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1997 C230 rough idle at 500 rpm. No problem over 500 rpm

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1997 C230 rough idle at 500 rpm. No problem over 500 rpm

 
Old 03-11-2019, 01:14 PM
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1997 C230 & 1992 300E
1997 C230 rough idle at 500 rpm. No problem over 500 rpm

1997 C230 is idling rough at 500 rpm. No problem if idle is over 500 rpm.
Was getting codes P0300, P0301, P0302, P0304; now there are no codes showing after replacing all spark plugs, both coil packs, air filter, oil change & filter and Techron fuel system cleaner in gas tank. Car has 119k miles & was working fine prior to a week ago & it's near time for 120k maintenance.
After replacing CHP71 spark plugs with Platinum plugs, car runs much better; but still rough idle at 500 rpm.
CHP71 spark plugs taken out were only a week old and were burnt & smelled a little like gasoline. These previous plugs were installed by a different mechanic shop that installed new coil pack on #1 & it should have been installed on #2. I had to buy 2 new coil packs & new plugs and switched mechanic shops.
Vacuum hose connector broke (it's on order from parts store).

Mechanic idled car up to 10 rpm and car runs good, but is this bad for the car to run that high at idle?
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Old 03-19-2019, 02:20 PM
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1999 E320 Wagon 4Matic
Usually the idle speeds setting is specified with tune up info. You don't want to have 1000 RPM idle if the spec is 500. That would mean the car is more likely to creep ahead when you are on the brake at a light and is generally not ok. I don't think it a major wear and tear issue though...

If you are saying there is currently a vacuum leak, that should be repaired first and then idle should be set back to spec. small vacuum leaks can definitely affect idle performance.
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Old 03-21-2019, 06:00 PM
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1998 C230
you need a complete tuneup and on that vehicle change all the vacum hoses because the rest is dry rotted also
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Old 03-22-2019, 01:18 AM
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1997 C230 & 1992 300E
Will do. Thanks
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Old 03-22-2019, 09:27 AM
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1998 C230
Benz lady

Over 500 rpm it will seem to be running good but you need it to idle smooth so gas ,air an spark is needed in sync. So plugs, air filter, coils, vacuum hoses,pcv valve. cam and crank sensor and gas filter needs to be installed. I would also use premium gas and half can of seafoam take for a run i guarantee all will be well after
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