Hello all! First off Id like to say thank you for taking the time to read this and helping me out.

I have a 2003 f150 that has a history of misfiring on one side. It started with a misfire on #1, then #4, and finally #2. I replaced all 8 plugs last year and each COP as it gave the misfire code over the course of the last 3 years. My latest run in was with #2, and I replaced the COP today and took it for a test drive. It was running pretty rough at idle, which I assumed was from disconnecting the battery, but then the stuttering started but it felt a little different than the standard misfire that usually didnt pop up until 40-50mph. This stutter was more constant, and it also let up when I would coast. I only took it for a 4-6mile test drive and toward the end, the "Service Engine Soon" light started blinking and then went off by the time I got home. I parked it and noticed quite a lot of crackling noises that seemed more than normal, but it was a hot day and I was pissed that I didnt fix it so I cant say for certain if it was out of the norm or not, but it seemed louder and more frequent. Then I got to worrying about my cats going bad.
So, my questions are:
Could I have done something wrong when changing the COP?
What can the flashing "Service Engine Soon" light mean? Ive only seen a solid one before.
Should I be worried about the cat going bad since all the issues have been on that one side?
What should I do next?

Thank you all so very much, I greatly appreciate any help.

 

The flashing check engine light flashes when it detects a misfire, its basically telling you your missfiring, nothing to worry about, Im thinking vacuum leak at the intake or pcv valve at the back of the intake the pvc line goes in at a 90 degree angle and oil breaks it down over time. get a can of carb cleaner and with the engine at idle spray behind the intake and where the intake meets the head, if she smooths out you got a leak and that would cause a lean mixture to point of missfire, thats why its so random, go try and let me know

 

Wrong. A flashing MIL indicates a severe, catalyst-damaging misfire. You'd BETTER worry about it, cats are not cheap. Cats can also be damaged over the longer term by unresolved misfires or from running with other conditions that cause excessive fuel to be dumped into the exhaust.

Check the misfire counts in Mode $06 to see which cylinder(s) are misfiring in addition to whatever cylinder might have coded out.

You may well have a bad COP connector or wire adjacent to the connector or a connector that doesn't stay seated. It happens.

 

absolutely right. a flashing MIL means the catalytic converter is being damaged. it's best to get the misfire fixed. too much raw fuel being dumped in the converter causes it to heat up more and more. if it gets too hot/red it can potentially catch on fire.

check the basics first make sure all the coils and injectors are plugged in and that they lock. if they don't then get a new connector or try to put a zip tie on it to get it to stay. whenever I replace a coil I always replace the plug too. bad plugs can cause coils to go bad.

 

That just happened to mine a while back and I could smell something about half way home. I was told that in misfire condition that the cpu will shut off the injector also?? My CEL went out while coasting, came on on mild acceleration (flat terrain), and flashed while climbing hills. I think my cats are toast, although no new codes have registered in the computer since replacing the COP and SP.

 

Thank you, I will go check the connections again. I replaced all 8 plugs last year, which is why I just went with the COP. I didnt smell the sulfur/rotten egg smell from the cats and the light started flashing going up a hill not even 1/4 mile from home so Im just holding out hope that I didnt damage them. sigh.

 

Well. It pains me to say this, but sometimes you make stupid mistakes and learn from them so Im sharing this in hopes that maybe it would help someone else down the road.

I went back and checked all the connections and started wiggling the COP and it wiggled a bit down by the boot, but all the others were pretty stationary. I pulled it out and compared it to the oem that I was replacing and it was about 1/2 inch shorter than the oem, which I honestly just didnt even notice and it looks just like the other ones ive bought in the past. Needless to say, that pretty much explains the fuel getting into the cat. I took it back to Autozone and they said it was the right part and box number but somehow the wrong cop got put into the box. Go figure. They gave me the true correct part, same length as the oem I brought in to show them and I installed it and it runs like a champ.

So, my last question is, if its running perfect, how will I know if the cats were damaged during my 4mile test drive? Any advice is always appreciated.

 

I would take it for a ride, keep your eye open for check engine light, and maybe after a few miles you could connect your code reader and check for codes. If no codes are present, I would consider them okay. Someone more knowledgeable than I may have better advice.

Sent from Nexus 4. IB AutoGroup

 

I hope that falls true for mine. I drove 70 miles with this changing CEL light smelling something about half way back.

Q: If the cats are melted,will that restrict exhaust flow and burn the exhaust valves? Would a running pressure test before and after the cat on the exhaust pipe tell the story?

 

ok, Ill try that. Thanks again for everyone's help!

 

they should be ok if the CEL was only flashing for just a little while. clear the codes and drive it. it will usually take 2 drive cycles to see if the CEL comes back on. good luck