bhamg

I see via my diagnostic tool the following FT's:

STFT (B1) 3.1%
LTFT (B1) 7.0%

STFT (B2) 2.3%
LTFT (B2) 6.3%

Obviously the closer to zero the better but these readings are not outrageously out of line, correct? What are you guys seeing on your own cars?

roadtalontsi

you've definitely got a leak, probably intake gaskets. anything over 5% on long term will throw codes. You should be less than 1%, but you probably have a tune so that may change the "normal" for your car. anything over 1% on an mct car will cause the transmission to shudder badly, but your's is the old tq converter so you wont notice that.

bhamg

Thanks road...not exactly what I wanted to hear but good to know from someone who knows...much appreciated! If I drive it like this - e.g., I'm 46 miles from my M-B store - is it going to leave me stranded by the side of the road?

roadtalontsi

Normally the cars drive normally and almost unchanged other than the cel on. If thats the case it's ok to drive. If it runs like total crap and is unsafe than I'd get it towed.

bhamg

OK, thanks.

AwdthisC63

Quick check to see if intake is leaking is to spray some brake cleaning where intake meets heads. If engine stumbled the gaskets are at fault. M156 intake gaskets common repair. You should be ok to drive that many miles to dealer without break down on the road. Remember roadside assistance will tow your vehicle to mb dealer at no cost if your unsure if you want to drive vehicle.

Merc63

Roadtalon, can you explain the short and long term fuel trims?

If I remember mine are higher than that. I thought the percent was the correction factor from the base map? Short being instant feedback from o2s and long being an average over time?

bhamg

That's my understanding too. My LT's were taken over a duration of 4,600 seconds and recorded trims are positive percentages on the fuel side.

bhamg

Good to know, thanks.

abcut973

Yes the trims are percentage of correction. LT's have to be the lowest as possible. 6-7% in your case indicates you have a leak somewhere.

jptaylor

The brake cleaner will be MESSY and can discolor aluminum and plastics...the best option is a butane/propane torch (think of the green Coleman camping stove bottles)...grab one from WalMart for $10 and a 3' piece of 3/8" hose and you can now cleanly get to anyplace you want on the engine (top, bottom, front and firewall)....make sure you buy the torch kit as it comes with a screw on brass torch with 3/8" tip AND A VALVE!!!! When you pass a leak with the hose engine rpm will shoot up noticeably

PetroC63

Your tune is rich. Positive fuel trims are adding fuel. Normal for a one size fits all tune.

bbb_fatboy

I really enjoy reading these posts where people dig into the complexities of our cars.
Does getting this level of data/information require a Star C4 tool, or do other diagnostic pkgs also work?

Jasonoff

The O2 would be sensing a lean condition if the ECU needs to add fuel to correct the AFR.

Merc63

I believe there is a base map (tune) with injector pulse widths, also another map with target lamba values. The fuel trim percents are the difference between the base map and the target lamba values, it's the correction factor plus or minus fuel.

It may be a bit more complicated than that, but that is the jist of it I think.

bhamg

Relatively inexpensive scan tools/code readers can do the job, although the cheap Amazon handheld types frequently don't work with German cars. Bluetooth versions are popular here. IMO the minimum level of functionality you should look for in addition to determining codes and emissions testing readiness is live-data streaming display.

Merc63

I have a $50 scanner that hooks up to my laptop and will do a full odb2 read out.

Gerry_M

Which scanner do you have?

I started modifying cars way back using my 97 M3 and its suoerchared now. The old late 90's decade AutoEnginuity wont talk to my 09 C63.

I found that STFT and LTFT are usually a high +/- numbers due to the differences in added hardware and tunes. The trim gets you the proper fuel for your mods that a basic tune did not fully account for.

bhamg

Great...heading there later today!

str8six

Let us know how your leak test goes, but I believe your LTFT's are within acceptable limits. Most sources say +/- 10% is acceptable.

I've been monitoring my fuel trims for a while now and with the 10% ethanol gas here in Colorado, my LTFT's hover around +11%. . Occasionally I will run the E30 tune that Jeremy sent me using E85 mixed with 91 octane to bring ethanol content to 30%. When running E30, my LTFTs will get near 25%. I can watch them gradually drop back down to around 11 or 12% as I start adding 91 back in and go back to the regular tune. Although ethanol has a much higher octane rating than gas, cars require 30% more ethanol to produce the same energy.

Even with 25% LTFT's on the E30 tune, I get no CEL's or codes and the car runs strong. The nearest place that sells ethanol free gas is about 2 hours away, so I haven't had chance to see what effect pure gas will have on my trims.

If you have an android/ios device you can buy OBDII Bluetooth or wifi adapter and download the Torque app for $10. With the app, you can view all the parameters of your car, in real time, data log the PID's of your choice, and view/clear fault codes right from your phone.

I bought this adapter from amazon for $24 and it works perfectly

Merc63

Not sure the name but it's just a cheap scanner I found online.

roadtalontsi

long term is like a global change in the map for adjustment. So its adding 6-7% of fuel everywhere. The short terms are more of an immediate quick adjustment that usually kind of bounce around that it is adding on top of the long terms but the short terms are only going to be that much for that specific rpm/load condition. I dont even think the sds lets you read short term fuel trim. It has the long term fuel trim for idle speed, part load and high load. anything over 5% will turn the check engine light on. I'll see if i have time and get a picture.

Merc63

5% in stock form right?

Tuners must be increasing this tolerance?

str8six

Both the dealer and Kleemann told me trims need to be at least in the 20's to get a CEL

PetroC63

Are these readings while cruising, part throttle or wot?