M113K cold start rough idle

[Matt58]

Thanks for

They all have a slightly grumbly idle when cold. If yours is particularly bad, I would start with looking at the adaption values. These will give you an indication on too much fuel, or too lean at idle and what its doing to compensate. Air leaks are common and adaption values will tell you this (STFT and LTFT on OBD readers)

Thanks for reply, I’ve got icarsoft and have looked at values, but I’m still learning, and by no means proficient. I’ll look again and document when cold and fully warmed up. I didn’t think they were to far off when I last looked, but if I post them next week would you be kind enough to give me second opinion. I suppose on initial start up the mixture is super rich, this is the period were motor runs absolutely rock solid, I’ve changed all fuel injectors with stock ones and still have secondary cats and I would think original O2 sensors. Is it the case that you don’t get true long term trims until the motor is hot? Sorry for all questions, but although motor has never been bad as to cut out, I do think it could be a little smother. Thanks in advance, Matt.

 

[Matt58]

Thanks for

Thanks for reply, I’ve got icarsoft and have looked at values, but I’m still learning, and by no means proficient. I’ll look again and document when cold and fully warmed up. I didn’t think they were to far off when I last looked, but if I post them next week would you be kind enough to give me second opinion. I suppose on initial start up the mixture is super rich, this is the period were motor runs absolutely rock solid, I’ve changed all fuel injectors with stock ones and still have secondary cats and I would think original O2 sensors. Is it the case that you don’t get true long term trims until the motor is hot? Sorry for all questions, but although motor has never been bad as to cut out, I do think it could be a little smother. Thanks in advance, Matt.

Sorry, one more question (promise) how important is the rubber pipe on the base of the throttle body, I do remember it not being in the best shape when I was doing injectors?

 

[alexanderfoti]

Short term trims operate on top of the long term trims.

Trims only update when in closed loop, so typically take 2-3 minutes to start updating.

If you start up the car, and the trims go to -15% and stay there for a while, the car is removing fuel as its sensing too little O2 in the exhaust stream.

As you had oil burning issues, its quite likely the o2 sensors are fouled and are lazy.

The hunting idle is more likely to do with an air leak or throttle body fault. Both will show up as + short term fuel trims , which will eventually end up in positive long term fuel trims. The long term trims are the ones you want to post up as they paint an overall picture. The short term trims are only showing a snapshot in time

 

[alexanderfoti]

Sorry, one more question (promise) how important is the rubber pipe on the base of the throttle body, I do remember it not being in the best shape when I was doing injectors?

This is usually the most common source of issues like this, so I would look there first

 

[Matt58]

Short term trims operate on top of the long term trims.

Trims only update when in closed loop, so typically take 2-3 minutes to start updating.

If you start up the car, and the trims go to -15% and stay there for a while, the car is removing fuel as its sensing too little O2 in the exhaust stream.

As you had oil burning issues, its quite likely the o2 sensors are fouled and are lazy.

The hunting idle is more likely to do with an air leak or throttle body fault. Both will show up as + short term fuel trims , which will eventually end up in positive long term fuel trims. The long term trims are the ones you want to post up as they paint an overall picture. The short term trims are only showing a snapshot in time

thanks so much for explaining that to me, I’ll do some digging next week, and recheck throttle body pipe.

 

[Matt58]

Short term trims operate on top of the long term trims.

Trims only update when in closed loop, so typically take 2-3 minutes to start updating.

If you start up the car, and the trims go to -15% and stay there for a while, the car is removing fuel as its sensing too little O2 in the exhaust stream.

As you had oil burning issues, its quite likely the o2 sensors are fouled and are lazy.

The hunting idle is more likely to do with an air leak or throttle body fault. Both will show up as + short term fuel trims , which will eventually end up in positive long term fuel trims. The long term trims are the ones you want to post up as they paint an overall picture. The short term trims are only showing a snapshot in time

Just found some screenshots I took a while back.
STFT L&R constantly fluctuate between 80-850 MV (would that be millivolts?)

LTFT R 02 sensor after TWC (KAT) 692MV
LTFT L 731MV
Not to sure if this was on cold or warm engine so will do more next week. Thanks again.

 

[alexanderfoti]

You need the fuel trims (in %), you are reading the O2 sensor voltages which are not useful.

0% means car is not making any changes to the base map based on sensors
+% means its adding fuel
-% means its removing fuel

The O2 sensors will always switch lean-rich-lean-rich, as they are "narrow-band". The ECU averages the amount of time they spend rich/lean to adjust the mixture around the ideal point.

After CAT o2 sensors are not helpful for mixture control, they should always read low(er) voltages when the CAT's are up to temp and stay there.
Pre CAT O2 sensors will zig/zag when plotted, for reasons above

 

[Matt58]

You need the fuel trims (in %), you are reading the O2 sensor voltages which are not useful.

0% means car is not making any changes to the base map based on sensors
+% means its adding fuel
-% means its removing fuel

The O2 sensors will always switch lean-rich-lean-rich, as they are "narrow-band". The ECU averages the amount of time they spend rich/lean to adjust the mixture around the ideal point.

After CAT o2 sensors are not helpful for mixture control, they should always read low(er) voltages when the CAT's are up to temp and stay there.
Pre CAT O2 sensors will zig/zag when plotted, for reasons above

Yes I see, thanks for explanation, I’ll look at % on tues when I’m next using car, like I said I’m still on a steep learning curve with this, thanks for your patience.

 

[Matt58]

You need the fuel trims (in %), you are reading the O2 sensor voltages which are not useful.

