Ian M2

Hey Guys Long time Lurker here, but this time it seems I have a combination of symptoms not resolved by forum posts of others yet, so here I am.

So, the car in question is a 2001 C320 with over 100k miles, I've owned it for 3 or so years, but for the last year it's not seen much love.



Back when I first acquired the car, she had a Misfire when flooring the car, always popped up on Cyl 6. As well as an intermittent rough idle still not resolved to this day. Replaced that coil pack about a year ago, still didn't fix that issue.

Fast forward to last winter when the old battery went flat on me, taking out the Emissions stuff before the car needed a Vermont State inspection. Which I add, they've recently switched to having to have all readiness flags needed to pass (ugh).

So during that time, the car devolved a nasty hesitation, bordering on a full stall on takeoff. Well, I tried cleaning the MAF, both in the hopes of clearing this problem, and that old rough idle. No Dice, still rough as hell, still choking.

Tried unplugging the MAF to see if it would improve performance. NOPE, even worse! (Used CRC MAF cleaner)

Changed the Fuel filter to the same end. Nope Nothing. Although it didn't look great inside, almost.... sooty looking (yes, in a fuel filter).

Dropped a Can of HEET into the tank thinking maybe an ice blockage of some sort, I swear it improved for a bit, then died out hard to say.

So in all this process, if pushed just a little too hard, codes for random multiple misfires, varying cylinder numbers misfiring, and a bank too lean code were recurrent. Also, following the Drive cycle for the car would pass everything BUT the one tied to the MAF, which one that is, is in my notes somewhere. Strangely, to set that flag, if I unplugged the MAF, started the car, turned it off, and then restarted. Boom, Flag Set.

Finally managed to squeak the car through inspections. Almost a month late. (Imagine trying to test drive this car with a bad inspection sticker, and an overzealous local PD...).

Kept occasionally testing, same results all the time.

About 2 weeks ago, got a fuel pressure tester. Had to jump the car. Tested it at idle, under revs, and key on, not started. 53 for key on, 55-57 I think for revs, and about the same for idle. Managed to make the car stumble while recording fuel pressure values via camera. Nothing, the stumble is NOT related to fuel pressure.

Next stop, cleaning the MAF again, thinking maybe I’d missed last time, and guess what. For about 3 days, the car ran pretty good. (I also reset the throttle adaptation in this time) Tried hammering the accelerator a few times. No stumbles, no Misfires, Nothing. Pull MAF wires, Car runs like crap.

Thinking I’ve got it, I go to test the ESP yesterday (another problem) and the stumbles are back with a vengeance. Not only does it stumble from takeoff, but now it can hardly pull itself up a hill! And occasionally when pulling to a stop, will lurch. Get above 2000 rpms though and suddenly some of the power re appears (I had to drive it home in 3rd gear Max). Interestingly, no engine codes were thrown, even with having to pedal the gas to not get stuck in an intersection.



Tested for a vacuum leak. Left the air box on the engine and sprayed starting fluid all around the seals and hoses near the MAF. Nothing. Guess that’s not it.

Sprayed some starting fluid into the air scoop while monitoring revs. Drops from 800 idle to south of 600. (Think I Bottomed at 450 once), also feels like it's going to stall right there, then recovers.

Tried cleaning the MAF again, on the off chance it would help. Nope, no dice.

Tried looking at the Throttle body, everything looks nice and clean as best I can tell with a camera.



Now, after a little searching, some of these numbers seem a little out of whack

All are at idle

Rpm between 700 and 800

Long term fuel trim Bank 1 28.9% (closer to 0 is better?)

Long term Fuel trim bank 2 28.1%?

MAP about 38 kPa

Spark advance between 0 and -17.5 degrees with spikes near -30

MAF 4.55 g/s or so. @ 674 Rpm



In any case, some of the thoughts in my head right now are:

Can I swap the MAF from my 07 C280 4Matic for testing purposes? Part numbers appear to be wildly different (and prices)

Injector cleaner? Would that do anything right now?

Why is it that adding some starting fluid makes the revs drop like mad? Seems like the car would have to be running rich already for this to happen. (AFAIK I did not spray an excessive amount) I was under the impression that testing with starting fluid would result in a spike in revs, not a drop.

Would having the long term fuel trim reset by the battery going flat / throttle body adaptation cause the short period of the car performing well? Or is this just some sort of weird coincidence.

Why am I not seeing codes for this fuel trim if it is indeed way out of spec, and why is it so out of spec?



Any thoughts would be most welcome. This poor car is just collecting dust and rust while I try to figure this out.

Thanks
Ian

Ian M2

Ok. To amend my previous post. First off I found 11 Separate Codes in the ME2 motor electronics (I have an Icarsoft MBII) Half of them have no entry in its database.
P2016-002 Right bank too lean essentially
P2016-016
P2016-064
P2017-001 Right bank too Rich at idle
P2017-016
P2017-064
P2085-002 Left bank too lean at part load
P2085-016
P2086-001 Left Bank too rich at idle
P2086-016
P2086-064

I reset these codes, restarted the engine and gave it a few revs, no codes re appeared, i presume this is related to my earlier testing with starting fluid.

However, the real good one for the day is. I decided to reset the ECTS using my MBII, Long term fuel trims reset to 0%, and this bad hesitation seems to be gone for now (the slightly shaky idle remains). That being said, last time I reset this (using the pedal to the floor reset, not my scan tool) the problem re-appeared after a while. Heres hoping i've got this one down.

fuzzysi

I've got something similarish on my 2005 C200K.

Failing the emissions because fuel trims are too high.

Updating the ECU at MB fixed it momentarily, but still the fuel trims creep back up such that it fails.

Mechanically all is good. No vacuum leak.

Current best (worst) guess is catalyst not working so second O2 sensor calling for more fuel to get it up to temp, but it doesnt because its dead.

Ian M2

I’ll have to do a little testing to see if resetting the adaptive throttle can clear fuel trims. I know that the Icarsoft can do it through the ETCS reset function. And that seemed to fix it. My fuel trims are actually below 0 for the moment. (Only a couple percent. Might have misread anyways)

out of curiosity, what’s the voltage on your post Cat O2 sensors? Mine are somewhere around 0.717 Volts and steady. The pre bounces like a kid on a trampoline (which to my understanding is expected)

fuzzysi

On one data grab i have it seems to be around 0.37 to 0.42 volts, but then a second is 0.48 to 0.52 volts

Ian M2

Looks like I need to retake those values after a drive. Been hard to take the car out until recently. (Doesn’t help I live up a gravel hill. And have a hill on the road as well. So power loss means I get trapped)

according to this general article
http://www.autotap.com/techlibrary/u...en_sensors.asp
it looks like your sensors are in the expected range. I’ll see what mine come back as at idle and after a drive to compare.