Here's a timeline...

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~1 month ago - Nasty surging started at idle/low cruising speeds after cleaning the boxes/filters/original throttle body while removed from the car (Q-tips, TB cleaner, barely moved the butterfly). Idles very high while in R/D; really have to stomp the brakes to stay stopped. When in park/neutral, the car surges up to 1800-2000RPM, drops to 1000RPM or so, then surges back up. Also, when you hit the gas while the car is idling normally, half the time it surges up to 3KRPM, then keeps climbing to 4KRPM for 10-20 seconds until it drops and starts doing the surging. Car is driveable, but a pain in the ***.

Three weeks ago - Replaced the wiring and TB-end connector (the one that plugs into the actuator). Tested the wires for voltage/continuity and triple-checked the hookups. Made no difference at all.

Two weeks ago - Car sat for a week while I was on vacation; rainy weather the whole time. Started up the car and it was surging/idling so bad that I could hear the belt skipping/chirping from within the car. Tried to calibrate the TB (key position two, wait five minutes or until the sound stops) and that led to the ESP "Visit Workshop" CEL + limp home and a new one - rough, trembling, hesitant idle. I believe this is being caused by the new throttle body not having a chance to get calibrated.

One week ago - After bringing the car into a reputable place that I get some work done and having them pull codes from the PCM saying the TB and/or the actuator are misbehaving -- Road tested vehicle to verify and reproduce condition. Interfaced with engine control computer. Recorded diagnostic fault code P202E-008, P2032-008. Performed pinpoint system testing and diagnosed faulty throttle body.

Replaced the throttle body with same P#, but newest revision. Shop warned me that a new TB would require reprogramming of the PCM but I think they were just blowing smoke up my ***. No change at all, except for the smoothness of the idle going completely to hell.

Tonight - Replaced the wiring again, this time with a complete and whole new unit, here. Left the battery disconnected for an hour before/during replacing it and let the TB calibrate for five minutes after hooking the battery back up. Still no dice.

Few other details here - https://mbworld.org/forums/c32-amg-c...ml#post5363288

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At this point, I'll gladly buy someone beer/weed/nachos/midget strippers/whatever they like if they can even point me in the direction of somebody with a STAR Diagnostics computer that won't charge too much to pull/clear the codes in my ECU and see if anything else shows up. Just the same, I have money to lay down on some serious or lengthy troubleshooting if needed and would rather do that and have a more accurate guess at what part(s) is/are malfunctioning. It seems like a much better option than just calling a flatbed to bring the car to a stealership and have them hook up a STAR machine for ten minutes while they laugh at my rusty trunk and charge me $300.

Even halfway educated guesses at this point would be appreciated. I've read through every thread back to 2007 or so about crappy idles, throttle bodies/actuators/wiring, ECU codes... and I still can't come up with anything else.

 

And now the car has a P0120 Throttle/Pedal Position Sensor/Switch A Circuit Malfunction while running, but it's not storing it.

 

Have you tried SpeeDriven in Palatine?

 

Nope, but that's not too far from me. I'll give 'em a call, although I don't know how much interest a company charging $1100+ for a C350 tune is going to have in fixing a ten-year old C32. If they're as "passionate" as they claim, maybe they'll help

 

Any good mechanic should have a diagnostic scope to help them trouble shoot where your problems are coming from. I don't think you necessarily need a STAR machine. Esp. if your problems are happening all the time.

They should be able to run leads from your TB wiring harness onto a Scope such as this one and figure out where the faulty signals are coming from.

oscilloscopes

I think you should hit up some reputable indy Benz mechanics and see what their diagnostic plans would be.

 

I haven't done any performance tuning with them, only Service A/B so far and some maintenance. They don't make me feel as if I'm wasting their time or keeping their hands off much more interesting projects. They charge significantly less than what a dealership would too. Give it a shot. Look for Marcin when you call. He's a very knowledgeable guy.

 

Ok, cool. Thanks for the recommendation. From their prices and high-end sort of focus that their website seems to portray, it almost seemed like my issue would be small beans compared to their usual stuff. I'll definitely check into taking my car over there.

 

Wouldn't it be worth clearing the codes out of the PCM?

 

That would also be able to read the hidden codes and clear them too...

 

A 'scope that can clear ECU codes? ****, I'd buy that in a heartbeat!

 

http://www1.snapon.com/diagnostics/us/vantagepro


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here's a used one for a grand:

http://www.ebay.com/itm/SNAP-ON-DIAG...667c27&vxp=mtr

 

Damn tempting... I'll get one *after* I get the car fixed ;-)

Anybody else with good recommendations for shops around Chicagoland, preferably the N/NW/W 'burbs?

 

http://www.benzshops.com/illinois/benz-tek

 

They are very good at SpeeDriven and have worked on my car a ton!!! Great guys at SpeedDriven. Marcin is very knowledgeable as well. FWIW, a tune on a C350 is not as easy to do as it is on a C32.

 

So, it turned out to be a vacuum leak after all. Apparently, the hose that hooks onto the bottom of the throttle body was pierced/severed lower down where I couldn't see it. Plus, the TB needed a new gasket (who knew metal gaskets go bad...). All in all, an easy repair for the guys over at Speed Driven. For anybody in Chicago, I would DEFINITELY recommend these guys.

Alex and Martin have been nothing but amazing in answering all my questions, plus just for shooting the **** and giving advice on what type of car to upgrade next. Plus, if you can't trust a shop that you walk into and see a SL65, CL65, CL600, S65, E55 + two 996 911 Turbos in, then you can't trust anybody

Props to Newz/CheDeng for the recommendation, and to GrammaBenz as always for being a great source of ideas/info =)

 

 

Oh yeah, that's the other thing - their labor rate is only $90, and they don't overcharge you on the hours at all. For them to pull my TB, test it out, test out the old TB, hook up the computer, clear the PCM codes, replace the vacuum tubes and gasket, then test drive the car and knock out one other little thing, they only charged me 1.5 hours of labor. Talk about awesome!

 

Pm'd hopefully we can help you out