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93 400E W124
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22 Posts
Discussion Starter #1
Been having lots of trouble getting my car to pass aircare ( BC emissions testing )

93 400E, car has 196,000kms; got new wiring harness & distributors last year, new motor mounts as well. Gets regular maint. and always premium gas

After the first failure I took in to the local speciality shop and they replaced the o2 sensor. Could feel a big difference in power when driving it but failed again, even worse

Next EGR valve was replaced. Failed again
Spark plug wires & fuel filter were replaced. Numbers improved but still fails.

The car is running as well as its ever felt in the past 2 years I've had it. But without the pass I can't renew my insurance.:mad:
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,367 Posts
I recommend you replace the spark plugs with the proper type as well as all the wear & tear ignition items such as the coils, spark plugs, spark plug wires, distributors and rotors.

Make sure you use OEM ignition components from Bosch or Beru exclusively.

My '94 E320 failed smog in a similar fashion due to worn out ignition components and operator error by the smog tech by putting the car on a rolling road vs. the traditional 2 speed idle test.
 

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93 400E W124
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22 Posts
Discussion Starter #4
The shop is pretty anal about using OEM parts - Rotors n caps were Bosch, Wires from Beru, plugs were changed last year.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,367 Posts
Try running Red Line SI-1 fuel injector cleaner at full strength for the next 2-3 tankfulls (1 bottle per filling).

Then drive it like you stole it and after a couple of filllups have it retested.

Perhaps your injectors are dirty or at the end of their useful life??? Also, as I stated already, seriously consider replacing the ignition coils. The coils are consumable items.
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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12,744 Posts
You say the plugs were replaced last year. What brand/part number/type of plugs?
 
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