I finally got that 2005 P71 back to Illinois from Montana. I had a shop scan it and they said it was getting a misfire code and the cats were clogged. I neglected to ask what exact code was thrown. He said its probably the coils. I pulled them so I could bench test them. Any other likely thing that will cause a misfire? Anything specific to Crown Vics?
Anyone know how exactly to test these coils? I assume that you measure the resistance across the 2 pins or something like that.
As for the clogged cats, if I found someone selling a complete exhaust, what years are compatible with an 05? The one I found is from a 2000LX. If that is not a good idea, then what?
All I have to add is a bad coil can ohm out OK and actually be junk due to internal arcing BTDT.
The one time I did, it was snuck into the Ford engineering department in a box and came back to me with the results on it in paint pen. I think you can do it with a good oscilloscope http://www.underhoodservice.com/Article/96302/tech_tips_using_the_oscilloscope_ignition_coils.aspx
When they fail this way, they will usually miss under load, the more pedal you give it, the worse it will run.
Both codes can be caused by an exhaust leak. If none maybe all it needs is some good fuel cleaner and an Italian tune-up. Getting your own scanner makes things easier.
Kenny_McCormic wrote:
When they fail this way, they will usually miss under load, the more pedal you give it, the worse it will run.
This is exactly the symptom. Idles like a champ. Anything more than an 1/8th throttle, and it runs out of guts.
get scanner. read code. if misfire on a specific cylinder, swap coils to another one and run it. read code again and see if misfire followed the coil to the new cylinder.
Sounds like a plan. Any other ideas on the cats in addition to pjbgravely's?
You can test the cats for plugging with a vacuum gauge.
Raising the rpm should result in higher vacuum than idle.
How do I do that? Is there a port to plug in to?
Find the vacuum tree, unplug one that does something stupid and unimportant (HVAC, EVAP, the brake booster line if you have a proper reducer, etc.), plug in gauge.
I have had this problem on 2 different p71s. First time it showed a cylinder 3 misfire so I did all the coil swap stuff and it lead nowhere. I then changed the fuel filter and injector cleaner on the next 2 tanks. It actually ran great 5 minutes after the injector cleaner but I was being paranoid about it.
The next time it turned out to be a small bit of debris in the plug hole! I had pulled the coil pack and found this little piece of plastic(?) down by the plug.
Never found out where it came from but once I removed it the car ran fine!
