Running rough but no CELs
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Joined: Jun 2014
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From: Ponchatoula, LA
Running rough but no CELs
Repost from Expedition section, I figured it will probably get more views here..
Hey guys, I recently inherited a 99 Expedition 5.4 with 90k miles. I'm trying to fix it up so I can sell it. Like the title states, the truck runs rough but there's no check engine light on. I did some research and ended up replacing the PCV elbow and that made it run better for a while but now it's back like it was. It won't die, just a really rough idle and a miss while driving. I imagine it's probably a (or a few) coil pack(s), but I have no way of knowing which one(s) to replace. I would think that would illuminate a CEL though. I'm also having problems with the AC. Upon inspection, I found that the compressor clutch assembly was completely gone from the front of the compressor. I replaced the whole clutch assembly, then voided the system of Freon and refilled it to spec, still no cold air. The compressor clicks on and off like it's low on Freon but it can't be. I'd just sell it as is but in south Louisiana a working AC is a huge selling point! Any insight would be appreciated. Thanks in advance!
Hey guys, I recently inherited a 99 Expedition 5.4 with 90k miles. I'm trying to fix it up so I can sell it. Like the title states, the truck runs rough but there's no check engine light on. I did some research and ended up replacing the PCV elbow and that made it run better for a while but now it's back like it was. It won't die, just a really rough idle and a miss while driving. I imagine it's probably a (or a few) coil pack(s), but I have no way of knowing which one(s) to replace. I would think that would illuminate a CEL though. I'm also having problems with the AC. Upon inspection, I found that the compressor clutch assembly was completely gone from the front of the compressor. I replaced the whole clutch assembly, then voided the system of Freon and refilled it to spec, still no cold air. The compressor clicks on and off like it's low on Freon but it can't be. I'd just sell it as is but in south Louisiana a working AC is a huge selling point! Any insight would be appreciated. Thanks in advance!
Lead Driver
Joined: Sep 2006
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For the misfire, you need to use a Scanner to look at stored misfire data to see which cylinder/s have high counts out of monitor limits.
These monitors store misfire counts and are seen long before a code or CEL comes on.
If you were to see a code or CEL you would not be wondering which one was the problem.
The reason you don't get a CEL is the misfire clears, the count is not high enough to set a code/CEL.
This is indicating the fault is not a hard permanent fault but comes and goes with driving conditions and possibly temperature related.
The Scanner will tell you which one it is.
On A/C, you just need to know more about what to do on the system and there may be a large enough leak.
Good luck.
These monitors store misfire counts and are seen long before a code or CEL comes on.
If you were to see a code or CEL you would not be wondering which one was the problem.
The reason you don't get a CEL is the misfire clears, the count is not high enough to set a code/CEL.
This is indicating the fault is not a hard permanent fault but comes and goes with driving conditions and possibly temperature related.
The Scanner will tell you which one it is.
On A/C, you just need to know more about what to do on the system and there may be a large enough leak.
Good luck.
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