'01 E430 4matic, no codes but rough idle

[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

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[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]

Originally Posted by 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.

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]

Originally Posted by 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.

thank you for advice, I will check it out

[tn6020]

Originally Posted by 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.

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]

Originally Posted by 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

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]

Originally Posted by RichardM98

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.

This Idea is the best for me.Thanks a lot