Engine Choking/Revving on Cold
Thread Starter
Junior Member
Joined: Jan 2021
Posts: 25
Likes: 1
From: Melbourne, Australia
W204 2008 & W163 1999
Engine Choking/Revving on Cold
Does anyone know what would cause the engine to choke slightly on cold starts. I am in Melbourne Australia, and the temps dont get too cold/warm, but it always happens every morning.
It would choke and I can feel the car slightly hesitate each time - however once the engine reaches temperature, its like nothing happens and everything is normal.
Havnt taken to mechanics as I would like to know a bit more before asking for their professional service.
EDIT: Ignore the PRE-SAFE as the engine choking had already started and that Presafe only started after I knocked the wires underneath the passenger seat while cleaning the car and its related to the AirBag which I have to fix up.
It would choke and I can feel the car slightly hesitate each time - however once the engine reaches temperature, its like nothing happens and everything is normal.
Havnt taken to mechanics as I would like to know a bit more before asking for their professional service.
EDIT: Ignore the PRE-SAFE as the engine choking had already started and that Presafe only started after I knocked the wires underneath the passenger seat while cleaning the car and its related to the AirBag which I have to fix up.
Last edited by zolthar; Sep 12, 2024 at 08:27 PM.
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2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
What model & engine?
How many miles/km?
Since it is only happening before the car reaches operating temperature, it’s an open loop problem. Something is getting out of spec, but not so far out that the ECU can’t correct for it after engine warms up and goes to closed loop. Hard to diagnose because it goes away. Suspect injectors, throttle body, MAF, PCV systems. Need to scan car with a Mercedes specific scanner and see if there are any leading indicators.
In the video, it looks like the car is already warmed up but RPMs are still “hunting.” Maybe monitoring fuel trims could help after scanning.
How many miles/km?
Since it is only happening before the car reaches operating temperature, it’s an open loop problem. Something is getting out of spec, but not so far out that the ECU can’t correct for it after engine warms up and goes to closed loop. Hard to diagnose because it goes away. Suspect injectors, throttle body, MAF, PCV systems. Need to scan car with a Mercedes specific scanner and see if there are any leading indicators.
In the video, it looks like the car is already warmed up but RPMs are still “hunting.” Maybe monitoring fuel trims could help after scanning.
Last edited by Odd Piggy; Sep 13, 2024 at 01:36 AM.
Thread Starter
Junior Member
Joined: Jan 2021
Posts: 25
Likes: 1
From: Melbourne, Australia
W204 2008 & W163 1999
Hi, my apologies for not providing the important details:
W204 2008 Petrol
260000km
Model 204.041
Engine 271.950
Ill check tomorrow morning the exhaust and see if anything suspicious and will test the MAF and disconnect and will update.
W204 2008 Petrol
260000km
Model 204.041
Engine 271.950
Ill check tomorrow morning the exhaust and see if anything suspicious and will test the MAF and disconnect and will update.
Thread Starter
Junior Member
Joined: Jan 2021
Posts: 25
Likes: 1
From: Melbourne, Australia
W204 2008 & W163 1999
Tested yesterday and today, since I disconnected the MAF drove a bit that triggered the CEL, during which the engine didnt choke until warm. Reconnected and drove more and it hasnt choked this morning.
When engine was started in Sunday morning, there was only a bit of white puff from the exhaust for about 20s and then nothing - so I am assuming that was just some moisture and a nothing.
Ill get some MAF cleaner and give it a spray and see if that helps further or until it starts again and will stop by a garage to get it scanned.
Thanks for the tip Odd Piggy.
When engine was started in Sunday morning, there was only a bit of white puff from the exhaust for about 20s and then nothing - so I am assuming that was just some moisture and a nothing.
Ill get some MAF cleaner and give it a spray and see if that helps further or until it starts again and will stop by a garage to get it scanned.
Thanks for the tip Odd Piggy.
