Rough Idle on diesel

Submitted: Saturday, Jun 28, 2003 at 21:12
ThreadID: 5717 Views:1537 Replies:4 FollowUps:3
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Got a problem with a mazda bus (its been converted to a motorhome, i realise its not a $x$ but hopefully someone hear may be able to help). Since the 190K service (3,00km ago) its had a rough idle after it has been running for 25 minutes. Its fine while its cold and its always exactly after 25 minutes the rough idle starts, not affected by the distance travelled, always time dependant.

Can anyone make any suggestions as to the possible cause ?? I'm fairly new to diesel motors, own a gq with the 4.2 deisel in it, so any help on this one may come in useful at a later date.

Any help greatly appreciated
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Reply By: donc - Saturday, Jun 28, 2003 at 21:12

Saturday, Jun 28, 2003 at 21:12
sorry, slight typo there $x$ should be 4X4
AnswerID: 23743

Follow Up By: GaryInOz (Vic) - Saturday, Jun 28, 2003 at 23:41

Saturday, Jun 28, 2003 at 23:41
...no, you were right the first time!
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FollowupID: 15912

Reply By: Eric - Saturday, Jun 28, 2003 at 22:00

Saturday, Jun 28, 2003 at 22:00
donc.
Interesting question, I think it could be a tight tappet, so check the tappets, its an easy job and the same deal as a petrol . Eric.
AnswerID: 23747

Follow Up By: donc - Saturday, Jun 28, 2003 at 22:21

Saturday, Jun 28, 2003 at 22:21
Eric, thanks for the suggestion will check them out and let you know.

PS: Not quite as easy as you may think, the motors under the cab and only a smallish hatch to work thru so could be fun trying to get access to everything to check the clearances, but will endevour to do so.
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FollowupID: 15908

Reply By: donc - Sunday, Jun 29, 2003 at 20:58

Sunday, Jun 29, 2003 at 20:58
Ok, strange, but the problem has been fixed. Had to replace the battery on the bus as it had died, and this seems to have stopped the rough idle when hot. Really can't understand why this would be the case, if anyone has any suggestions as to why would be interested in hearing them.

Thanks to everyone who has posted a reply so far, all comments and suggestions noted and much appreciated

Happy holidaying and travelling.
AnswerID: 23798

Reply By: desert - Sunday, Jun 29, 2003 at 21:01

Sunday, Jun 29, 2003 at 21:01
Have you changed fuel filters of late? Had a similar problem with an Oshkosh, after engine bay heated up the crook filter seal swelled and passed air into the fuel system! Lazy mechanic was not changing the O-rings, just the filter with the previous O rings!
AnswerID: 23800

Follow Up By: donc - Sunday, Jun 29, 2003 at 21:18

Sunday, Jun 29, 2003 at 21:18
Desert,

The fuel filter hasn't been replaced at the last service, and from the looks of it, it may have been electrical, put a new battery in as the old one died and the idle problem when hot has disappeared.

Thanks for the info, and will keep an eye on it after the next service and fuel filter replacements.
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FollowupID: 15946

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