ETS Posted May 16, 2012 Share Posted May 16, 2012 2006 F250 5.4 4x4 Auto. I have a puzzler here. First off it has miss for first 30 seconds of operation every morning. Has 30k on Ford Reman. Longblock. 353k on body. Sets PO353 probably ounce a month. Replaced #3 coil and plug. Sets again switched coils and plugs with #1. Sets again. [Problem goes away for month after replacing/switching] Plugs look normal. Tough to run tests in a minute but has issue with #3 contribution. I have ohmed circuit back to PCM and looked for chafeing. No problems found. Question is can Fuel/Mechanical problem set Primary circuit fault? This truck has never had injectors done. Injector Leaking?? Going to test more Sat when I can pull it from service. P.S. also found PO300 this time. Fuel pressure and volume are good. Quote Link to comment Share on other sites More sharing options...
wring09 Posted May 17, 2012 Share Posted May 17, 2012 You have a bad PCM ...becoming pretty common these days..if youve replaced coil and plug and circuitry has no issues...then you have a bad driver in the PCM Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted May 17, 2012 Share Posted May 17, 2012 Fuel/mechanical issues will not set primary ign. fault codes. The best way to check the circuitry is to use an led test light. The light will be green when grounded and red when powered. All you have to do is back probe the number 3 coil and start it up. If the ground side is switching rapidly from red to green then the PCM is driving! I would not condemn the PCM until you have verified this. In most cases it is the actual connection at the coil. Check for pins being spread and close them up tighter and put a dab of electrical grease in there. Here is a article on this very issue. http://www.forddoctorsdts.com/forums/ubbthreads.php?ubb=showflat&Number=40179#Post40179 Quote Link to comment Share on other sites More sharing options...
ETS Posted May 17, 2012 Author Share Posted May 17, 2012 I thought that was the case but wanted to be sure. I remembered seeing your post on testing coil circuits but was unable to find it in search. I have checked connector and insulated it with dielectric grease previously. I will do a closer inspection and test circuit as per post. Haven't had a bad PCM here yet. 8 06 F250's in my fleet. Thanks Again Mr Clayton. Quote Link to comment Share on other sites More sharing options...
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