96 S320 ROUGH idle & running - Mercedes-Benz Forum

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Old 04-28-2008, 06:49 PM   #1 (permalink)
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96 S320 ROUGH idle & running

symptoms: really rough idle, needle jumping from 500-1200 rpm even during a slow crawl, sometime's almost dying. i replaced the egr valve, seemed to run a WEE bit better, but symptoms showed up again. ran the engine, disconnected the MAF sensor and the engine got worse, so looks like that isn't the culprit. i'm hearing a really soft electric-like sound coming from underneath the passenger-side back seat, that coincides with the reduction in rpm, kindof like an acutator trying to do something ???

i connected an obdII reader, but no codes showing up. what else can i do? i bought new spark plugs, since the car has 87k miles, and it's time for a tune-up. also changed the air filter today. i haven't changed the fuel filter yet.

please help!!
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Old 04-28-2008, 06:59 PM   #2 (permalink)
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Well , i still have the same symptoms even after rewiring ETA .
Do you know someone with m104 engine ,to borrow MAF sensor and see if its gonna help?

But i tell you,wires in ETA were bare,i could not trace them with Ohm meter ,to rewire,I had to do one by one,instead of just drawing diagram,and just cutting them.
Yours is 96,so check your MAF wiring first,before digging into ETA,check Jonathan Wallin posts.
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Old 04-28-2008, 07:10 PM   #3 (permalink)
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thanks.

i also forgot to add....

the rubber hose connected to the EGR valve, should that have a strong vacuum? i notice little to no vacuum when i disconnected it with the engine running.
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Old 04-28-2008, 07:30 PM   #4 (permalink)
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I use MityVac and 5 bars was enough to cause engine go nuts.


Anhtuanle ,can you do me a favor ,after i rewired my ETA ,its running constantly you turn the key to illuminate all lights,but dont start,and i hear this buzzing noise from ETA,sounds ,like motor is running all the time ,yo can hear it with hood open,I dont know if it was running like that before ,can you check your car and let me know if you hear noise coming from ETA ,I put my ear where air intake is going into the ETA.
Thanks.
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Old 04-28-2008, 07:40 PM   #5 (permalink)
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will do. i'll have to wait to check tomorrow evening.
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Old 04-28-2008, 07:45 PM   #6 (permalink)
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thanks,will wait for the result.
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Old 04-28-2008, 09:29 PM   #7 (permalink)
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Originally Posted by anhtuanle View Post
thanks.

i also forgot to add....

the rubber hose connected to the EGR valve, should that have a strong vacuum? i notice little to no vacuum when i disconnected it with the engine running.
The vacum hose to the EGR valve comes from the EGR solenoid. The EGR is disabled at idle, so the solenoid should not provide any vacuum to the EGR valve. Please correct me if I am wrong, but that's how the EGR system works on Cadillacs. Should be same on a Benz I guess.
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Old 04-29-2008, 03:34 PM   #8 (permalink)
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thanks,will wait for the result.

hey symbolic95, looks like your rewire is ok. i can hear the eta running when the key is in the on position, but the engine isn't running.
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Old 04-29-2008, 04:59 PM   #9 (permalink)
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thanks man , now i can sleep well,but not idle
i'll try to trace the vacuum and see if its leaking ,will keep you posted
BTW welcome to the forum
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Old 05-01-2008, 12:03 AM   #10 (permalink)
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did you rewire YOUR ETA? or did you swap it on core exchange basis? if the throttle is replaced, you need a STAR scanner to code it to the PCM.
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