0% means car is not making any changes to the base map based on sensors
+% means its adding fuel
-% means its removing fuel

The O2 sensors will always switch lean-rich-lean-rich, as they are "narrow-band". The ECU averages the amount of time they spend rich/lean to adjust the mixture around the ideal point.

After CAT o2 sensors are not helpful for mixture control, they should always read low(er) voltages when the CAT's are up to temp and stay there.
Pre CAT O2 sensors will zig/zag when plotted, for reasons above

Just found some data that I videoed that I think is what you asked for.
STFT B1 0.0/-2.3%
STFT B2 0.0/-1.6%
LTFT B1 -1.6
LTFT B2 -2.3
Intake manifold absolute pressure 32KPA
I’ve only mentioned MAP as I haven’t a clue what it’s meant to be, and I thought I would replace whilst the surge tanks were off, but I was unsuccessful and managed to create a major oil leak from dip stick grommet, so decided to call it a day after repositioning grommet and luckily steaming flow of oil.

 

[Carlos2k]

Mine hunts a little on idle, more cold than hot but its never overly bothered me and i have seen multiple people report this with the m113k. Will watch this thread and see what comes of it.

 

[Dashi111]

Hi there, my 2003 E55 with 108k does exactly the same minus the ticking, I like you have in the last 18 months changed plugs leads coil packs, injectors surge tank and throttle body gaskets. On initial startup winter or summer fast idle choke is rock solid, but when Revs decrease the engine never seams that happy, more consistent once drive is selected, and solid again after a few miles, I’m frustrated by this but learned to live with it, no codes by the way, no smoke on start up, nothing when accelerating hard and on deceleration, but I’m using around 1.5-2 lts of 5w40 liqui moly in between 5k mile services, which is a mystery to me, but I’m monitoring this very closely, and when I changed plugs they were all in good condition.

I am in the EXACT same situation as you. Fast idle solid, low idle poor, worse in P than D. Same oil consumption, same recent maintenance, 109k. lmk if you ever get to the bottom if it.

 

[Matt58]

Yes I’ll certainly keep you posted, going to do some more work on her in the summer. I still think it might be something to do with the secondary air valves, maybe one is getting lazy. I do remember Tasos on YouTube raising idle to help smooth things out, but my icarsoft isn’t capable of doing that, in the mean time I’ll change some of the old rubber hoses (pcv etc) and keep hunting for vac leaks.

 

[SnowBear57]

Hi,

I wanted to ask if other M113K owners, see their car engine stumble and possibly misfire on cold start?

Mines has been doing this for a while now, despite having new
- Plugs
- Leads
- Coil packs
- New Injectors

within the last years/4,000 miles. Its also been 4,000 miles since it had a full rebuild.

Once warmed up, the idle hunts 100+/- rpms in Drive or reverse only. The hunting started after getting a stage 1+ remap from MSL. Went back there twice and they can't find anything wrong with the map so. They checked spark plugs to see if they are seated well, map sensor and throttle body changed too with used but working units.

Any suggestions on this please?

Bear in mind that no codes are being thrown up, this was confirmed by merc specialist rather then my own conduct.

I recorded a video this morning of it on cold start, you can hear a ticking noise which is coming from under the rocker cover which goes once I blip the throttle a bit and once warmed up. If you hear the oil pump whine, you can hear it somewhat misfiring and about to cut of for that second.

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Wow it is a bit rattley and you can definately hear it miss then it seems to recover

 

[alexanderfoti]

Put it back to stock and see if it goes away. If it does, pursue this, if not it rules that out.

The mapping shouldn't be touching anything around the idle area.

 

[SL03WLY]

Yeah unfortunately its still exists today. Had fuel filters and air filters replaced in the last week. Though it picks up much better that fluctuating idle is still there. I did notice when I was going into the Mercedes Narnia with DAS Xentry C3, I recorded all the settings in the ECU and noticed the Post-O2 sensors are off. Not sure if that'll make a difference but will one day when I can be bothered to, turn it back on to see if a difference can be seen or not so. I mean the amount of parts that have been changed and yet still persists.

 

[alexanderfoti]

Yeah unfortunately its still exists today. Had fuel filters and air filters replaced in the last week. Though it picks up much better that fluctuating idle is still there. I did notice when I was going into the Mercedes Narnia with DAS Xentry C3, I recorded all the settings in the ECU and noticed the Post-O2 sensors are off. Not sure if that'll make a difference but will one day when I can be bothered to, turn it back on to see if a difference can be seen or not so. I mean the amount of parts that have been changed and yet still persists.

Secondary o2s are not used for fuelling adjustments on these and are only there to check function of the cats

 

[joe2612]

I had a recurrent vacuum leak years ago that was nigh on impossible to find. I ended up making a DIY smoke tester out of a tyre pump, glass jar, soldering iron and a cloth soaked in baby oil - worked a treat!

 

[SL03WLY]

I had a recurrent vacuum leak years ago that was nigh on impossible to find. I ended up making a DIY smoke tester out of a tyre pump, glass jar, soldering iron and a cloth soaked in baby oil - worked a treat!

Nice, and where did you find the leak then using this kit?

 

[joe2612]

I’ll try and remember , it was about 6 years ago but I think it was a poor gasket seal. It was a permanent slightly rough idle in my case however.

 

[SL03WLY]

Right, so an update (Though may be speaking too soon). After BOTG and meeting and seeing (IIRC) Haydens E55 where he was advised his crank pulley needs changing. I compared his one to mines and mines was far worse. After PCS changed this over for me the idle was a lot smoother and no more surging. I just done a cold start now (26C ambient ) it's not doing that "about to cut off" business now. Though will have to see how it is over the next few weeks.

Does this sound right to others. Would a worn out Crank Pulley cause something like this?