Vibration / shake at idle
Thread Starter
Newbie
Joined: Aug 2012
Posts: 6
Likes: 1
1994 C280
Vibration / shake at idle
Hi Team
After hours and hours of reading, I still haven't been able to solve my problem.
I have a 1994 C280. When idling it stumbles "slightly" and there is a low frequency vibration. It is more noticeable in neutral (I assume) as the engine is unloaded. The car has a new Wiring Harness, New Plugs (Bosch F8DC4), New Coils, New wires, New Engine Mounts, New Transmission Mount, new fuel air filters and has been run on Mobil 1 and 98 octane fuel since day one.
No check engine light (the car doesnt have one)
It stumbles even with the MAF unplugged, and also when just started in the morning, however a bit more pronounced.
I have changed the O2 sensor, still no difference. It revs up all the way to red line with no complaints at all, and fuel consumption is still on the dot with what it were when it was brand new.
Finally this is a Euro car and has no EGR. The purge valve seems to tick away, dont know if it is ticking normally, but sure is ticking maybe around 3 or so times per second.
After hours and hours of reading, I still haven't been able to solve my problem.
I have a 1994 C280. When idling it stumbles "slightly" and there is a low frequency vibration. It is more noticeable in neutral (I assume) as the engine is unloaded. The car has a new Wiring Harness, New Plugs (Bosch F8DC4), New Coils, New wires, New Engine Mounts, New Transmission Mount, new fuel air filters and has been run on Mobil 1 and 98 octane fuel since day one.
No check engine light (the car doesnt have one)
It stumbles even with the MAF unplugged, and also when just started in the morning, however a bit more pronounced.
I have changed the O2 sensor, still no difference. It revs up all the way to red line with no complaints at all, and fuel consumption is still on the dot with what it were when it was brand new.
Finally this is a Euro car and has no EGR. The purge valve seems to tick away, dont know if it is ticking normally, but sure is ticking maybe around 3 or so times per second.
Thread Starter
Newbie
Joined: Aug 2012
Posts: 6
Likes: 1
1994 C280
Some more info:
Sometimes in the mornings when I start the car it starts a little bid odd. Let me elaborate.
If the normal crank and then start sounds like "Ca-huhahuha" and then its running, the "Ca" being the starter motor engaging, "huhahuha" being the cranking.
Some mornings it just goes "ca-hu" and before the first "ha" the engine is running.
Apologies for the comical description, but I felt it was the best was to describe this.
Sometimes in the mornings when I start the car it starts a little bid odd. Let me elaborate.
If the normal crank and then start sounds like "Ca-huhahuha" and then its running, the "Ca" being the starter motor engaging, "huhahuha" being the cranking.
Some mornings it just goes "ca-hu" and before the first "ha" the engine is running.
Apologies for the comical description, but I felt it was the best was to describe this.
Junior Member
Joined: Feb 2012
Posts: 17
Likes: 0
1994 MB C220
If your already change your MAF and O2 sensors, Check your EGR valve. This is one of the components that are usually had been overlooked that has great affect on idling. It cant always be detected by fault reader because it's semi-mechanical or mechanical in nature. Sometimes it stick open because of carbon deposit of years being build-up. Sometimes you notice at 1st start of the engine while idling it seemed smooth, but when you tap on the gas pedal it activate the vacuum switch to open the valves, but this time it sticks, now you have a rough and extremely low rpm.
Junior Member
Joined: Feb 2012
Posts: 17
Likes: 0
1994 MB C220
Oh sorry about that I overlooked it… well it could also be the “throttle body wiring harness.” It must be toasted and wires are sticking together to create a short. I had a surprising discovery with my 1994 c220 recently after checking (scanned) all possible components that relate to bad idling, the throttle electrical cable are burned and wires are sticking inside. It looks like a fine looking cable apparently but when I peeled it off to expose a wire, opened the actuator/potentiometer cover, and quickly jumped into conclusion that this is the problem that I’m chasing. Now my 18 years old car running like brand new…
Junior Member
Joined: Sep 2012
Posts: 26
Likes: 0
1995 C280 sport
My does almost the same thing it is a 1995 c280 sport. I have no Idea what is wrong with it I just know that when I'm stopped at a red light the entire car shakes. It varies from time to time. Sometimes it is just a small shake while others it is a very violent shake I cant seem to find out what it is also occasionally it wont do it at all.
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Junior Member
Joined: Sep 2012
Posts: 26
Likes: 0
1995 C280 sport
My car is no longer shaking thanks to this.
Goodluck.
Newbie
Joined: May 2021
Posts: 1
Likes: 0
C220
So I found out what is causing my problem. Someone showed me this video on how to check if it is motor mounts.
http://www.youtube.com/watch?v=bUl2H...feature=relmfu
My car is no longer shaking thanks to this.
Goodluck.
http://www.youtube.com/watch?v=bUl2H...feature=relmfu
My car is no longer shaking thanks to this.
Goodluck.
Can you please describe what you do to solve it ??
Thanks very much
