2003 H6 Outback sometimes rough start and shakes a little when you shut off.

[roadsubiedog]

so what is this pointing too? sometimes it is rough starting and shakes a little when i shut it off. throwing a code po420. do a lot of stop and go driving to and from work for 45 minutes.

 

about a month ago it was throwing a po453 but it wasnt running bad. 

[golucky66]

Neither of those codes should realistically cause what you're noticing.

 

Without any further information, my assumption is a bad motor mount.

 

If you could explain what you mean by "rough start" that'd help. Like does it shake a lot like when shutting off. Or does it seem like it doesn't want to start.

Edited June 7, 2016 by golucky66

[roadsubiedog]

the motor "diesels" a little when you turn key off. i .e. turns over a little more than just shutting down. it used to start right up . now it takes a little longer. could it be a timing problem? 

[1 Lucky Texan]

possible combination of bad knock sensor and/or running regular gas - the manual says to run premium.

 

if you run a tank or 2 of premium and the problem gets better, might be time to check for a bad/cracked knock sensor - maybe also pull plugs and see if they are carbon coated - carbon build-up in the CCs could lead to this.

 

a:f ratio could have been rich for a while, causing carbon build-up.

[roadsubiedog]

thanks golucky and lucytexan.

 

will try and check back.

[CNY_Dave]

Since the injectors shut off the moment the key is turned off, it shouldn't diesel one tiny bit.

 

Could be a leaky injector causing both, or maybe it just has a bad motor or trans mount.

[1 Lucky Texan]

bad PCV valve 'could' let some crankcase fumes get burned - but that's a longshot. Could be something related to the emmissions code I guess, carbon canister fumes getting through a stuck-open purge valve????

 

 

I dunno, seems odd. could be just a bad motor mount as said above if the car is otherwise running well.

Edited June 8, 2016 by 1 Lucky Texan