Question about 2002 Cadillac Deville

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Motor is reving up and then back down

At first I thought it was water in the gas line and was told by the dealership to get the water treatment. It is still doing this. When sitting at a stoplight my engines revs up and then back down. I put the setting on the rpms and it starts at about 700 then drops to 650 then drops to 550 and back to 625.

Can you tell me what might be causing this?


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  • ckoffee Dec 26, 2008

    This is a 2002 Cadillac Sedan Deville with I think a 4.3 or 4.2 Northstar V8 engine

  • ckoffee Dec 29, 2008

    Well, I went to the Cadillac dealer and had this checked out. They ran the DTC Check and came up with P0171/P0174 which was a torn intake boot. So they installed a new one, which cost me $500 (the part was $30 and the rest labor), but it runs so smooth I can't even hear the motor running.

    Thanks for your help.

  • jdtech May 11, 2010

    What is the make ,model, and engine size. These symptoms could be a misfire or an air/ vacuum leak.Possibly EGR related



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Torn intake boot on 2000+ Northstar requires removal of intake manifold along with injectors-about 4 hour job not just 2 clamps as suggested. New seals required could also run past $100 so $500 is not unreasonable

Posted on Oct 19, 2009

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More possible suggestions...coolant temputature sensor .. TPS or even mass airflow sensor ... you should get codes checked for soft codes and real time monitoring to see if sensors are in their proper range /window ... please advise once you have it tested

Posted on Dec 26, 2008

  • milespeed Dec 29, 2008

    excellent ..glad she i s healthy again... ouch... that labor is insane... the snorkel they replaced is only hose clamped on both ends and only takes 20 minutes to do...



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