Gremlin engine miss

[84convertablegt]

OK, heres the deal. this is concerning my 2000 crown vic p/i. it has the 4.6 with coil on plug ignition. When i bought the car, the check engine light was on. i read the codes. its was engine miss in cylinder 4 detected. and it felt like cylinder 4 wasnt even working as far as power goes. so i changed all the plugs and the coil on cylinder 4. the problem went away and the check engine light went off. then 2 weeks later (NOW) the car starts missing again and the computer says cylinder no. 2 miss detected. i tested the coil and it was a little out of spec, so i replaced it (this is getting expensive). the problem seems so have went away, but what would be causing this? i cant tell if its really the coils or the plugs. i used bosch platinum plugs for replacements. also, i originally though that i had a small coolant leak from the radiator hose that goes into the intake from the firewall because there was a little coolant there. i figured that would explain why cylinder 4 was fouled up. so i replaced it and used new clamps and all seems well there. this is my first 4.6, so im not too familiar with common problems, etc. any help would be appreciated.

 

[triggz]

Does it miss more on cold start? Have you done a compression test? What did the plug look like that came out of #4?


FWIW, My car never liked bosch platinums, or anything really besides autolite coppers.

 

[84convertablegt]

well all the plugs looked bad. but this was a former police car and had been run rough for its 92000 miles. The plug looked like it still could have fired though. this may not be the best idea, but i did replace the number 2 cylinder plug with a autolite platinum instead of a bosch. i figure mis matching one plug as a control wont hurt anything. and it doesnt matter if its cold or hot, same deal. is there anyway a cracked intake(water wise) could cause this. i know the 4.6's had some issued with water leaks but i figure that would be apparent i.e. water running out of the back etc.

 

[triggz]

Yes a cracked intake could definitely lead to all sorts of weird running problems. The cracking intakes were fixed for mustangs in 99, don't know about crown vics though

You should be able to smell antifreeze on the plugs or in the cylinders if its cracked enough to cause a miss.

Any other issues with the car that could relate? Clean coolant in the tank, clean oil?

 

[84convertablegt]

ok, heres the deal with fluids. there was aliitle antifreeze on the number 4 cylinder plug, but i believe it was from the leaky heater hose i had running down the hole from the top. that has since disapeared after replacing the heater hose and plug. the oil is clean, no milkyness at all and smells like oil. the antifreeze is kinda dirty, but not bad. it still looks green, definately doesnt look like a head gasket type thing or anything. thats why this is so confusing. im hoping its something simple, would multiple coils tend to fail at the same time and only around 100 miles or less? theres not much else besides the coil and pcm to control spark. no ignition box on these cars. any more idears!

 

[84convertablegt]

totally unrelated, but ive been putting off changing the fuel filter, that could cause a miss maybe, or not? i dont know the last time it was changed.

 

[84convertablegt]

totally unrelated, but ive been putting off changing the fuel filter, that could cause a miss maybe, or not? i dont know the last time it was changed.

anyone?

 

[DBMSTNG]

don't use platinum plugs other than if they are OEM. they tend to run hotter and for some reason sometimes cause problems. but that's probably not your problem.

Ford has redesigned the coil on plugs about 15 times. no joke. the reason is because they tend to crap out for no reason. so far i've been lucky with my 99 GT.

 

[Superhereaux]

totally unrelated, but ive been putting off changing the fuel filter, that could cause a miss maybe, or not? i dont know the last time it was changed.

a fuel filter won't cause a miss on a specific cyl. but it wouldn't hurt to change it. you can usually tell by the amount of grime on it how recently it's been replaced. if you can still see the original color, good. if it's solid black with build up, not good


i'd get those bosches out of there, copper plugs aren't too expensive

and if you get anymore misfires, swap the coil and see if the misfire follows.
same with the plugs

 

[84convertablegt]

i'd get those bosches out of there, copper plugs aren't too expensive

and if you get anymore misfires, swap the coil and see if the misfire follows.
same with the plugs

Well the reason i bought the platinum plugs was because o.e. was platinum. but the bosch's are obviously a little different. like i said i replaced the one with a autolite platinum which is the same thing as a motorcraft o.e. platinum, so i will probably end up going with those before too long. but what is everyone else using. will a straight copper plug work ok?