Roverron

from what i have seen it is the timing between the bypass flap and the TB which causes this issue. once they are in sync you will not have the hiccup anymore

LandCruzer94

The issue that I was having with the engine wanting to die after my drive to work has a peculiar sound coming from the throttle body when it's happening. Sort of a clacking noise. If I could envision it inside there it sounds like the plate is bumping against the stop. I've been watching the vitals on Torque and the throttle ℅ drops to about 1.6 I think followed by a jump higher. Vacuum is dropping around the same time but I can't tell if it's because the throttle is opening or if the throttle is trying to compensate for the leak that happens first.

It only seems to happen if I cruise to work and give it a big dose of throttle as I position myself to get off the freeway. Similar to others experiences when the issues come up.

If I don't have a wideband can I watch my short term fuel trims to look for a +25% spike and set a warning for it?

JoeJErnst

That's been my hypothesis all along. Now the question is, to adjust the bypass flap do you use STAR, or do you need your tuner to do it?

carguyshu

STAR I believe does both when you do a full reset

210lvr

It would make sense that the bypass valve is a culprit as I only started getting the hiccup after the supercharger pulley. The pulley requires a change in the bypass valve control I would imagine but again I'm not a tuner. Makes sense though as the ME is probably going to want to bleed boost off when it sees the increase from the pulley. There is a lean spike and hiccup but there is no continual lean mode. Once I install the tb and tune then I get this persistent lean loop of extremely lean for an extended period of time then rich for a bit then back to lean. The little hiccup I'm not worried about, the lean issue is what worries me and is dangerous. I guess we should be more detailed on what we're talking about since I think some have a hiccup that isn't really dangerous and others have one that you should not be driving with IMO.

LandCruzer94

If it helps, I pulled my codes in STAR yesterday. Two stored codes for "B28 (Pressure Sensor) Signal Implausible" and I took pictures of the snapshot data when it occurred. They're bad pictures so I'd have to type it all up, so I'll make sure at least someone would benefit from it before cluttering the thread

jmb614

Did you run it throught the B28 pressure sensor tests in STAR? Blip the throttle and see if the pressure value goes up, if it doesn't change much likely a faulty sensor.

LandCruzer94

No but I will, that's a good idea. Thanks!

Roverron

B28 (Pressure Sensor) Signal Implausible
your getting that code because the signal isn't correct for the tb position and bypass flap position and the value of pressure. so it tries to correct then throws a code. the sensor is fine its just that the value is not in the code for the ME

you get the lean because TB tries to reset

jmb614

So what is the procedure for synchronizing the TB and bypass; is it in STAR?

Running the test in STAR is done while stationary, it certainly won't hurt and is available to indeed show whether or not the sensor is responding.

I've ran the 82 for well over a year, with the same tune, and never got the code until recently. Ran the pressure sensor test in STAR and saw that the sensor barely moved.

So either STAR is lying or the sensor is bad.

210lvr

right, my idea was just that the relationship between the two was off. For example if atmospheric pressure is x then at y tb position and z bypass position b28 will/should read a known value. So installing a larger tb would cause the value to be off (bear with me I'm no tuner). Not necessarily that the sensor in the ME was bad (can't be since the issue remedies itself when installing the old TB) just that the relationship between them all was not right. Since I've posted this thread though and been thinking about it I have a feeling that I may be giving this sensor more credit than it deserves and it doesn't play a role in anything other than altitude/ambient condition compensation. I do wonder what code it would throw if we somehow changed this sensor signal to an implausible value. I have a spare ME but I'm not sure I wanna potentially damage it to find out.

jmb: I have not seen any other way to sync the valves besides default initialization. I think syncing them to match each other after the mod must be something that is accomplished with the programming in the new tune.

jmb614

Iirc leaving the key in the number two position for 60 seconds will allow the TB to run an adaptation, but I don't know if that is the same as it syncing with the bypass. I'm sure someone more knowledgeable in STAR etc. would be able to specify.

LandCruzer94

I think if it's in position 2 with the TB unplugged, and then plug in to get the TB to start the adaptation for (roughly) two minutes. Then re-cycle the ignition.

jmb614

I'm aware of that process, I am speaking to the synchronization of the TB to bypass as well as where in STAR are the options to perform those functions.

Roverron

you have to do the sync in star
the key sync is only for TB

LandCruzer94

Bumping this up since I found a YouTube video that might be helpful. This is for a C class kompressor but the function M16/7 sounds like something used with m113k cars too.

https://youtu.be/zLvSkPLUDxI

My battery has been charging all weekend so I haven't had a chance to verify its in STAR
yet but I will tomorrow.

LandCruzer94

Late bump, I can't find a bypass reset in STAR, looked for a couple of hours in the menus. I don't speak German so perhaps it's in the development menu. Anybody have any more thoughts?

VictoryRoadPerformance

Contrary to popular belief these throttle bodies do go bad. That is why we offer a warranty with all the throttle bodies we sell. Did you use a bolt on plate or weld on? The major advantage of the bolt on plate, and one of the many reasons we opted for this approach is being able to swap back to stock TB in minutes to see if the TB is infact the issue. there are multiple ways in which we've seen these TBs fail as well.

LandCruzer94

To my knowledge it's a ported SL55 Snout, so I'm not sure that it would be backwards compatible with a smaller TB. I have a newer gen MAP sensor that is waiting to be installed, but I had a lean surge this morning on the way to work this morning with no codes and it's pushing me to find a resolution.

carguyshu

the TB learning procedure should sync both

210lvr

i have never seen a new tb go bad but I only work up to factory spec meaning all stock cars and the tbs have never been removed or messed with until it gets an intake manifold lie all the 272/273s (I assume everyone is using one of these as am I).I personally have not replaced 1 in a decades time and I have only seen 1 that needed replacement by another techand it was an sl55 that would get an surging idle back and forth constantly with no throttle response just the plate moving back and forth. It's rare we see anything modded at the dealership level. I'm a new age tech so yea, we don't quite know everything the old dogs do and I'm sure you've seen more than I. I don't have an engineering background so my skill set is just grease monkey level

You being aftermarket and custom work I can imagine you've seen some failures. What kind of failures have you seen?

I just can't see all these tbs being bad. Please enlighten me, I don't think I'm too smart to take advice.

i have the bolt on vrp adapter using the mb sealant to seal both ends. I have removed it and went back to stock and have no issues since.

ideally I should try a new in box one but that would be a special order and well yea, we need to set some limits here lol

Rocman8

+1 in over 10 years I've also never replaced one or seen one go bad on any Mercedes except a 120 engine.

carguyshu

I bought an 82 from a low mileage junkyard car and it was bad. bought another junkyard one that was high mileage and it worked great.

VictoryRoadPerformance

we have seen a DOA rate of about 6% on used throttle bodies,

the issues Range from stuck or sticky actuators (slow closing) (repairable) to throttle bodies that put the car into a limp mode but still function (at this point not repairable)

surging is more likely a leak post TB.

a common cause of the p0505 is the gasket ring on the bypass valve being seated incorrectly or the metal tube on the drivers valve cover.

Ive heard a number of people say the same thing "Ive only ever had to replace one" I believe the 82mm TBs are more prone to failure than the 74s. We have never had a customer purchase an 82mm kit due to having a bad 74mm. Another problem i'm sure is that these bad 82s just keep recirculating. Ours go in the trash or to be repaired, but where do the others go? We have never had an 82 that we have sold go bad, but like I said we see them DOA every once in a while.

Our TBs are certified used parts, and we offer a 90 day warranty with them.

VictoryRoadPerformance

Bingo.