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Old 02-18-2007, 04:25   #1 (permalink)
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Crown Vic Engine Misfire

Okay, I will try and describe the problem that I am having to the best of my ability. I have a 2000 Crown Vic P71. A while back the engine started missing. The "idiot light" came on and I had the guy at the zone run the code tester on it. It came up "cylider 4 misfire" so I replaced all 8 of the plugs and coils. The damn thing was still missing so I thought maybe it wasn't getting enough fuel so I replaced the fuel filter (i did the air filter and pcv valve that day too) and it was still missing. I thought maybe a clogged injector. I ran injection cleaner through the fuel several different times. . . nothing. I have put seafoam through it, nothing. I have checked for vacuum leaks and found none. The "idiot light" came on again yesterday so I went down to the zone again and this time it was "cylider 7 misfire". The engine sounds just fine, but when I drive it (especially during slow accelerations) it is clearly missing. I used to get about 300 miles to a full tank, now I am lucky to get 230. I am really stumped on this one and I am not sure what else to check. It may be something easy that I have been overlooking. Does anybody have any suggestions?
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Old 02-19-2007, 11:14   #2 (permalink)
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Re: Crown Vic Engine Misfire

Well I have a few ideas. Did you keep the COPs in the same order when you changed out the plugs? Maybe the bad COP from #8 ended up on #7? I would recheck plug torque, put lots of dielectric grease on all the connectors for the COPs and make sure the connectors are all tight. One of mine is held on by a zip-tie cuz the connector is broken and w/o it the damn thing misses sometimes.
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Old 02-19-2007, 11:52   #3 (permalink)
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Re: Crown Vic Engine Misfire

At the time when I replaced all the spark plugs, I also put on 8 new coils ($$$). Believe me, we greased the hell out of them. Not only where the coil comes into contact with the plug, but also where the rubber boot connects to the plastic piece because I had issues with moisture getting in there previously.

Off topic: It's ironic that you are from Michigan because my P71 came from a MSP auction.
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Old 02-19-2007, 14:58   #4 (permalink)
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Re: Crown Vic Engine Misfire

OUCH! 8 new coils cost as much as the car. My p71 is a MSP unit too. Have you tried cleaning the MAF and EGR sensors yet? That made mine run a lot better...
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Old 02-19-2007, 15:59   #5 (permalink)
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Re: Crown Vic Engine Misfire

Actually, thats one thing I have never done. Where are they located at specifically? I am not really too familiar with this 4.8L engine to be honest. I think the MAF sensor is right up near the air intake, but I am not sure. I have more experience with the older ford motors like the 2.9L found in the Ranger and Bronco II. When I got this car, I was in way over my head.

Also, what type of cleaner do you recommend that I use? Most of the time I just clean these type of parts in some gasoline.
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Old 02-19-2007, 21:40   #6 (permalink)
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Re: Crown Vic Engine Misfire

4.6 sorry
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Old 02-20-2007, 04:51   #7 (permalink)
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Re: Crown Vic Engine Misfire

Well you are right about the MAF, its inline between the airbox and the throttle body, but closer to the airbox. The EGR is attached to the back of the throttle body with 4 screws. Also blow out the egr passages (extra lines coming off of the intake tube) with air as they can become clogged. Use electronic parts cleaner. Anything else will ruin the MAF I think.
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Old 02-21-2007, 19:46   #8 (permalink)
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Re: Crown Vic Engine Misfire

We took off the MAF and blew it with some compressed air. I was affraid to really do too much with the EGR because I know how expensive they are to replace, maybe the whole thing is bad, but I would have expected to get computer codes if it was.

I am starting to think there is something wrong with the vacuum system after all. Me and a friend of mine took the vacuum lines off one by one and examined them, but couldnt find anything. We put everything back together and the car is still experiencing the same misfiring.

I know it is losing preasure because after I turn the car off the heater vent doesnt close like it is supposed to, and then when I turn the car back on I hear it slam shut under the dash and it never used to do that.
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Old 02-22-2007, 15:02   #9 (permalink)
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Re: Crown Vic Engine Misfire

Some new info to shed on the situation. I got ahold of the mechanic I sent the car to last time and I discovered the idiot put carb cleaner in through the intake in an attempt to "remove carbon" from the throttle body. This was shortly after I replaced the plugs and coils the last time.

I spoke with a friend of mine today and he said that putting carb cleaner in the air intake more than likely "fouled out" one or more of the plugs and by replacing the spark plugs (again) it should take care of the misfiring. He then said if it persists, to look into replacing the EGR and/or MAP sensors.

Any ideas or comments before I go down to the zone (again) and spend more $$$.
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Old 02-23-2007, 08:43   #10 (permalink)
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Re: Crown Vic Engine Misfire

Well the carb cleaner is not OK for the coating on your tb. I'm not sure if it would foul your plugs or not but that can be easily checked before you run out and get new plugs. You are correct that the EGR is easy to mess up, but they are actually not too much to replace. They don't always give you a code, though.

I check for vacuum leaks with a bottle of starting fluid or carb/tb cleaner. I just spray it anywhere I want to check. This has helped me solve more than one unknown problem.
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