drtyjrzy

for a few weeks I noticed if I left my ac on when I got home, the next morning the motor would sputter and almost stall when I started it. no big deal, I'll make sure to turn off the ac when I get home. but yesterday I was sitting at a light, an hour into driving, and turned the ac on and got the same reaction from the motor. other than being embarrassed to have my Mercedes sound like a 81 corolla it's not a huge problem right now, but if this is a sign of a bigger issue I would like to address it now. anyone else have these symptoms?

AnswerSS

I had the same issue on start-up every now and again. From what I could tell, there is no pattern for when or why it happens, but it sounds about the same. It starts and hesistates, sputters and dies. It only ever happens the first try though, since it always starts up fine on the second try and continues to work as it should.

I'd be interested if someone knew what this could be.

drtyjrzy

mine has never actually stalled. it seems at though it's going to, but kicks in right before. I was more or less wondering if there is an easy fix and/or if it is a sign of things to come.

Russell Ormerod

Possibly your ac compresser busy seizing. eventually the shaft will shear and you will have no AC,

drtyjrzy

ok, dark cloud, you must be the same guy that makes sure people know their cold sore is herpes. lol jk. should I fix it now or wait until it goes completely?

pcy

if the compressor is indeed seizing, you don't want to wait until it seizes completely. It will shred the belt (at minimum) and may damage other components along with it.

If this option is available, buy a shorter belt to bypass the compressor until you fix the issue.

AnswerSS

Does the compressor turn on even if the climate control is turned off and the AC Off button is selected? Mine is always turned off when I start the car.

drtyjrzy

I have been using the auto temp function with the ac on. if I leave it on when I I turn the car off it is on again when I start up. but if if I turn it off before I turn off it remains off. is that what you were asking?

Glyn M Ruck

Remember Benz uses a swash plate compressor. It has no clutch. It runs all the time. It only starts pumping as you change the swash plate angle via it's actuator. The swash plate is supposed to be at neutral position on startup.

Does the Poly V belt protest when you "turn on" the A/C?

Engine stumble can be caused by the upstream O2 sensor cycling too slowly. But then it should do this independently of the A/C.

drtyjrzy

first of all I want to thank you glyn for all of your posts. I have learned quite a bit about my car in the past two months from you. if I start the car and have left the ac on, the ac will not come on until the rpm's have settled back to normal idle (basically enough time for me to turn off quickly if I notice it's on). but then when kicking in would drop the rpm's to 4-500 and make the sputtering sound almost like if you had the choke pushed on a small combustion motor. when it only happened upon start up I wasn't concerned, I would wait a min or two until I got moving to turn it on. but when I turned it on the other day at operating temp at a red light and did it again I got concerned. i know that other cars will momentarily raise the idle level when ac is turned on to compensate for the extra load and it seemed like that is what was not happening, but you are saying the compressor runs all the time so idk if that is the case. how do I determine if my o2 sensor is bad and where is it located?

Glyn M Ruck

If the O2 sensors are bad you should be storing codes - but do not always do until they are chronic. Check for stored codes with an OBDII scanner. Places like Autozone will read for you if you don't have a scanner.

Is your car MT or automatic? If you load the engine through other than the A/C, e.g. putting the car in drive does it stumble & splutter?

What mileage has the vehicle done. What is the general condition of tune. e.g. spark plugs?

Glyn M Ruck

Here is the upstream O2 sensor above the Cat. But before you go changing things lets read the codes. I want to know whether you are storing misfire codes etc. Let's not waste money on parts before diagnosis.

Please do an HVAC controller reset just to make sure that we have that at default.

https://mbworld.org/forums/c-class-w...tic+easter+egg

drtyjrzy

manual trans. it has 75000 miles. I just bought it at 71800 so I'm not sure about what maintenance has been done. I am not storing any codes. I know this because I just fixed a vacuum leak ( on the dealers tab thank god) and that was the only code I had. p0456 I think. and no I can't recreate the symptom by doing anything else. I'll try the hvac reset when I get in the car after work.

drtyjrzy

I did the hvac reset. seems to have worked but didn't change the sputtering.

LILBENZ230

My car has never done this at start-up, but has done it here and there the entire 3 years and 90,000 miles I have owned it - albeit, only at low speeds like rolling through a parking lot and coming to a stop, quick sputter/feels like it will stall, then recovers and is fine. It was doing it at 25k miles, and it will still sometimes do it at 114k miles. It's never actually stalled, though.

If you leave the A/C off, it doesn't do it at all? I was also under the impression that the A/C compressor seizing up won't disable the car, shred belts, or anything.

Glyn M Ruck

Suggest you remove the Poly V belt & see if the sputter is still there. Don't run for too long or you will overheat the engine.

This will tell us if the problem is mechanical or electronic.

drtyjrzy

ok. it's a holiday weekend so I don't think I'll get to it just yet but I will try it this week and let you know how it goes.

Silver C

I never realized the A/C has anything to do with engine sputter/stalling. Hmm... Interesting.

drtyjrzy

ok glyn I hope you are still watching, I never did the test run without the belt because the problem got way more intermittent. I figured I would wait until I was sure that it would do it again before I tried. but then today while coming to a stop and using the a/c I heard a pop/click noise and now I only blow hot air. I am now assuming that I am low on refrigerant and the system has turned itself off and I was prob teetering on the edge of low pressure before and that is why my compressor was straining the motor. does this seem logical? if so I would guess that I just need to get the system recharged.

Glyn M Ruck

Get the system recharged properly to the correct pressure. You can't diagnose anything on the a/c system without full pressure.

I don't think this was straining the motor but could have been confusing the high idle circuit.

This will also tell you if the compressor is sound.

drtyjrzy

the system has 100 psi. is that what I'm lookin for?

drtyjrzy

correction. 95psi low side. 125 high side

drtyjrzy

okay, for anyone who is interested, I think this problem is resolved. upon figuring out that I was low on 134a i tried everything I could think of to charge the system with having star to override the compressor (even running the $20 can of refrigerant under hot water to increase pressure before hookin into low side) and finally broke down and took it to a local "Benz only" mechanic. (btw if you live in the south jersey area Stuttgart auto on 206 is highly recommended) the owner Wolfgang ran diagnostics for free (almost 2 hours, recovered, vacuumed, and charged twice to be sure) and determined that my compressor was shot. I took it back the next day and four hours later my baby has cool interior again. he said when he took the old compressor off it completely fell apart. he explained in great detail (which I can't remember half of, he speaks with a thick German accent and in car language I have trouble with
that the compressor was under such strain when trying to move refrigerant that it was straining the motor and causing the sputter (abridged version). in the end it cost me 850 for the compressor, 270 for labor, and 70 for tax. 1190 out the door. oh yeah, and whatever it costs me for a new air intake hose since when I was taking mine off to look around I discovered the hard way that the last owner glued the cloth back together. yet another reason I don't like that guy. so in summary, if your motor sputters when you turn on the a/c get your compressor looked at, maybe if you get to it sooner than I did it won't need to be replaced.
p.s. thanks to everyone that helped me try to figure this out. 3.5 months in this car and almost 5 grand fixing all the things the last guy neglected. hope I'm done now. lol

samaritrey

Wow that was a very good price for the labor but to much for the compressor. I might have to check him out that is half what they wanted to charge me in my area for labor.

drtyjrzy

compressor was brand new. he won't install used or remanufactured. what do you think it should have cost? just curious.