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#1
09-14-2017, 12:48 PM
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M103 rough idle...yet again.
The only thing I hate about the m103 is that it seems to always develop a rough idle. I have no vacuum leaks, 2 new fuel pumps and fuel filter, spark plugs done yesterday with Bosch H9DC non-resistor plugs, K&N filter is good, even if I have the air cleaner housing off at idle it's still rough. Less than 40k miles on O2 sensor.
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 1990 190E 3.0L 
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#2
09-14-2017, 01:24 PM
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Cap and rotor? Crappy fuel? K-Jet needs adjustment? Exhaust leak? EZL? Weak ignition coil? The list goes on. The rough idle won't show up for no reason, there's ALWAYS a reason.
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Current stable: 1995 E320 157K (Nancy) 1983 500SL 125K (SLoL) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) Gone and wanting to forget: 1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]
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#3
09-14-2017, 01:47 PM
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Cap and rotor were checked with plugs last night, but I will be checking everything else that was mentioned. Fuel has always varied from different stations so I doubt they all decided to water down their fuel ��
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1990 190E 3.0L
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#4
09-14-2017, 02:23 PM
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91 300e slight idle problem
old thread same topic. I only searched the first 2 pages for M103 rough idle. What year is your car again?
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#5
09-14-2017, 02:32 PM
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Quote:
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1990 190E 3.0L
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#6
09-14-2017, 04:30 PM
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This may not sound very scientific, but did the vehicle ever have a smooth idle and if so, what's changed since then?
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Mike Murrell 1991 300-SEL - Model 126 M103 - SOHC "Fräulein"
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#7
09-14-2017, 05:30 PM
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Adding to Mike's comment above - just how rough is "rough"? Shaking the car? Dropping the mirror off the windshield? Or just a bit of annoying vibration? How are your engine mounts?
__________________
Current stable: 1995 E320 157K (Nancy) 1983 500SL 125K (SLoL) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) Gone and wanting to forget: 1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]
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#8
09-14-2017, 08:44 PM
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After spending a lot of time going through CIS-E, the first thing you need to do is look at the duty cycle and EHA amp's and report back with the findings.
Secondly probe the potentiometer and verify the voltage.
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2016 Monsoon Gray Audi Allroad - 21k 2008 Black Mercedes E350 4Matic Sport - 131k 2014 Jeep Wranger Unlimited Sahara - 62k 2003 Gray Mercedes ML350 - 122k
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#9
09-14-2017, 10:58 PM
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This is why I bought Matt's MS2 setup. CIS is finicky. Pretty reliable, but getting it running just right is a pain.
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Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.
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#10
09-16-2017, 03:02 AM
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Performed all CIS-E tests according to fsm and everything checked out within spec. Ended up removing everything I did previously when changing iacv hoses. Pulled all fuel injectors and ended up changing out one that seemed suspect with the spray pattern. Cleaned/lubricated all links with atf, buttoned it all back up. Idle was at 2500 rpm! But super smooth. Not wanting to mess with anything adjustment wise I drove car to a desolate location and opened the hood to check throttle cable and micro switch, but were fine. I then went with my gut instinct which was to check the air meter attached to the throttle body. I tapped it with a long socket extension and rpm dropped down to about 700 and was smooth.. Driving now and all is well.
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1990 190E 3.0L
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