tn6020

Hi everyone when I got My '01 E430 4matic at 100 Kmi. the car run great but very poor mileage (14-16 mpg), rough idle when stopped at the red light, no CEL but got the code for 2 front Oxygen sensors problem, I did used many times of Injector Cleaner and also replaced those 2 sensors by a recommended Bosch brand but problem still resists, although mileage now a little bit better (16 mpg combined) and the car is running great, and, NO CODES to be detected but Idle still very rough
Does everyone have this issue before and so please give me an advice how to fix this. Thanks in advance

ohlord

change your spark plugs they are past due.
0w40 mobil synthetic,fleece filter.
Check tire pressure correct.
if the rear o2's are getting old and sluggish they affect the ecu and the signals to the mass air sensor,so it will help to replace them also.

RichardM98

I'd vote for checking plugs, plug wires and coils. Sounds like maybe a miss. Probably always there but mostly noticeable at idle. As mentioned plugs should be changed at 100K as well as O2 sensors.

ohlord

to the poor mpg,rough idle without codes for misfires,inspect your motor mounts. If leaking they will cause idle shake at lights and in neutral.

tn6020

I got an oil changed at MB dealer, dont know why they used Valvoline instead of Mobil 1 0W40 as factory reccomended, about the 2 rear O2 sensors, Actually I do not feel good to replace for now bc of budget limitlity, but I will replace air filter and clean the MAF then if nothing beter I will go to spark plugs and wires

tn6020

thank you for advice, I will check it out

tn6020

thank you for the Idea, is the cost for replace wires is not too rough ? I have very small budget due to the job has been down for now

RobertG

If you are on a tight budget then hold off on the wires and do the spark plugs.
When you pull the plugs inspect them, they might tell you what is going on in the combustion chamber.(misfire or rich condition)

RichardM98

Here is the US a set sells for about $175. If you have access to a multimeter (Digital Volt/Ohm Meter) you can measure the resistance. There is a spec for the resistance but I'd have to look it up. However to do so you need to remove the wires and there is some risk of damage doing so. An offset 17mm wrench is often used to 'pry' off the metal hood on the plug end.

If you were getting codes for a misfire you could move the plug wires and/or the coils to a different cylinder and see if the codes follow.

With a tight budget maybe the best solution would be to get the car scanned with SDS at dealer or indy. Even though you will have to pay for that you will avoid installing parts which may not help.

tn6020

This Idea is the best for me.Thanks a lot

lovestarbucks

Hi I have a 2001 E430 with 120K and the dealer recommended full tune up, Service B was due and Tires. I did all the above to pay a hug bill. Yet to find the car still has a rough idle in Park, N and when standing still, while accelerating or cruising at 65 mph no roughness. As I read more about the issue. Some people are saying tough luck deal with it, u till I came across your lost about Motor Mounts. If the motor mounts are bad they could cause rough idle? How do you check Motor Mojnts, as well as checking if they are leaking?

If that's the case did the vehicle really need the service the dealer performed?

Thanks Johnny H

RichM

Motor mounts are fluid filled, and dampen vibrations from the engine thus isolating you from them. Bad motor mounts can make the car feel like there is a rough idle as they are no longer isolating these vibrations. Look for fluid staining on or around the mounts. At 120K miles, if the plugs have never have been changed it is time.