i need some advice on coils and misfire codes.

[hillbilie5.0]

ok so my 2000 GT spd has had the check engine light on since i bought it. i got the car for real cheap and i know it has issues, but im like rebuilding/modding and the car runs good and strong. i scanned the car with the snap on modis and it gave me missfire codes in cylinders 1,2,3,4,5,6,7,8 i cant really feel any missfire while im driving, like i say the car runs great. so its a random missfire. i have replaced the fuel filter, the maf, the spark plugs and cleaned the entire intake, throttle body, iac ect. its all stock by the way. i clear the codes and drive the car and after 30 miles or so the light comes back on. if i scan it right away it will have codes for misfire in only one or two cylinders. i'll scan it the next day and there will be a few more and the next day or so it will be all 8. so im thinking i need to replace all 8 coils? it really isint that expensive. i can get 8 accel coils through Atech for 120 bucks or something. have any of you guys had these misfire problems? you think 8 coils will be the end of it? thanks

 

[wmburns]

Can you post the entire DTC code?

Note, it is not likely to have 8 coils go bad at the same time. More likely to have a common cause. Examples:
* Worn out spark plugs. Excessive gap (wear) or fouled.
* Moisture in the spark plugs wells.
* Bad COP boots from running with moisture in the wells (long shot).
* Poor crank shaft sensor (CKP) signal/cam (CMP) signal.
* bad engine ground.
* worn timing chains
* Fuel delivery/pressure problem.
* bad alternator rectifer diode.

Does the car have under drive pullies? This may cause a poor CKP signal. This is a common problem with the piggy back pullies.

OBTW, stick with Motorcraft COP's. They will give the best service for the $$.

The odds do not favor 8 new COP's being the end of it. PM me before you actually buy a set of Motorcraft's (unless you are looking for an excuse to put a fancy aftermarket COP on). However, if you want validation, buy one new COP. Install it. If it really is a bad COP, then the cylinder with the new COP will stop throwing DTC's.

 

[hillbilie5.0]

it does not have underdrives or anything, the intake is stock other than a k&n filter and the maf i replaced with a new stock one. the spark plugs are new and gapped correctly. i am not looking for an excuse to buy fancy coils i would rather not buy 8 coils i was just looking at the accels because they are inexpensive. i did replace a couple of the coils and if i remember right there was no codes in those cylinders for a couple days then they were back i think. that was a while ago and i dont excatly remember. on monday when i go to work i will scan the car and post the codes because i do not have them written down. does a bad alternator cause misfires like this often?

 

[wmburns]

It happens often enough that it should be tested for esp if the usual things are inconclusive.

Do you have a BIG sound system? The larger load can reduce the life of the alternator. What shape is your battery in? Are the terminals clean and tight? Remember a strong battery is needed to excite the alternator's field coil.

Consider that it is fairly easy to test the alternator. Any autoparts store can do it. Some can test more fully with the alternator off of the car. Suggest calling and asking.

Note: A professional shop would have the scan tools and O-scope that make it possible to perform a definitive analysis (power balance and time spectrum). Tools that are out of reach for the average home mechanic. This leaves the home mechanic to do basic functionality tests and trail/error.

Consider also, that a fair percentage of time, the problem is with the COP boot only. If the insulation is damaged, the spark can leak out causing a misfire. New boots are less $$ than the entire COP.