Dave in Texas Posted January 30, 2009 Report Share Posted January 30, 2009 When I turn Off the ignition after some miles, there is a rapid thumping noise that seems to be coming from the drivers side dash area and I haven't a clue whats under there that could make this noise. It happens more often than not, but not each/every time. Maybe something vacuum related? Everything works.......stumped! Help/advice/ideas? Thanks for any of those! GM Reman 4.1 engine Dec '08 Link to comment Share on other sites More sharing options...
KHE Posted January 30, 2009 Report Share Posted January 30, 2009 Idle speed control motor? I can't remember if the 4.1 engine had one but I think it did. It could be setting up for the next start or the closed throttle switch could be bad and it is hunting. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Dave in Texas Posted January 30, 2009 Author Report Share Posted January 30, 2009 I don't think so. This sound is from under the dash. The ISC is brand new and I recall hearing this same noise prior to the new unit. Thanks though, I appreciate it. GM Reman 4.1 engine Dec '08 Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 30, 2009 Report Share Posted January 30, 2009 I don't think so. This sound is from under the dash. The ISC is brand new and I recall hearing this same noise prior to the new unit. Thanks though, I appreciate it. Does the HVAC system appear to operating correct? If you have a door that is flopping in the fan air stream it might be slamming closed when the fan goes of. Vary the temp from AC to full heat and see if the temp varies and vary from FLOOR to DEFROST and check the operation of RECYCLE Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Dave in Texas Posted January 30, 2009 Author Report Share Posted January 30, 2009 I recycle everything I can, but I think the system only recycles in AC mode and I'm not using it when this occurs. I have noticed the something in the temp variations I put in. The temp-blends work, but don't seem accurate as they've always been. When I set to 75 the air doesn't seem very heated and I have to bump it to 80 or so. Of course, that could be my old age too! Now that I think about it, this doesn't happen in AC mode, only in Econ-Heat....odd, no? The noise is a quick-time rap/rap/rap.....from the brake-pedal area it seems like. GM Reman 4.1 engine Dec '08 Link to comment Share on other sites More sharing options...
Dave in Texas Posted January 31, 2009 Author Report Share Posted January 31, 2009 "It could be setting up for the next start or the closed throttle switch could be bad and it is hunting" ******************************************************************************** * KHE....I apologize for my doubt. The rapping noise is coming from the gas-pedal after turning the ignition Off. The pedal is rapidly moving after the engine stops. I installed the new ISC according to all the steps in the FSM and everything spec'd out correctly. I have noticed that when I ease off the throttle, the idle is around 950rpm and I have to 'burp' it to get the idle down to 750rpm where it should idle....not every time, but most times. The engine has under 300mi and I reset the computer after installing the new engine, so there hasn't been much 'learning' time for it. No codes showing. 'closed throttle switch'=TPS? Ideas? Thanks GM Reman 4.1 engine Dec '08 Link to comment Share on other sites More sharing options...
Dave in Texas Posted February 2, 2009 Author Report Share Posted February 2, 2009 Traced the problem to the new ISC. The plunger was 'hanging' and would always close the nose-switch. Installed new unit....all better now. GM Reman 4.1 engine Dec '08 Link to comment Share on other sites More sharing options...
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