jicl55

Do you have to switch pins from 74mm to Mercedes 82mm throttle body? I know you had to for the 74mm to 80mm, but I didn't think you had to for the 82mm, but might be wrong? Anyway, this is what happened:

Put Mercedes 82mm throttle body in. Got P0638 code and at idle, car goes in limp mode and shows ESP warning (white letters not red) and CEL. No power, pressing accelerator does nothing. Turn key off and on, it resets and if I'm at idle, it triggers limp mode, ESP, etc. again. Drove on freeway, seemed ok, but at idle, it messes up every time.

Idle is at 4-5% (too much) and when in limp mode goes to 7%. I did throttle body reset, etc. Bought the TB used. Could just be a bad throttle body? Wish I had one that I know works to try. Any thoughts?

guysandiego

hoping to hear info from others with upgraded TBs --

jicl55

Any ideas people? P0638 is "Throttle Actuator Control Range/Performance (Bank 1)." After a quick Google check, seems like most of the time a new TB cures the problem.... Will have to check pins and harness to make sure nothing is screwy.

I'm pretty sure no rewiring is needed, correct?

The throttle body reset is the same as the ECU reset, correct?

A couple of questions: Is there a way to check if the throttle body is bad or not? I guess I would need another throttle body to check. And if it is, is it repairable or can it be refurbished or is it trash?

blackbenzz

Are you sure it is a Mercedes 82mm TB? If so no switching of pins is necessary from stock. Make sure you don't have any air leaks anywhere

jicl55

Definitely MB TB. Didn't think pins need to be switched, but car trips out at idle, so just wanted to make doubly sure. If it is sucking in too much air somewhere, shouldn't the ECU try to compensate by trying to close the TB more tho? It's at 5%, which is way too high. 82mm are at 1-2-3% max at idle. Don't think there are air leaks, but will have to run smoke through the lines to be 100% sure.... Had air leaks on an 80mm one time and it threw different codes... P0505 and a different one, but car never did what it is doing now. ESP codes and limp mode seem common with malfunctioning TBs. Weird thing is if I cycle the key it clears the ESP warning and limp mode and as long as I am moving (not stopped or at idle) it performs as it should.

P0638 indicates actual throttle position is not consistent with inputted value. I'm thinking potentiometer problem? The only other person I can find with a P0638 code is guysandiego and he had to replace TB (I believe this to be true, but correct me if I am wrong).

shardul

iTrader: (1)

TB reset is different then ECU reset, PM Exotic-metal he knows how to do it. I can remember

jicl55

I thought it was key in "on position" (right before car starting), press accelerator, turn key off and let sit? I'll PM him, but anyone else know?

KLR CLS

Pin swap is not needed for MB 82mm TB.The only reason the 80mm and Audi 82mm needs a pin swap is because the throttle blade opens in the opposite direction. You need to reverse the polarity of the motor so that the blade actually opens. Alot of people with 82mm TBs have gotten this error. Not sure that the root cause has been found. Usually swapping to another TB solves it. TB reset is a good Idea though. Good luck.

guysandiego

well, i got my car back from the dealer -- i got a new TB because i have a warranty but i will be throwing my old one back on ... Dealer doubts I got the ESP problem and limp mode because of the TB -- he thinks its because my alternator was putting out a whopping 7.2 volts !!! -- which can make everything go hay wire -- Anyways, i will not put the old TB on right away -- I want to make sure everything is running correctly 1st -- later i will swap it out and see.

jicl55

Well, one of the pins was not quite in, so it is working a lot better now. No ESP and no limp mode. The problem now is: Upon startup in park and warmup, it will sit at 1500 rpm and not drop down unless I throw it in gear. And I am getting CEL, I'll have to check the code right now, but I think last time was something like "higher rpm (or idle) than normal" or something to that effect......

jicl55

Started it up this morning after sitting all night. Engine started and warm up was normal. Went to 1200-1300 rpms, then dropped to 950. And driving was normal. Before it had been sputtering at idle, like a lack of fuel perhaps? CEL light was on: P0505 Idle Control Module and P0507 Idle Control Module RPM Higher than expected. Cleared the codes, started it up and in warmup mode got stuck at 1500 rpms again. Did throttle body reset then, and it began sputtering at idle like its trying to compensate for the extra air, but can't dump enough fuel possibly? Shouldn't be related to the codes I'm getting tho?

Haven't gotten it tuned yet, but didn't think tune would help with CEL codes or be able to adjust idle.

After I clear the codes, and at warm up in park, when it gets stuck at 1500 rpms, absolute throttle position is at 2-3%, which is what it should be with stock throttle body. I put it in gear, and throttle position eventually drops to 1% to .8% at 650rpm in drive.

Maybe leak somewhere now? Or is there a way to adjust the idle through STAR or programming? Weird.

skratch77

Im sorry to read this thread,but you are going threw the mess I just went threw.I gave up on my 82mm tb and went back to stock.

