Testing Coils (COP) with a volt meter?

J

J

OCCUPY LoD :)
Ok, I'm at my wits end, seriously. I'm pretty smart when it comes to driveability stuff but only in the "street smarts" sense. When it comes to electronics and stuff, I was never really taught how to diagnose these issues or never learned properly.

So, I'm trying to get down to the bottom of my misfire issues on the Evergreen. When I bought the car, it had P0305/P0306 codes. I swapped the COP/boots from 5/6 to 7/8 cylinders. Misfire stayed on #6 cylinder. Installed a new plug, still there. Drove it 3 hours home from Sacramento.

Now, I've swapped the 5/6 injectors...still P0306 and now a P0308 code. :( I had bought 8 Autolight 764's so I just replaced all the plugs with a .54 gap (the old ones had carbon burns and were gapped at .42).

I ripped apart the harness on the left bank and it looked good, no brittle insulation or exposed wires.

So, I went online to my AllData account and started going through their diagnosis process. They were telling me to test the coils using an ohm meter by touching the coil pin Coil Driver to the coil spring. First...I can't for the life of me find out what a Coil Driver is and where it is on the coil. Second...I used my ohm meter and touched ever type of combination on 9 of the 16 coils I have here and did not get the same readings. Obviously I'm doing something wrong so I'm in much needed help. I shouldn't have to pay someone else to do what I should be capable of doing.

Here is the diagnosis process so far....I'm stuck on JF2.

HD1-NO
HD2-Does Not Apply
HD3-Yes, P0442 (I think) Small EVAP system lean (Probable Cause is Fuel Cap)
HD4- NO...went to JP1

JP1-YES...new plus, swapped coils/boots and even installed different coils that I got from Erik (only on 6/8)
JP2- Tested the coil(s) every way I could think off and got no reading close to 4k-10k. I'm using a craftsman meter similar to this one (has same functions, different layout).

HD1.gif

HD4.gif

JF1.gif

JF3.gif


PLEASE HELP! :confused:
 
The coil spring is the part that contacts/connects to the spark plug. There are two terminals on the coil -- one goes to B+ (bat) and the other goes to a driver transistor.

The coil is built as a center tapped transformer winding. The B+ wire is in the "center" of the coil. The CD terminal is the bottom of the coil. The top of the coil is the spark plug connection. There must be resistance between all three "terminals".

Electricity flows through the center wire to the driver to ground. When it is time to spark, the current is turned off. The collapsing magnetic field generates the high voltage spark at the spark plug end.

If this is TMI, I apologize in advance.
 
I think its basically going through all the failure points of a coil... it starts with the coil itself, and then it layers on the "spring" that runs through the coil boot. The tests would outline what exactly failed within the coil if that was in-fact the issue.

You've already figured out that its not the coil itself though, I think you should see what kind of voltage is supposed to go to coil#6 as well as measure the resistance in that wire.

That is outlined in JF4
 
I agree with Max.... you installed a known good coil. Time to move on. (Is it possible that you didn't have the meter set at 20K Ohms?) I pulled one of the coils you sent me and I got the correct reading per JF2 with a Radio Shack digital multimeter.
 
HOTLNC said:
If this is TMI, I apologize in advance.
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Nope, I understand. And that's what I was testing...but EVERY coil I tested did not give me a reading when I touched the B+ or the other pin to the coil spring pin. How do I know if I'm doing it right if I can't get a reading??

maxmk8 said:
You've already figured out that its not the coil itself though, I think you should see what kind of voltage is supposed to go to coil#6
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Totally Max...but I'm still stuck on JP2...because, if I can't measure the coil resistance right, how the heck am I going to measure the resistance on the harness!!??

budpytko said:
I got the correct reading per JF2 with a Radio Shack digital multimeter.
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So...tell me how you did it, because I'm doing something wrong. When I switch it to ohms (200) and touch the two test wands together I get .004 ish. When I touch B+ to the other terminal I get 1.4ish. When I touch either terminal to the spring or the driver I get nada.

