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I have a 2002 Expedition with a 4.6L. Last week the CEL came on and it started to run rough. When I connect my code reader it does not come on and I can get no codes. The code reader will work on mt 2005 GMC. It haso also worked on the Expedition in the past. Does this indicate I may have a connector problem with the connector? I plan to go to Autozone and see if they can read any codes tomorrow. Is the DTC fused or something? THANKS for any ideas.
Thanks for the quick reply. You are correct, hte fuse was burnt. I swapped out the fues and I can now read the code. I have a miss fire on cylinder #4. I had this problen in the past and cleared it by changing out the COP boots. I hope it is that cheep this time. Thanks again.
Have to given thought as to a possibly bad injector? Your best bet to avoid spending for wrong parts is to swap the COP, plug, and injector, one each to another cylinder (each to a different cylinder). When the misfire code moves from #4 to one of the other cylinders, you've found the bad component. Make sure you write down which of the three components went to which cylinder.
I would not switch all of them around. IMO, #4 Coil is the hardest one to get to, but I would switch #3 and #4. Also, I would never change just 1 plug on my Expy. If you are anywhere near 100,000 miles, I would change all of the plugs. Then, if you really wanted to, you could switch the boots around. I use Autolite Double Platinum plugs. I think APP103. They must be DOUBLE PLATINUM or OEM Motorocraft plugs. Also, use dielectric grease inside the boots and on the actual electrical plugin. Be generous!
Use anti-seize on the plug threads and there is a trick to getting the plugs in. Use 2 spark plug sockets. 1 with the rubber insert, 1 without. Place the plug in the socket just enough for the rubber to grip it, then start the threads. Get about 3 turns on it, and then use the socket without the rubber insert to finish the job. I found that doing it this way makes the job easier.