Shadedmoon

Hi, I've got a bad issue with the newly acquired C200 Kompressor model year 2000.

Low end power (stop lights, from standstill) is terrible. If I give anything more than a hair of throttle, the car does nothing for a while, then jerks and jack rabbits a while. Upon reaching RPM over say 1500-2000, and on gear 3,4,5,6 she runs smooth like it should.

Bad O2, MAF? Other sensor or gremlins?

What I've checked so far

- New air filter, didn't solve it
- Fixed a vacuum leak, didn't solve it

I cleared the fault codes of the engine and drove around a bit. No error code reappeared.

When the car is cold, just starting it and driving away the first minute, the power at low end seems OK. Much better than warm anyway.

The Torque Light app mentioned there was a fault in the feedback of the O2-sensor.

Inputs are very welcome. Fuel consumption seems OK:ish. Slight smell from exhaust. So fuel mixture is very likely not perfect.

RedGray

Which is it?

Also, what is your long term trim?
Post a screen-shot of graphs of the long term trim, main 02, rpm, MAF.

Shadedmoon

Thanks for the answer. I'll have a look.

RedGray

Something similar to the screen captures below:

Shadedmoon

I was able to write down a few data from a torque.

At idle and fully warm engine.

Maf 4.5 g/s
Idle 740 rpm/s cirka
O2 sensor 1 and 2 both cirkled between 0.1-0.8 volts

After driving some more I got the CEL and code P0170. Fuel trim adjustment outside of spec.

I think the maf may be aftermarket. So will check that during the week.

I also found a vacuum hose with a yellow end which is not connected to anything. Standing in front of the engine it is located to the left of the center of the car. Quite close to the front. Should that be or where should it be connected to?

Maf 4.5

Shadedmoon

Timing advance cirkled between -10 and 0.
16.6 inch/hg was the intake vacuum at idle.
Fuel trim one bank one 1x1=-40. All other fuel trims were at -30 so figured they were not used.

Sorry no graphs and actual photo. Hope it is possible to draw conclusions anyway.

RedGray

What was the long term percentage?


Take a picture of the vacuum line. On the left/passenger-side, iirc, there's a vacuum line that goes to the ?"EGR" bypass? valve that is on the front left of the engine. Iirc, that valve actually controls if fresh air (from the baffle) is sent into the exhaust during startup - to reduce cold start emissions.

Shadedmoon

It is probably -40%, despite how big that number looks. Unless possible to change scale in Torque.

OK, yeah the car could have had an EGR-delete. I'll snap a photo during the week. Only prob. is the hood isn't openable right now, so a workshop will take a look.

RedGray

I doubt that it's 40 percent. Iirc, the max is ~+/- 15%-20%.
So, that may be the raw value?

The engine should be around +/- 0-4%. Imho, anything over 10% is often bad.

I'd say between 5% and 10% is maybe okay - but there may also be a problem.

If there are engine mods, then the engine may likely be +5% to +10%. The long-term trim would likely be higher at high loads and higher rpm.

The long-term trim is likely either a 2-dimensional or 3-dimensional table based on rpm, load, etc. I don't know what MB uses for either the MB M111 or M271 engines.

Shadedmoon

OK thanks.

Well, the last data point frozen in the app is showing -16.4%, I'll verify with the car at idle again. Let's hope it actually isn't that high.

Glyn M Ruck

What is your fuel consumption like? Not sure what OK ish means, Any change? Remember that it is critical that your temperature sensor is good. Seems your car is OK in open loop mixture enriched but not warmed up closed loop with the MAF in circuit. It is critical that the ECU is fed the correct engine temperature for proper fuel trim. It is also critical that the MAF is sound.

Shadedmoon

Thanks for the reply Glyn. I've ordered a new Bosch maf yesterday. The one in the engine bay looked suspicious from day 1. The arrow on the intake tube and the maf point towards each other. That can't be correct. Also it ks like an aftermarket unit. I've replaced a couple of mafs in other cars before.

I also had the same thoughtime open loop is ok but not closed. Which temp sensor do you have in mind? Intake air or coolant?

insame1

what is the intake air temp?

Glyn M Ruck

NOT IAT! The coolant temperature sensor that feeds your gauge also feeds the ECU. You might have ended up with a VW/Audi MAF. They look the same but won't work on a Benz.

insame1

WHY NOT? If the IAT is too high the SC will shut off. Ask me how i know.