95blklsc said:
If you rule out the coils and can't figure it out you just might need something like this lol ;)

http://cgi.ebay.com/ws/eBayISAPI.dl...8682&ssPageName=STRK:MESELX:IT#ht_1404wt_1141
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All fine and dandy...but we're still at square one, WTF does it mean and how do I measure ohms!?

Joeb6812 said:
Compression test? I hate to say it. :eek:
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I have one...but I was ruling it out because it's intermittant AND it goes away the more throttle I give it. In my head I'm thinking a harness breakdown but when I demand more power, the power is able to get through the harness because the engine is supplying more and its "jumping the gap", or atleast that's what I'm visualizing. If it was a spark related issue (bad boot/plug/etc) the more throttle I gave it, the worse off the misfire.

95blklsc said:
I was thinking that too, but its a good idea to rule out electrical. Have you checked the injector? It could be stuck open pouring fuel into the cylinder. That would probably cause a misfire.
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I swapped injectors....I wrote that above. Swapped 5 for 6.
 
Just to cover basics again:

Common Problems That Trigger the P0306

* Worn out spark plugs, ignition wires, coil(s)
* Incorrect ignition timing
* Vacuum leak(s)
* Low or weak fuel pressure
* Improperly functioning EGR system
* Defective Mass Air Flow Sensor
* Defective Crankshaft and/or Camshaft Sensor
* Defective Throttle Position Sensor
* Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems
 
Have you tried using a different METER??? Also, when you touch the two leads together, does it measure 0 ohms? If not, there should be an adjustment to let you zero it out.

Replace the meter battery (s). I was using the 20K ohm scale.

BTW, it isn't a volt-meter, it's a multimeter.
 
Obviously two different animals but, my mothers PT cruiser turbo had an intermittent cylinder misfire where it would miss at idle and run just fine at higher rpm's. Turned out it was a burned valve after the dealer went and replaced everything under the sun including ignition stuff, injectors, and the pcm.
 
Well Joe, hate to say it but you were right. I was hoping for the best....but I guess I should have saw the signs when I bought it. Someone had already replaced the spark plug and coil on ONLY that cylinder and it was still misfiring. So much for getting it SMOG'd.

Tested 5-8, #5 150, #6 90 (even after 6 cycles vs. 3), #'s 7/8 120.
8c2e0e49.jpg

:(:(:(:(:(:(:(:(:(:(:(
 
****........ did you try to squirt some oil in? I remember reading if the pressure comes up with some oil in there it can indicate that the rings are letting significant pressure by, if not it could be a bad valve seat. If its a bad valve seat it would probably be better news since you can service just that head. Might be worth looking into a junkyard motor... :(
 
Wanna sell it ? ;)

I kind of expected that, but I have been dealing with ****ty cop coils for a while now, and finally pin pointed which one was causing a miss which felt like trans shudder. Of course no codes.
 
Mad1stGen said:
Wanna sell it ? ;)

I kind of expected that, but I have been dealing with ****ty cop coils for a while now, and finally pin pointed which one was causing a miss which felt like trans shudder. Of course no codes.
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Yep I had that one happen on my crown vic too... thankfully you can get a set for $80 on flea-bay... Chinese but I don't care on a 255k miles crown vic.
 
So, just tried to smog the evergreen anyways and it passed. Cleared the codes and drove it to set the readiness monitors and blamo. All set. Haha! Drive it till it dies.
 
J said:
So, just tried to smog the evergreen anyways and it passed. Cleared the codes and drove it to set the readiness monitors and blamo. All set. Haha! Drive it till it dies.
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Good thing it passed.....now it just has to pass again... ;)
 
Mad1stGen said:
hahaha ... I am glad I wasn't the only one seeing thru this :eek:

j/p :wave:
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from what I hear pullied is all set and passed smog like a champ....pretty impressive when you think about it....but that is unrelated to this thread. Sorry for derailing ;)
 
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