[deville05]

2005 DHS. Seems to slightly speed up when I press the brakes. Can feel it slightly and it's annoying. Any ideas?? Also seems to have a largish clunky feeling sometimes when I speed up.

 

[basscatt]

2005 DHS. Seems to slightly speed up when I press the brakes. Can feel it slightly and it's annoying. Any ideas?? Also seems to have a largish clunky feeling sometimes when I speed up.

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check for Diagnostic Trouble Codes -
if you don't know how - go here and read the ENTIRE post -

http://www.cadillacforums.com/forums/cadillac-deville-1985-2005-including-1985/138257-how-pull-codes-dtcs.html

if you have any codes - post them here -
ALONG WITH THEIR DEFINITIONS -

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check for a broken front motor mount -

 

[deville05]

Codes pulled.. Here is what was found.

IPC
U1016 Loss of Class 2 Communication with VCM
U1000 U1000 Class 2 Communication Malfunction

IPM
B0429 Temperature Control #3 Rear Circuit Range/Performance
B1004 Keep Alive Memory (KAM)

PDM
B1913 Heated Seat Switch - Mode Input Shorted to Battery
U1714 Something about power window. All work fine.
B2507 - RF LAMP HIGH BEAM CIRCUIT Failure
U1000 Class 2 Communication Malfunction

 

[reppinshadyvill]

Check for vacuum leaks.

 

[needwater4230]

My money's also on a vacuum leak - sounds like you're experiencing surging.

 

[deville05]

Ok. I will check all the vac hoses this weekend. Will probably pull the throttle body and check for holes in the boot. Probably needs a good cleaning anyway. Preparing for coolant crossover gaskets in the future. Dealer that I purchased the DHS from recommended them being done. Been watching coolant levels like a hawk. No changes in 3K miles since I purchased it. So far so good. Engine has a very rough idle on cold and warm startup that goes away in a few minutes. No missfire codes showing. Maybe a plug replacement this weekend also.