jamesc Posted January 7, 2009 Report Share Posted January 7, 2009 Car states up quickly, shakes while sitting, had injectors clean, plugs changed, fuel filter changes, plug wires/boots replaced, and the vehicle still runs bad. Help, Help, Help Link to comment Share on other sites More sharing options...
dgaouette Posted January 7, 2009 Report Share Posted January 7, 2009 What codes are set?? Link to comment Share on other sites More sharing options...
jamesc Posted January 7, 2009 Author Report Share Posted January 7, 2009 What codes are set?? P0300, circuit default Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 7, 2009 Report Share Posted January 7, 2009 That is a misfire code. Check routing of your wires, check for vacuum leaks, check your coils to be sure they are firing. 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...
Ranger Posted January 8, 2009 Report Share Posted January 8, 2009 Check for a ripped plenum. On the 2000+ Northstars, the plenum is the rubber coupler between the TB and the manifold. They tend to split on the bottom where it cannot be seen and causes a vacuum leak. Spray some Brakleen or carb cleaner around the base and listen for an RPM increase. Link to comment Share on other sites More sharing options...
jamesc Posted January 9, 2009 Author Report Share Posted January 9, 2009 Check for a ripped plenum. On the 2000+ Northstars, the plenum is the rubber coupler between the TB and the manifold. They tend to split on the bottom where it cannot be seen and causes a vacuum leak. Spray some Brakleen or carb cleaner around the base and listen for an RPM increase. Thanks Ranger, I will do that. I recall having it replaced somewhere around 75K or so. That may be it, i will let you know. Have a great day. Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 9, 2009 Report Share Posted January 9, 2009 Ranger, not to dispute you, but in the past when that rubber plenum goes bad it creates a lean mixture and the following codes show up because of the unmetered air rushing in behind the TB. P0171 - Fuel Trim System Lean Bank 1 P0174 - Fuel Trim System Lean Bank 2 I was getting a P0300 when I did the upper intake manifolds in an 02 3.1 Chevy, but I did something wrong putting the intake manifold gasket in and it created a misfire on one or two cylinders possibly adjacent cylinders. I am leaning toward cracked porcelon on a plug, incorrect ignition wire routing, a bad coil or an injector problem. I would do a compression test on the engine first Test the coils for even strong output If those check out, I would look toward the injectors testing their resistance and listening to them with a scope to hear them working 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...
Ranger Posted January 10, 2009 Report Share Posted January 10, 2009 I agree on the lean codes Mike. I mentioned it because it is common and easy to test. Seems I have heard of it causing a rough idle, but not positive. Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 10, 2009 Report Share Posted January 10, 2009 I agree on the lean codes Mike. I mentioned it because it is common and easy to test. Seems I have heard of it causing a rough idle, but not positive. Understood, thanks 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...
Logan Posted January 11, 2009 Report Share Posted January 11, 2009 A leaking boot should create lean code. All the boots will go bad sooner or latter. One bummer on the Cadillacs is you will only get a po300. The system will not identify which cylinder has the miss fire. No spark plug wires on the 2000. Just coil banks. I suspect a bad coil bank. Kinda like the old GM HEI modules. Those who knew always carried a spare. I carry a spare coil bank in the trunk. 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...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.