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  #1  
Old 07-29-2008, 06:23 AM
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Join Date: Nov 2007
Location: Texas
Posts: 16
cold engine miss sometimes

Hello all,
On my 90' 300D sometimes with the engine running cold just after start up it will miss or stumble some. This previously happend over the winter at times but temps were obviously much colder than now in the summer here in north Texas.
I use the same fuel station each fill up and add diesel kleen cetane boost.
I use Wix fuel and oil filters at scheduled intervals with Mobil diesel oil.
The car runs great in all areas and this condition goes away quickly with warmup but I would still like to remedy the problem.
I'd like to add that this little turbo diesel is a freeway burner. Such smooth steady pull upon request and the suspension for its age is solid.
We enjoy the car and even at 4.75 a gallon average here, the car is paid for and one would be hard pressed to find another vehicle that gets as good a fuel milage with this much tourqe, quiet ride and quality build.
Of course I'm sure you all already know this, you drive these great cars too!
Anyhow any advise or knowledge on the cold engine miss is greatly appriciated. Thanks!
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  #2  
Old 07-29-2008, 06:33 AM
Gene
 
Join Date: Mar 2007
Location: Buffalo NY
Posts: 1,082
A compression/leakdown test showed air getting past the valves, and I thought it would cure the cold miss ( and smoking). Nope. A compression/leak down test will show how tight the engine is. WARNING: its not an easy job, like on a pushrod V8.

Check all your fuel lines for air bubbles. There should be none. If there are you'll have to isolate the air leak. Common is the pre filter o ring seal. I also changed out the delivery valve seals ( with Viton) as they were leaking. Leaks and diesels are a NO GO.

Lastly, the known cure for my cold start miss - B100!!!!!! It radically mitigates it.

As far as I can tell, I have a piston ring leak ( which I'll confirm with a compression test fdown the road), or an IP rebuild. Neither are required right now, so..
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  #3  
Old 07-29-2008, 03:37 PM
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Join Date: Nov 2007
Location: Texas
Posts: 16
Thanks for the info, I'm leaning towards fuel issue.
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  #4  
Old 07-29-2008, 07:19 PM
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Join Date: Jan 2006
Location: Northeast Indiana
Posts: 10,767
Check the resistance of each glow-plug, possible one of 2-5 is bad. You won't get a bad glow-plug indication from the light unless 1 is bad or two of 2-5.
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  #5  
Old 07-29-2008, 08:28 PM
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Join Date: Oct 2003
Location: Montreal, Canada
Posts: 737
1) See if it makes a difference whether your fuel tank is full or less than 1/2 full, when it happens.

2) Does it make a difference if you park facing one way or another?

If yes to any of the above, than you most likely have a fuel leak somewhere.
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  #6  
Old 07-30-2008, 03:06 PM
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Join Date: Nov 2007
Location: Texas
Posts: 16
Thanks guys I'll do some checking and get back to you. Much appriciated. Rob
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  #7  
Old 07-30-2008, 03:46 PM
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Join Date: Dec 2004
Location: Sonoma County, California
Posts: 1,062
I agree with the glow plug idea. I had a similar problem and found a bad plug so that cylinder didn't fire properly on start up but it would clear as soon as it started to warm up. New plug and no more problem.
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