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#3266666 - 02/01/14 09:45 AM Mitsubishi Diamante rough idle
Spetz Offline

Registered: 01/23/14
Posts: 211
Loc: Australia
My 6G74 SOHC Diamante has a really poor idle.

Does so in D, R and to a lesser extent in N.

Things tested to be fine:
O2 Sensor
MAF Sensor
ISC (idle speed also fine as per computer data logging)
Engine Mounts

Things replaced:
All spark plugs
Air filter, fuel filter, oil filter and oil
Valve cover gaskets
PCV valve cleaned, TB Cleaned

Idle gets quite bad after long running times.
At some stage it felt like it idled better after cleaning the PCV and changing rocker cover gaskets but poor idle returned (could have been coincidental).

It feels almost like it sporadically misses and shakes the car.
Drives completely fine and engine is smooth other than at idle.

Any advice would be greatly appreciated.
2003 Mitsubishi Diamante 6G74 3.5L. 5 Speed auto. 130,000 miles

#3266678 - 02/01/14 09:57 AM Re: Mitsubishi Diamante rough idle [Re: Spetz]
GumbyJarvis Offline

Registered: 08/23/11
Posts: 1416
Loc: Fort Hood, TX
Coil pack? Maybe coil going
2013 Dodge Dart SXT 2.0L 40k MI
German Castrol 0w40 + Fram Ultra 10060
DC Sport Exhaust, K&N Cold Air Intake
Alpine Audio

#3268695 - 02/03/14 12:49 AM Re: Mitsubishi Diamante rough idle [Re: GumbyJarvis]
artificialist Offline

Registered: 09/23/07
Posts: 7730
Loc: Florida
Originally Posted By: GumbyJarvis
Coil pack? Maybe coil going

Good point.

Also, back then many Japanese cars had distributors that were a common problem. Discount rebuilds only last 1 year.
2010 Lancer Ralliart Sportback