moralwarfare Posted November 1, 2009 Report Share Posted November 1, 2009 Hello everyone! I've got a customer with a 2002 Seville STS, northstar powered. It was leaking coolant severely from the head gaskets, and I installed a used engine in the vehicle as opposed to replacing the gaskets. Everything went pretty smoothly, except after it ran for a while I got a (flashing) CEL and P0300 random misfire code. I have searched the forums, but am not convinced of an answer. When accelerating from a stop, the vehicle sputters slightly, then smooths out in the mid to upper rpm range. I wound up swapping the coil packs and wire boots from the known good engine (one removed) to the currently installed engine. It has new spark plugs. I then cleared the light and the issue improved, only to return some 30 miles later. I checked for obvious sources of vacuum leaks, but have found none. Any issues you guys know of that may cause this? I can answer any more questions to clarify. Thank you. -joe. Link to comment Share on other sites More sharing options...
Ranger Posted November 1, 2009 Report Share Posted November 1, 2009 Hello everyone! I've got a customer with a 2002 Seville STS, northstar powered. It was leaking coolant severely from the head gaskets, and I installed a used engine in the vehicle as opposed to replacing the gaskets. Everything went pretty smoothly, except after it ran for a while I got a (flashing) CEL and P0300 random misfire code. I have searched the forums, but am not convinced of an answer. When accelerating from a stop, the vehicle sputters slightly, then smooths out in the mid to upper rpm range. I wound up swapping the coil packs and wire boots from the known good engine (one removed) to the currently installed engine. It has new spark plugs. I then cleared the light and the issue improved, only to return some 30 miles later. I checked for obvious sources of vacuum leaks, but have found none. Any issues you guys know of that may cause this? I can answer any more questions to clarify. Thank you. -joe. Did that include the "plenum"? On the 2000+ Northstar the "plenum" is the rubber coupler between the TB and the manifold. They tend to rip on the bottom where it can't be seen. Link to comment Share on other sites More sharing options...
moralwarfare Posted November 1, 2009 Author Report Share Posted November 1, 2009 I did read about that and need to go back and check the boot, but I did swap it from the known good engine and did not see any cracks or splits at the time. Link to comment Share on other sites More sharing options...
BodybyFisher Posted November 1, 2009 Report Share Posted November 1, 2009 One of the signs of a bad head gasket is a misfire. Put a Tech2 or reader capable of 'seeing' misfire history or real time misfires and see what cylinders are misfiring. Look at the plugs for moisture or evidence of coolant being burned 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...
bigmoparjeff Posted November 2, 2009 Report Share Posted November 2, 2009 If the "new" engine was sitting around in storage for many years, you may have a problem with one or more fuel injectors. In March 2008 I bought an engine for a Dodge Neon from a local junkyard. The engine only had 17K miles on it becuase it was out of a car that was wrecked back in 2001-02. It was then removed and stuffed into a warehouse, where it sat until I bought it. I had a real hard time getting it to start, then when it did, it ran terrible. I eventually figured out that the injectors were destroyed by our modern, caustic fuel. If you didn't swap intakes and injectors, you could have a similar problem, just not as severe. If your engine is out of a fresh kill, I would go with the following: When in doubt, run a compression test. Jeff Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.