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Old 05-13-2010, 03:51 PM   #1
Join Date: Jan 2010
Location: New Carlisle, Indiana
Posts: 48
Year: 1995
Coachwork: carpenter
Chassis: spartan
Engine: 5.9 cummins
Rated Cap: 84
Vibration at Idle

Hi, I have a 1995 carpenter flat nose front engine, 40 ft. bus. It has a 5.9 cummins with 125,000 miles on it. It runs great but at Idle it vibrates the bus. If I take if just off idle it smooths out. I was told that is normal. I was wondering if I can do anything. Maybe get the idle turned up some? Any Ideas?

Thanks MAJ
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Old 05-13-2010, 03:56 PM   #2
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Join Date: Feb 2007
Posts: 4,075
Re: Vibration at Idle

My 86 Intl does the same thing. It drives me nuts at idle. I was going to try to bump the throttle a hair.
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Old 01-23-2011, 06:26 PM   #3
Join Date: Apr 2010
Posts: 14
Year: 1989
Coachwork: Bluebird
Chassis: TC2000
Engine: 5.9
Rated Cap: 45
Re: Vibration at Idle

Ok, I am not an expert, but this is what I found. I bought a set of used 7mm injectors due to a recent head change. I put it back together, and had a very rough running bus. (89 model with 5.9 BTA, and a VE rotary pump).

First make sure all cylinders are firing. Do this with a cold engine, and stay clear of the turbo. Start the engine and feel each exhaust flange. You will notice that each will warm within a minute. Often there is a cold one or two. Make notes on these.

Shut the engine down , remove the injectors from the cold cylinders. Have a shop check them for spray etc. Mine were not spraying, but dripping. You will see this with black smoke in the exhaust too.

6 new injector nozzles, the engine runs like a smooth diesel...

Remember, i am new to diesels, but have many years on Jet engines.
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Old 01-23-2011, 07:59 PM   #4
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Join Date: Nov 2003
Location: Twin Falls, Idaho
Posts: 806
poor Idle

If the engine has glow plugs, remove and check compression. Replace the plugs after noting the compression values. Add a quart of Power service to 20 gallons of diesel fuel. After 250-350 miles, check the compression again. Any increase of compression will be noticed and the idle will be improved. Doing a compression test is very important to check engine condition. Some times I add a quart of water thru the top of the engine with the air cleaner removed. Make the engine turn about 2000 RPM and pour water into engine slowly so engine does not stall. Place an empty paper box at rear end of exhaust pipe to give evidence of removed carbon. Keep engine at 2K rpms for a short time. Allow engine to idle for a couple minutes. This is a quicky tune up. Frank
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