I wasnt having the drivability problems like you,just the tps was at .8-1.1 in gear and would eventually throw the 505codes and put the car in a limp mode.

my last resort before giving up was to bring the idle up with star,but never got around to doing it.I figured it would of throw the idle too high code that I got a few times also.

make sure your tb is not binding up on anything,I got the crazzy limp and all the t/c errors and the car went nuts when the tb ate my gasket and got the blade stuck in one position.

so maybe your tb has a spot where it binds up and is causing your idle problems.

just a heads up,hope it works out.

you can also try switching your tps sensor off the old tb to the new one and do a reset.

unplug tb
key in second position(wait 10 seconds)
key off
plug tb back in
key in second position for like 2 min(you will hear the blade moving back and forth as it calibrates)

jicl55

Your kidding. Not good news bud. I was thinking about adjusting idle or TB position through STAR, but didn't know if this was possible. I'll have to look into it. My idle is exactly like yours, even as low as .38% to 1.1%, but steady around .8%.

It throws P0505 and P0507 now. But it doesn't go into limp mode. Feels almost like it is sticking somewhere perhaps. I was driving slow, low rpm, no change in accelerator pedal position, and felt rpms drop slightly all of a sudden, then it starts sputtering at idle. But it will not go in limp mode now.

This morning, started and running great, but CEL light was on. No sputtering, smooth idle, etc. Just cleared the codes and started it back up and is started sputtering right away, getting stuck at 1500 in warm up, etc.

Seems like a calibration issue and the ECU is unable to compensate and is trying to dump mass fuel in. I'll check it again and try your TB reset procedure to see if it helps.

beauphus

if i ever get this stupid isle/sputtering issue fixed i will be able peacefully. most frustrating thing i have ever dealt with

guysandiego

too much air is getting past the TB flap at idle -- hints the high RPM -- and/or you have a vacuum leak somewhere -- I imagine its the extra air flowing through that 82mm TB --

jicl55

Went through all the same crap trying to adapt a 80mm from a CL600. Never worked. That's why I went back to stock, but thought I'd give the 82mm a try Before I had several problems: think throttle body was not compatible and I have a leak in the brake booster. Few more solutions I'll try before I give up tho.... Misery loves company, no?

jicl55

Couple of things left to do. Will try this weekend:

1. Run smoke through lines and see if there is a leak somewhere.

2. See if I can adjust/adapt TB in STAR somehow or adjust idle to TB position and compensate for higher revs.

jicl55

What kind of TB do you have on there MB 82?

jicl55

Tried this, saw TB flap move up (about 20% maybe) and close real quick then nothing. Didn't seem to help a whole bunch tho. I'll try again just in case.

skratch77

I messed with my 82mm tb for about 2 months,It never ran rough and the idle was smooth as silk.

Its not an air leak,I went to the point of pulling every line on the car and let the thing have the biggest air leak and it still idles fine.

the codes come from the ecu wanting to see 2.7 degrees at its set idle rpm,now your not going to get this with a 82mm tb because your letting more air in at the same blade angle,some cars are less prone to this and others like mine would throw the code in 5 min.

the car is in a limp mode when the code is thrown,I went from 460whp with cleared ecu to 413whp with the pending codes so its def doing something.

one way I was getting around the codes and limp mode was to put the car in N at every light and never let the car idle in drive.The second the car sees 550rpm and the tps at 1.1 it will flag the code.

here is my car not even a week ago taken apart for like the 3rd time trying to get it to work.I was running a 997 gt3 82mm tb with the wires switched around.









good luck bro,trust me I know how frustrating this can get.

I paid the dealer to reset the tb calibration and it didnt do anything.my last resort was to up the idle by like 40rpms but never got around to it.before messing with star I would get the car to run and drive like normal.My car drove like stock,perfect idle and smoth power band with the 82tb just threw the damn codes.So before taking it in make sure you get the car running right.

i got so frustrated that I turned my car back to stock lol

guysandiego

So basically the problem is known ---- due to the larger amount of air @ idle with the throttle blade @ ~3% -- the car will throw codes ---- So, is there any solutions to remedy these annoying codes and in some rare instances major limp mode ---- How are all these people running larger TB??? are they just content with that annoying check engine light? --- or are they able to get the super picky ecu to accept the larger TB?

lowprofile

I do not recommend this but I'm just providing food for thought. These throttle bodies learn what closed and WOT position are, there are no stops to adjust per say and no adjustments for TPS sensor.
With throttle body in hand, you can see that the throttle blade will close a little bit more if you push the blade. Once you remove the sensor cover plate, you can see where the non adjustable cam hits with the throttle in the closed position as well as WOT. The closed and open position can be altered, though not easily. You would be taking a shot in the dark, but you could reduce the closed position of the throttle, which in turn might get you up to the required % at idle.

Forrest Gump 9

Any update from this? I swap mine to the stock TB and eveything is fine (but what's the fun in that).

jicl55

Yeah, put mine back to stock. Not sure if it is something I did wrong, or install, or vacuum leak or TB itself or what. But if anyone is interested and wants to try it, PM me or email. Looking for $450, which is what I paid for it. Will also post in classified section. Thanks

guysandiego

are you going to include trhe adapter plate with the sale?