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Originally Posted by mack1a  I know I have seen something on the following somewhere in this forum but I can't find it. I probably am too impatient to wait for a search on this site.Twice when I have stopped at an intersection about 1 mile from my house I have heard a knocking sound that sounds like someone is in the trunk. It happens 5 or 6 times then disappears.Again, I know I have seen this on the forum but can't find it. I believe it was something to do with the fuel system. I would appreciate someone refreshing my memory on this if possible. |
"GM Service Information Bulletin Document ID# 1856743 2006 Cadillac DTS; Exhaust Noise on Cold Start Up - keywords 4.6 air LD8 L37 leak pump secondary #PIP3546A -(08/18/2006)
Condition/Concern: Some customers may comment of a pulsing noise from the engine that ocurs during the first minute when starting the engine after sitting several hours. It is actually normal combustion noise caused by aggressive fuel and spark to heat the catalytic converters in order to meet more stringent 2006 model year emission requirements." In my case it happens in cooler weather, car stopped or coasting to stop at low (under 1000 rpm), temp gage at 8 o'clock, get 5 taps in right rear. I mean taps, not pulses but in my opinion the above pulses cause the taps, probably from a loose baffle in the exhaust. If I left the car overnight and started it (cold) at the dealer's I'm sure that 4 out of 5 times I could show the taps. Just haven't bothered to push it. Wont happen under acceleration or on the highway in my case. Otherwise I love the car. I'm 6'-6" and the range of driver seat adjustment was a major plus versus anything else that could also handle two suitcases and three golf bags in the trunk. Good luck all!