DonnieD

I am writing this article as a continuation of the thread about the EC tune and 550 injectors coupled with an 82 mm throttle-body causing erratic idol and running conditions.

The engine runs perfectly most of the time however it does run erratically after a long run at extremely light throttle and then trying to re-accelerate. When this occurs the engine runs extremely Lean to the point it will backfire buck and pop. At times when pulling up to a red light at idle it will do the same thing.

At first I thought this was a result of the 550 injectors causing a rich overall mixture and the computer compensating for it. So i reinstalled the stock injectors and has Jerry from eurocharged send me a new tune. It displayed the exact same drivability issues.

I then contacted other industry pros to help out. One led me down the path of the throttle body and gave me a good argument. Since NO 112-113 engine ever came with an 82mm TB, the calibration just isn't there. I think this is very well the case.

I took apart a stock TB and an 82 to measure a few things. Here is what i found!

The gear set and stepper motors are identical in every way. The sweepers are slightly different in the resistance value. I am going to try a set of resistors to get an identical setup to stock to see if that is the problem. Ill let u guys know.

shardul

iTrader: (1)

Good info
What if you swap the caps of the tb?

Shifter

Good info. These issues are why I'm sticking to a 80 mm

adianaty

Did you happen to check resistance at full open to see how it scales. I'm wondering if this difference is an offset and if so "allowed" as a result of the TB cal the ecu does.

E55Greasemonkey

Thanks for posting. LOL I put an inline fuse in my meter as well, tired of buying those expensive fluke fuses...

Anyhow, looking at the pics the boards look identical, at least from this side. I wonder if swapping them like Shardul said would cure the problem. Did you compare your readings to the one installed in your car, to make sure both 82's read the same?

Another thought, was the car ever dyno tuned? Or just a canned tune? My canned tune was lean and once on the dyno it was richened up and the car ran much better. Since not everyone has this issue with the 82, I'm wondering if a slightly richer tune would compensate for your problem. Maybe Jerry can richen you up a bit from where it's at now to test. Is your fuel filter, and pumps, and pump connections all in good condition?

DonnieD

You cant swap the caps from what i can tell. The little sweeper arms are fine as frogs hair and are fragile. I think once opened, it is junk! I think the 80 mm is the cure, but will experiment with the resistance before swapping again an spending another 1,000 on a throttle body!

The saga continues.

Manuyc

Nice

Forrest Gump 9

The caps are swappable. I've done it many time before.

black06c230

Sorry to hear you have so many problems with your 82 but wonder why your car is being so difficult. Many run a 82 as do I and don't have that many problems. Mine runs just fine now but at one point it do the same as yours. Not that it will help but I would get the crazy idle after driving like you mentioned and once my tune was reflashed to turn off the cats and adj the tq limiter it went away. Last 6 months or so have been perfect.

Shifter

Here is kleemanns setup, they use 80mm and a m275 tb

RaFFi ///AMG

So is it best to just go with an 80mm? Sacrificing some performance gains for better drive-ability?

AgSilver

You can add the equivalent of approximately 2mm by machining the TB shaft.

PACougar

Considering how many people have 82mm TB's, I think this is a problem the OP is having vs a problem that 82mm TB's have.

black06c230

Agreed I don't have any issues like this with my 82 now for the last 6 months and drives and idles just fine.

Denroll

It seems hit or miss. I had this problem really bad and then found a vac leak. Fixed the leak and thought I had cured the problem. It still does it, but on a much smaller scale. The only way I can tell now is to watch my STFT%. At a certain point in my daily commute, it happens like clockwork if I am light on the throttle.

If OP can fix this, I will force someone to give him a beej, like this.

Tech-Tune

On other TB's or these 2 in particular?

bstudey01

I know of four or five on this forum, me included, that have the exact same issue, so there has to be something to it.

SavMan

I have had 3 different 82mm TB, had it fitted by 3 different people. Last one I did myself each time all new gaskets including the large O ring on the lower TB and the car has been tuned by 3 different companies so its not the tune. Map sensor voltage changed, TB angle is now at 2.5% at idle and both in gear and park idle set to maximum.

I still get the code but just learned to live with it, I now set an alarm on my data logger so if STFT% exceeds 15% on light throttle position it flags up and I can reset when safe.

Its not a leak issue the fact that it can be replicated the same as others, light throttle slightly increased load i.e. uphill typically around 80mph and then engine stutters and B28 Pressure Sensor Signal Implausible.

I had wondered if it was year related and that certain ECU's produced on earlier models had slightly tighter parameters but that does not seem to be the case. I have seen 03, 04 and 05 models post the same issue.

I may well pull the end cap of my original 74mm and stick it on one of the 82mm sitting in the garage.

SavMan

Here's a link to the thread I posted earlier this year

https://mbworld.org/forums/w211-amg/...-problems.html

bstudey01

I just brought my car into Speedriven today to see if Marcin could figure it out. He decided to add a little fuel in the tune in the 1900-2400 rpm range, which is where my issue occurs. I drove the car back from there about 70 miles on the highway with my fingers crossed watching the dashdaq and AFR's the whole way home. I played with the throttle from cruising at 60, 65, 70, 75, 80mph with no throttle then light appllication of throttle, up hills, down hills, around corners and could not get it to replicate the issue that had just happened on the way to his shop in the morning. I'm not positive that it is fixed but have my fingers crossed I will keep you guys updated.

Denroll

Mine's an '06, so we have all the years covered, lol. And it's the uphill at 80 that gets me every day.

black06c230

Something is certainly up. Like I said I don't have any issues And seeing you all can have issues just cruising at 80 and going up a hill is really odd. I always cruise at 80 on the interstate and its hilly here in Alabama and I never run in to that.

Bstudey I hope that adding fuel helps you out. Certainly keep everyone posted.

bstudey01

I spoke too soon. Just took the car out to find some hills and bamm!! Actually was only doing about 65 going up the hill and felt the slight hiccup stft's maxed. I knew it was too good to be true. Question for others that are having this exact issue, do you guys also get a hiccup once and a while at lower speeds upon light throttle application. I do notice it sometimes around town at about 30 when I press lightly on the gas. No, it is not the s/c engaging and it feels almost identical to the one on the highway but it doesn't cause the stfts to go out of whack or throw the code. Just thinking out loud. Anybody swap the cap from a 74 to theirs yet? I may try this, seems like it shouldn't be too difficult

Denroll

I'm thinking about going to a 90, lol.

bstudey01

Who else having this issue has their cats deleted? Do you have a code for catalytic below threshold?