GinDistiller

Instead of responding to a few different threads I've started or commented on, I wanted to outline my 'journey' of chasing the annoying hiccup that a few seem to suffer from as I've finally fixed it!

Short story: Bypass valve!

Long story: No definitive codes or CELs on, just sporadic ones sometimes stored when I'd check the ECM. Experienced a frequent, although not always identical in harshness, hiccup on shifts where it almost feels like the transmission is taking twice as long to shift into the next gear. Car would bog down when given light to moderate acceleration, then take off it I stabbed the throttle and force a downshift. Because of this feeling, I chased it as a transmission problem fearing mine had glycol contamination being an '03. It was tested and didn't, but I removed the valve body and replaced conductor plate, connector, and had to replace the TCC solenoid due to a lockup problem (and it was fixed after that), but the hiccup remained.

Next came sensors: Front O2s, IAT, Accelerator Pedal Assembly, and Finally MAP sensor. No changes.

Then a code for LF acceleration sensor. Replaced, no change.

Tried a new tune and 80mm FSP from RaceIQ. Lot's more power, but same hiccup.

No vacuum leaks, fuel trims looked ok for the tune, and nothing else abnormal showing.

New TCU tune, no big change.

One day I plugged in to scan and P208D (M16/7 Recirculating Air Flap Actuator Malfunction) was stored in memory. Never set the CEL. I reset and drive a few weeks and it never came back, but it got me thinking. If that flap was not closing, and is likely moving as a shift happens to smooth out boost, it could explain the hiccup perfectly. The wiring and plug looked great, and the butterfly seemed to move freely and playing around with it, but I took a jump and pulled the supercharger to replace it.

Issues with these didn't bring up too many threads, but the one or two that did were 2003 MY M113s like mine. I'm at 145k miles. Tip: You can use a C230 unit and just transfer the rubber piece from your old unit, they are more commonly found and cheaper. I found a good used one for $60 on Ebay.

Now that everything is back in the car the hesitation is COMPLETELY gone. More torque at low rpms, and shifts are firm and assertive.

I couldn't be happier, just wanted to pass this along to anyone struggling with similar issues. And get a friend to help when pulling the supercharger, and clean the top of the engine before doing so Happy motoring!

Fountain35

Pic of the bypass valve?

GinDistiller

E55Greasemonkey

I appreciate this post, however you are confusing the 82mm TB hiccup with the tip-in hesitation problem. Let us know how the car drives in a few thousand miles once the adaptations adjust.

E55amg0220

While i can understand and relate with you on this issue the computer is designed to do just that its to regulate low end torque and make the car more docile in lower rpms due to having so much torque on demand an its suppose to be a safe guard for the trans between shifts quite annoying for those of us that have the driving skills to cope. The bypass delete is the way to go once the tune is perfected.

AMGPilot

What skills would those be?

E55amg0220

To drive an modulate the throttle properly managing the torque not just flooring it.

GinDistiller

Agreed I'd love to eliminate the darn thing. Hiccup or tip in, the issue I had is definitely gone and I've gone through 'hard resets' many times for adaptation. I know it will change as time goes with highway miles etc.

In fact, when someone asked for a picture and I picked up the old bypass valve to move it, I noticed a rattle of something loose inside the actuator motor part

Coming from owning manual transmissions for years the delay annoys me, but I understand it's purpose. Wondering if some of the tuners can at least make the flap window of operation shorter/more aggressive (or maybe they are already). One of the reasons I switched to a fixed pulley as well, I just want more predictability in power delivery, I'm not an old man who might slip on the gas pedal at any time and surprise myself

drothgeb

Unfortanatly it will still be there with a fixed pulley. Depending on how you drive if your real sensitive it's almost an unnoticeable bog but with a fixed pulley if you hit the transition just wrong you will actually lurch forward and get a boost spike lol. I had raceiq see if they could mellow out the bypass closing... I didn't notice any difference I dont think in the new tune haha. Just one of those things that comes with nodding, and unfortunately the smaller SC pulley(or bigger CP) you get the more noticeable it becomes. You can emagine how much tuning the AMG engineers must've had to do to get both a SC clutch engaging and a bypass valve closing at the same time to not be noticable. That's so much changing of the air intake path at once haha. Anyways, like 55 said you can learn to drive around it, or maybe if some one gets that block off plate sorted we can run fixed pulleys and no bypasses and have no blips anywhere haha!

AMGPilot

Might want to look into how DBW and "Requested Torque" works