Hey my dads 97 F150 5.4 is running like crap, and im wondering if one or more of his coil packs has gone bad. Problem is I have no idea how to diagnosis these things, ive only had experience with distributor ignitions. Im gonna go out and take a look at the plugs now, but if anyone could tell me how to test his coil packs, that would be great!

 

Get the codes read, could be something other than a bad cop.

 

+1 on codes.........the first thing to do when diagnosing is check the codes. on my ranger I have a misfire on cyl 3 that i am chasing but my cel does not come on. When the truck is running bad check for codes. sometimes they are pending and then they go away before the cel comes on. I got my codekey code reader at costcos for $20......priceless.........


and I dont know how to test the cops i imagine you could us a mm and check ressitance

 

[quote=powersmoked;8788702
and I dont know how to test the cops i imagine you could us a mm and check ressitance[/quote]

It's my understanding that if you have the right equipment you can "stress test" a cop off the vehicle, but I don't think even that is a 100% sure test.

 

Sorry, forgot to mention that I did get the codes read, and it was for lean mix on both cyl banks.

And as far as this problem goes, I found why its running bad. The line from the PCV valve to the back of the intake had rotted away and busted open. MAJOR vacuum leak.

But I would still like to know how to tell if a coil pack is good or bad...

 

if you get a code that says #3 cylinder is misfire, the normal test is to change out #1 and #3 and see if the error code moves to the new cylinder.-------- bad vacuum hose would cause your leak code.

 

Throw an ohmmeter on it, open=bad.

Haynes lists the Primary resistance (across the connector terminals) should be .55 ohms, Secondary 5,500 ohms (between + and the plug spring/wire).

Jamie

 

Coils are a difficult issue to pin down except for an outright hard failure where a code would be set and there is no mistery about it..
Resistance testing has little value if you "don't find" either the primary or primary to secondary open.
A miss, surge or intermittant miss is often a coil with shorted turns or even an intemittant 'open' that can be temperature sensitive. Could even be a bad boot or a pushed spring stuck up in the boot..
One way to get a lead on which bank the faulty coil/cylinder is on, is to use a good scanner with the ability to record live date and able to trigger on a fault detection.
Often you will see the Long Term Fuel Trim on one bank noteably out of line with the other bank.
This can be the OX sensor detecting excess air being passed by the missing cylinder that alters the L.T.F.T. table % for that bank.
Saw this many times in my testing for such issues.
A simple reader will not be able to do the data recording.
Looking deeper into the PCM operating areas (PIDS) is the way to see what is happening before any code is set, often will provied the lead.
When a code is set then you don't need anything but a reader.
These better scanners cost more than $50 but are worth the money to learn and be able to handle your own diagnostics with some help by learning how the FI system works for Ford. (go to the Motorcraft site and down load the overview) about 120 pages.
Good luck.

 

I would replace them all. I fought changing Coils one by one for 2 years. I even bought a code reader. I would not get a failure recorded on any coils. I blamed the Transmillion the fuel filter and the intument cluster after the Instrumentation went haywire. The truck died one day and after being towed to repair shop it started right up. The COP was driving the computer nuts. If one goes the others are close. After replacing all the cops I haven't had a problem in 3 years and 40,000 mi. Runs like a dream (engine).

 

thanks for all the replys guys! After fixing the massive vac leak the truck runs like normal again, I think im just gonna replace the plugs and call it a day.