Sevenfold Posted February 15, 2014 Report Share Posted February 15, 2014 Sometimes my 1991 Cadillac deVille 4,5 starts and can run for 5 minutes and then it just dies n doesnt start again. Runs smooth when it runs with no missfires or so. sometimes it start the day after like nothing has happend an runs maybe 20 minutes when its dead all eight sparkplug has a spark but on the wrong spot...like half a lap wrong cranksensor or ECU problem? Link to comment Share on other sites More sharing options...
Cadillac Jim Posted February 15, 2014 Report Share Posted February 15, 2014 You should check for OBD codes. They may tell you what is wrong. I wouldn't start buying parts until you have a better idea what is happening. I have heard of clogged catalytic converters or mufflers that cause this problem. One of the reasons that you see humongous tailpipe openings in school buses is so that the kids can't jam a potato on them like they once did, which would cause the school bus to stall a few blocks later. Once you have determined that the exhaust is OK, there are three things to check: gas, spark, and compression. The best time to check is when the engine stalls. Smell the exhaust and, if it smells of gas, your problem is likely the spark. If it smells hot but not strongly of engine exhaust, your mixture may be too lean, e.g. not enough gas. If the engine spins too easily when you are trying to restart, there may be a compression problem, or the throttle may be closed. Given that information, we can look farther. I'm not knowledgeable about problems specific to the 4.5 liter, so others will likely chip in here. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
KHE Posted February 17, 2014 Report Share Posted February 17, 2014 when its dead all eight sparkplug has a spark but on the wrong spot...like half a lap wrong Please clarify this. How can the spark be at the wrong spot? Are you referring to the actual spark on the plug itself or some sort of timing issue? Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Cadillac Jim Posted February 18, 2014 Report Share Posted February 18, 2014 I think that he is saying that the spark is firing near BDC, not TDC. If so, there probably is a problem in the distributor. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
adallak Posted February 22, 2014 Report Share Posted February 22, 2014 Sevenfold, Your engine is 4.9 not 4.5. Welcome to caddyinfo.com! The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Logan Posted February 22, 2014 Report Share Posted February 22, 2014 At that age...could be anything.. Couple of common ones.. Be sure to inspect the large battery ground mounted on the engine block near the starter. I would also inspect the AC pickup coil and ignition module wires inside the distributor for turning green. See attached picture. 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...
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