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Excessive shaking on startup of cold engine

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H

Howard

Lifer
This morning, and Friday morning, there was a lot of shaking when I started up the engine. I did drive during the weekend so I guess it doesn't always happen even if the engine hasn't been warmed up.

Anyway, I don't think I hear any weird sounds when it happens, and it goes away in about 10-15 seconds after the engine starts up. I don't believe it's ever occurred when the engine is warm, though the problem has started only last week.

2005 CTS with 2.8L engine, manual tranny
 
Sounds just like when we had a plug fouled on our Blazer. Changed the plugs, went away to never return. Of course, we'd put in junk plugs a few thousand miles before it happened--Autolite Plats---changed back to the AC Delcos and never returned.
 
Third on the plugs / plug wires. It's cheap to do anyway, so it's a good starting point. If you want to save even more cash, you can go through the trouble of changing out the spark plugs, then swapping a known good wire (test with ohm meter / Google for normal range) to a different cylinder and seeing if the symptoms persist.
 
That happened on my car, and the coil wire was bad. I went ahead and changed all the plug wires since it was due for it anyways. It hasn't given me a problem in the 30k miles since I changed them.
 
If you want to throw parts at it, you're free to do so. There are lots of parts out there, so it can keep you busy for a long time. You will eventually fix the problem though.

This should be easy to correctly diagnose if you have a scan tool hooked up when starting, assuming the problem can be reproduced at that time. You'll need a scan tool that can take a snapshot and regurgitate that data.
 
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