LINDAL Posted December 8, 2012 Report Share Posted December 8, 2012 Just threw a pcm p0171curtent Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 8, 2012 Report Share Posted December 8, 2012 Just threw a pcm p0171curtent OK good, you HAD a P0174, now you are getting a P0171 rear bank lean..... Look around the engine carefully for vacuum leaks at the brake booster and the PCV valve, if the connections are good and there are no cracks, look at the intake plenum 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...
LINDAL Posted December 9, 2012 Report Share Posted December 9, 2012 We took the MAF out and put the old one back in. Look at all the hoses and the plenum part. We cant see anything wrong. It is still missing and surging. I reset codes took it for a drive and it is showing both 174 and 171 again. Now what? Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 9, 2012 Report Share Posted December 9, 2012 THAT IS GREAT. Typically the plenum leaks on the bottom, you can not see the leak it is probably split in a fold of the plenum. The reason it leaks on the bottom is because condensed EGR gases settle there and create this primordial goo that degrades the rubber material. You can attempt to spray some carb cleaner under it with on of those red tubes to see if the idle changes. But given the year of your Northstar, this is a common failure and symptom. 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...
Texas Jim Posted December 9, 2012 Report Share Posted December 9, 2012 We took the MAF out and put the old one back in. Look at all the hoses and the plenum part. We cant see anything wrong. It is still missing and surging. I reset codes took it for a drive and it is showing both 174 and 171 again. Now what? Not idling right... Surging... Lean codes on BOTH bamks... Looks like it is time to change the plenum... Link to comment Share on other sites More sharing options...
Logan Posted December 9, 2012 Report Share Posted December 9, 2012 The diagnosis is clear. Bad rubber intake plenum boot. Here is...a second opinion... http://www.justanswer.com/cadillac/486ai-2000-cadillac-northstar-engine-idols-rough.html Logan Diagnostic LLC www.airbagcrash.com www.logandieselusa.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
airmike Posted December 10, 2012 Report Share Posted December 10, 2012 We took the MAF out and put the old one back in. Look at all the hoses and the plenum part. We cant see anything wrong. It is still missing and surging. I reset codes took it for a drive and it is showing both 174 and 171 again. Now what? As previously stated if you will take some carburetor cleaner and spray it at different spots on the engine you will be able to locate the leak easily. If sprayed at the bottom of the plenum boot and the idle changes you definitely KNOW it is leaking there. If a possible leak is at any other hose, same thing. That will eliminate the guessing, although the boot ultimately will likely be the leak. It is very cheap and easy to do. Link to comment Share on other sites More sharing options...
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