Bad Ignition Coil?
Thread Starter
Intermediate
Joined: Mar 2004
Posts: 33
Likes: 0
From: Peabody MA
Bad Ignition Coil?
So, I belive that one of my cylinders isn't firing... I've changed the plugs and tried a new wire and to no effect. One of my coils is a different shade of color, could be becuase of an oil spill but I'm not sure. How can I check to see if this is my problem or not?
TYIA-
Dan
TYIA-
Dan
Melting Slicks
Joined: Jun 2004
Posts: 3,439
Likes: 6
From: Newark, DE
St. Jude Donor '06
Originally Posted by CoRpSeMA
So, I belive that one of my cylinders isn't firing...
[. . .]
How can I check to see if this is my problem or not?
[. . .]
How can I check to see if this is my problem or not?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Dan
Check for codes!! The following web site will tell you how and what they mean.
http://www.stengel.net/diccodes.htm
I have to go to a Prince concert and when I get back I will post the procedure for checking the coil resistance and voltages. More than likley you have a BAD spark plug wire. Please check the resistance of each one with an ohm meter, Stock wires should read from 250 ohms to 750 ohms. If they are like in the MEGOHM range you found the problem
Let me know how you make out!
Bill C
Check for codes!! The following web site will tell you how and what they mean.
http://www.stengel.net/diccodes.htm
I have to go to a Prince concert and when I get back I will post the procedure for checking the coil resistance and voltages. More than likley you have a BAD spark plug wire. Please check the resistance of each one with an ohm meter, Stock wires should read from 250 ohms to 750 ohms. If they are like in the MEGOHM range you found the problem
Let me know how you make out!
Bill C
Tech Contributor
Joined: May 2003
Posts: 7,035
Likes: 134
From: North Augusta, SC
Someone posted a way to check the coil packs using a timing light a while back (evil-twin maybe?), but I can't find it with a search. Basically, clamp the timing light onto a plug wire and observe the pattern of the light, it won't be an accurate RPM indicator but will have a distinct pattern. Do that to all 8 wires, if a coil pack is bad it should have an obviously different pattern of flashes.
Good luck
Good luck
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Each wire "if connected to a timing light" should cause the light to FLASH. No special pattern or color, just a bright flash the should coinside with the firing of the coil. If the coil is producing high voltage the inductive pick up will sence the HV and cause the light to strobe. As the RPM picks up the flashes should increase in frequency byt will look kile they are dimmer than if at idle. This is normal!!
Just because the light flashes, it does NOT mean that the cylinder fired!!
The spark plug could be shorted or broken, the insulation could be torn or burnt abd the voltage could leak to somewhere besides the plug gap!
Here are come ignition coil facts:
Each coil is supplied 12 VDC from the Under Hood electrical Center via mini fuse # 16 (10amp fuse). The ground for the coil circuit is G-107 which is on the rear of the block (drivers side)
The coils have the following wires that provide the following signals:
a. brown = reference low
b. Pink = Ignition coil reference voltage 12 VDC from ignition switch.
c. ignition coil control voltages from PCM are various different colors for each coil pack.
Cyl 1 = Purple
Cyl 2 = Purple/white
Cyl 3 = LT Blue
Cyl 4 = Dk Green
Cyl 5 = Dk Green
Cyl 6 = Lt Blue
Cyl 7 = Red
Cyl 8 = Purple
Bill Curlee
Just because the light flashes, it does NOT mean that the cylinder fired!!
The spark plug could be shorted or broken, the insulation could be torn or burnt abd the voltage could leak to somewhere besides the plug gap!Here are come ignition coil facts:
Each coil is supplied 12 VDC from the Under Hood electrical Center via mini fuse # 16 (10amp fuse). The ground for the coil circuit is G-107 which is on the rear of the block (drivers side)
The coils have the following wires that provide the following signals:
a. brown = reference low
b. Pink = Ignition coil reference voltage 12 VDC from ignition switch.
c. ignition coil control voltages from PCM are various different colors for each coil pack.
Cyl 1 = Purple
Cyl 2 = Purple/white
Cyl 3 = LT Blue
Cyl 4 = Dk Green
Cyl 5 = Dk Green
Cyl 6 = Lt Blue
Cyl 7 = Red
Cyl 8 = Purple
Bill Curlee
Team Owner
Joined: Jul 2001
Posts: 21,391
Likes: 1,011
From: Various places in Southern California.
Checking the plug will confirm that a particular cylinder isn't firing. To make sure the problem is the coil and not something else, try switching the coil to another cylinder. Then if that cylinder stops firing, you know you've found the problem.
Sometimes you can tell if a cylinder isn't firing by checking the temp of each exhaust manifold right at the head, but this has to be done shortly after starting the car. This may save you some time.
Sometimes you can tell if a cylinder isn't firing by checking the temp of each exhaust manifold right at the head, but this has to be done shortly after starting the car. This may save you some time.
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