. Updates to follow!

 

Thought I'd post an update, and boy it's a good one! The picture below says it all, and I feel very content having pulled the trigger on a new wire harness. USPS has been dreadfully slow bringing parts in, rubber grommets and odds and ends, and my machine shop fell through so I decided to tackle porting the supercharger snout with a carbide bit myself (and am pretty pleased at how easy that was) so it's now going back together. Finding these wires split (and the whole harness is brittle as a rock), plus the bypass valve rubber grommet collapsed somewhat again, I'm confident I'll have a whole new beast when she's back together. I'm just waiting on a coolant temp sensor (the LAST thing that hasn't been replaced under the SC haha) and then it's a half days work. Soon!

 

That's great news!! If you can call it that LOL.
The top wires actually look broken too.

 

What part of the harness did you find these breaks in?

 

That picture is where the harness splits off below the front of the supercharger and runs to each head. That particular side serves the right cylinder head ground, injectors and coils, coolant temp sensor, cam sensor, and alternator and starter ground.

I didn't spend much time investigating other parts once I saw that, it just went directly into a bag and up on a high garage shelf with other relics.

 

FIXED!

Finally got her back together last night w/ proper set time for RTV, and of course it starts snowing... But today I got her on the road and in the scenarios where I could get it to dump boost and act up, it just boosts more! I'm so pleased. The 82mm TB on initial tip in feels great too, roads are still too nasty to do anything over 50% throttle so I can't comment on power gains yet, but driveability overall seems smoother and more responsive.

The other interesting thing I noticed - during all of my electrical testing, the TB learning (snap open, snap closed) after the key was in position 2 ALWAYS happened 20-30 seconds after turning the key. Now, with the new wiring harness, it happens almost immediately after keying on. I feel like I just unclogged the electrical arteries of my car haha.

If anyone else ever finds this thread and has to go through replacing the wire harness, I have some tips and tricks, but hopefully my car was a rare occurrence of this. Writing these down before they disappear from my memory.
Tips:
1) You don't need to purchase the extra TB extension harness, the regular harness reaches the TB no problem. And that harness is the one with the blue tape on it, don't plug that into the bypass valve.
2) Speaking of the bypass valve, if you are fitting a larger TB adapter plate, plug in the bypass harness BEFORE sealing that to the snout, the harness won't clear it once it's installed.
3) Instead of removing the alternator on the passenger side to thread the wire harness down that side, cut the old alternator plug, loosen the lower alternator mounting bolt (that holds the bracket for the wire) and pull the old wire back up from the top. Then, on the new harness, use a pick to carefully undo and remove the wires and female pins from the connectors (wire w/ the stripe goes to #2 on the connector). Then you can feed the new harness wire down with just the pins on the end (tape them up so they don't get caught or scrape on anything), then simply re-insert and reattach the wire connector from the bottom of the car. It's tedious, but will save you at least an hour vs removing the whole alternator to make room.

Also, if you happen to have a kids bike trailer with the little whippy flag on the back, the parts of that flag make great centering dowels for reinstalling the supercharger (see below)

 

I'm happy for you man . That was a long haul for sure !!!
It sucks that all us are all over the map and we can't get together to fix issues like this. But it's fixed that's all that matters for sure.

 

Glad you got it worked out. I’m sure you’re happy to get this behind you. Plus this info will hopefully help someone in the future too.

 

@GinDistiller before you move on from the m113k, did the wiring harness finally solve your 82mm throttlebody issues?

 

Annoyingly the issue was 3-pronged. First was the wire harness, that definitely fixed the mechanical loss of boost I was experiencing (and full voltage spikes on several channels). My wire harness was coming apart at the 'y' under the supercharger, so much heat under there and the sheathing was brittle as plastic. So, new harness and knock sensors while I was in there and timing was happy again too.

Second, was tune related. I know there have been a lot of recent posts around the hiccup issue lately, and while this thread was started on something similar, but not the same, as the common hiccup, I still experienced it later on. This was after just starting off from a stop, I worked with Tony at RaceIQ, he sent me a new tune and it went away. He seemed surprised that it worked, whatever it was, but was happy. So if you don't have a RaceIQ tune that might not be a bad idea to try. I have a fixed pulley which I think was part of the reason why I had that torque pull-back at lower speeds.

Third, and lastly, was going back to a stock TB. I ran the 82mm for a while that made great power but left triggered codes pretty quickly in the ECM (not setting the CEL, but coding nonetheless). Fuel trims were all over the place too. Switched to an 80mm, fuel trims happy again and it was much improved. I ran that for a while, but I would still get the random unexplainable feeling the car was cutting power from me. AFRs have always been great so it seemed like a mapping/backup map issue with some timing safeguards etc. I finally went back to a stock TB and have had no issues whatsoever since switching.

So, in summary, 82mm TBs just plainly don't agree with some cars. I have an '03 so not sure if the first year was more prone or not. Best of luck sir!