Why does my Mercedes 300E run rough at idle?

My 92 300E (2.6L) starting running rough the other day, like it is missing. This was not a progressive problem, but started to do this one cold rainy morning a few days ago. The car shakes at idle and light acceleration, and seems to be an engine miss and not just bad motor mounts (although I am not ruling anything out).

How to tell if a Mercedes 300e is dead?

To see if you actually have a completely dead cylinder, you can test each one by removing a plug wire one at a time with the engine running. When you get one that makes no difference, that’s your dead cylinder. Yep, done almost everything mentioned, but still really appreciate all the input.

What kind of car was the 1991 Mercedes 300CE?

The coil in our daughter’s 1991 300CE failed while driving and the engine wouldn’t run. ( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone) 1997 s320 154k (what a ride).

What kind of plug does a Mercedes 300E use?

Car has only 100K on it, a very low mileage 300E. I put in Autolite 104’s, which is a non-resistor plug that many other W124 owners are having good success with. (I realize the spec plug is a Bosch H9DC).

Is the O2 sensor on my 87 300E working?

Since your car is low mileage and 18 years old, I’m sure the O2 sensor is original, since they only last about 100,000 miles now might be a good time to change it anyway, even if thats not the problem. My 87 300e had a shot O2 sensor when I first got it.

How to troubleshoot an automotive engine high idle?

The troubleshooting procedure for high and low idle conditions are similar, which are included in the following: Step 1 – If the check engine or service engine light soon has illuminated retrieving the diagnostic trouble codes could lead you in the right direction of what the problem is, or is related too.

Why does my car rev up when idling?

If your car seems to be revved up to a higher-than-normal RPM while idling, it’s not necessarily a problem. If this problem happens while the engine is cold, it may be part of the engine’s design.

What does accelerated idle mean on a car?

But if the accelerated idle persists even after the engine is fully warmed up, it probably indicates a genuine problem. The first step is to determine if there are any diagnostic trouble codes stored in the PCM (powertrain control module). If there are, this will give you a good starting point for troubleshooting.

How can I check the idle air control?

To perform a rough check of the idle air control, remove the valve while reconnecting the wiring harness. While observing the valve with a flashlight, turn the key to the “ON” position, (DO NOT START ENGINE.) the valve should move slightly.

What’s the problem with my Mercedes 300 CE Coupe?

25 people found this helpful. i have a 300 ce coupe 1988 starts when cold let it run to warm up switch it off then wont start and my idle seems to fluctuate never runs smooth and when im driving it come to a stop it stalls. any advice on this problem will be thankful. 16 people found this helpful.

Why is my Mercedes Benz 300 not starting?

However ther are many causes here, poor ignition coil, fuel filter, fuel pump etc etc. You will need to check these items when the car is in a ‘failed state’.

Is the Autolite 104 good for a 300E?

Your injectors may have a poor spray pattern if the miles are high. Car has only 100K on it, a very low mileage 300E. I put in Autolite 104’s, which is a non-resistor plug that many other W124 owners are having good success with.

What to do if your Mercedes 300 starts?

You will need to check these items when the car is in a ‘failed state’. Carry a spare spark plug so that you can pull a lead off and earth the body of the plug to the engine, crank the engine and you should see a spark, this will illimnate the ignition as at fault, if you have a spark then i would look into the fuel system.

What was the 1985 Mercedes-Benz 300SE fuel pump?

1985 300se new pumps –acumulator–fuel pressure unit– distributor– injectors –starts–sometimes a few revs– then wont keep on going– was on gas for a long time –hence the new system– why wont it keep on going 6 people found this helpful.

What causes rough idle and low rpm at startup?

You start the engine cold and it will hardly run. It runs rough and idles very low and will even quit a few times. You may also notice that your ABS light comes on. After the engine warms up idle speed will increase and the engine may smooth out (although acceleration may have some hesitation until the engine gets real hot.

When does the ABS light come on at idle?

You may also notice that your ABS light comes on. After the engine warms up idle speed will increase and the engine may smooth out (although acceleration may have some hesitation until the engine gets real hot. But, the ABS light may continue to stay on while driving and you may experience a pulsing pedal when you stop (not always).

Why does my car idle when the EGR valve is not open?

As long as your EGR valve fails to open or close, your engine won’t idle properly, which implies that there is not enough gas entering the vehicle’s internal combustion chamber. This is the reason why your vehicle will idle roughly.

What’s the code for an EGR valve throw?

What code will an EGR valve throw have? The P0401 trouble code is related to your car’s exhaust gas recirculation (EGR) system, which controls an engine and reduces emissions. Suppose a computer-controlled valve gives a certain amount of gases back into your engine to be burnt with the air-fuel mixture.

Why does my 1990 Ford 190E not start?

You may be surprised to see what Kent found was the cause of the starting problem he was having on his 1990 190E 2.6. The car would start and then quit. Or it would start and round weak and rough for a minute before coming to live. It would also idle too low during cold startup. The problem turned out to be a simple and inexpensive fix.

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