Author Topic: Good Coil Pack Not Firing  (Read 9269 times)

thunderpanda

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Good Coil Pack Not Firing
« on: November 15, 2010, 04:34:31 PM »
I have a '98 bonneville ssei, and one of the coil packs is not firing at all. I have tested every coil post by plugging a spark plug into it and running the car. 4 of them fire every single time, 2 fire very very infrequently or not at all, and they are on the same pack. I have tried replacing the coil pack, doesn't make a difference. How should I go about troubleshooting this? From my research I have determined that is most likely a loose connection, bad wire somewhere, or bad ICM but I don't really know how to go about figuring it out. Any help would be appreciated. Thanks!

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conniecartech

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Re: Good Coil Pack Not Firing
« Reply #1 on: November 15, 2010, 05:13:39 PM »
is the check engine lite on?

even tho u replaced the coil, did u try swapping it with one of the good ones to see if the problem 'moves' to diffrent cylinders with the coil? how about swapping plugs and wires?

another thing u can do is disconnect the wiring connector from the module and make sure the terminals are in good shape and making good contact. check the connector for loose or backed out terminals. follow the wires back as far as u can and check for breaks, wore off insulation, etc.

the problem with these modules is that there aint a good way to test them without special equipment. usualy what we do is eliminate evrything else, and replace the module if all else fails.

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thunderpanda

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Re: Good Coil Pack Not Firing
« Reply #2 on: November 15, 2010, 05:23:08 PM »
Quote from: "conniecartech"
is the check engine lite on?

even tho u replaced the coil, did u try swapping it with one of the good ones to see if the problem 'moves' to diffrent cylinders with the coil? how about swapping plugs and wires?

another thing u can do is disconnect the wiring connector from the module and make sure the terminals are in good shape and making good contact. check the connector for loose or backed out terminals. follow the wires back as far as u can and check for breaks, wore off insulation, etc.

the problem with these modules is that there aint a good way to test them without special equipment. usualy what we do is eliminate evrything else, and replace the module if all else fails.
 

Ya the engine light is on, I have a reader and it has confirmed cylinders are misfiring. Obviously since there is no spark they are not firing.

My method of testing each coil/post was using the same spark plug wire plugged into the same post, so that everything is the same except which post I am using. The problem does not move, it is definitely just the one coil pack. I did try with a couple different wires and plugs, always the same results. It fires every time one 4 of the posts, not at all on the 2 bad ones.

I took a quick look at the big connector for all the coils by disconnecting it... I didn't notice anything obviously wrong. I followed the wires as far back as I could.. It looks like smoeone of them go to the computer which I assume is the signal to spark, and one that went down to the bottom of the car and plugged into something, which I think might be the ground? I would bet there is a chance something is bad there, because we recently did work in that area and something could have been damaged or not plugged in all the way.

I couldn't really see anything on the ICM (Which I assume is the big computer thing that a whole bunch of wires plug into... and I think is what you mean when you say 'module'?), because I took the cover off it but all the actual connections are inside of it. And hopefully it didn't go bad because I think that is expensive to fix... though maybe I would just grab a junkyard one

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conniecartech

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Re: Good Coil Pack Not Firing
« Reply #3 on: November 15, 2010, 05:46:13 PM »
well, first lets get our jargon on the same page.  Shocked  id go with the icm. unless u wanna take it to a competant shop and get it checked out.

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thunderpanda

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Re: Good Coil Pack Not Firing
« Reply #4 on: November 15, 2010, 06:12:24 PM »
Quote from: "conniecartech"
well, first lets get our jargon on the same page.  Shocked  id go with the icm. unless u wanna take it to a competant shop and get it checked out.


I have an OBDII sensor that hooks up to my laptop, and I actually can get real time data. I don't know what I would want to look at though to find out if it is the pcm though. And is the ICM really small then? Because i looked under the coils and there was was a small, flat metal box thing right under them, but that was it. If that is all it is then it doesn't sound like it will be all that difficult to replace!

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conniecartech

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Re: Good Coil Pack Not Firing
« Reply #5 on: November 16, 2010, 05:09:34 AM »
not sure if your tool will do it, but check to see if the pcm is commanding all the coils to fire. the icm is pretty easy to replace on this one, just pull the coils off and unplug the 14 wire connector, then remove the mounting bolts.


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discretesignals

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Re: Good Coil Pack Not Firing
« Reply #6 on: November 16, 2010, 06:58:10 AM »
If you swapped coils around and you still don't have spark, it needs an ICM.  One of the coil drivers (transistors) in the ICM is bad.   Your getting crank reference, power, and ground to the ICM or else the engine wouldn't start.  You'll still get spark if the bypass goes bad to the PCM, so the PCM won't cause a no spark on one coil.  The PCM only controls ignition timing once the engine's RPM is high enough by grounding the bypass circuit and switching timing control over through the EST circuit.  During cranking, low rpms under 400 rpm, or EST faults the circuitry inside the ICM controls the firing of the coils.
« Last Edit: December 31, 1969, 06:00:00 PM by discretesignals »

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thunderpanda

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Re: Good Coil Pack Not Firing
« Reply #7 on: November 16, 2010, 10:37:03 AM »
Quote from: "discretesignals"
If you swapped coils around and you still don't have spark, it needs an ICM.  One of the coil drivers (transistors) in the ICM is bad.   Your getting crank reference, power, and ground to the ICM or else the engine wouldn't start.  You'll still get spark if the bypass goes bad to the PCM, so the PCM won't cause a no spark on one coil.  The PCM only controls ignition timing once the engine's RPM is high enough by grounding the bypass circuit and switching timing control over through the EST circuit.  During cranking, low rpms under 400 rpm, or EST faults the circuitry inside the ICM controls the firing of the coils.


Hmm that is interesting to me... Because even though it was firing improperly at idle, My car shows by far the biggest problems at medium rpms or higher. I was just asking about this specific problem because, hey, it was an obvious one. When I go to higher rpms it has a lot of trouble and the car has no power... I mean it sounds like i will have to replace the ICM either way, but could my PCM be what is causing my car trouble at higher rpms? I think it has to be either a sensor somewhere or the computer, every other source of ignition has been checked... There might still be some partially clogged injectors but I don't know if that would cause my massive lack of power and god-awful fuel economy

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thunderpanda

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Re: Good Coil Pack Not Firing
« Reply #8 on: November 16, 2010, 10:51:55 AM »
One last thing... I actually have the wires for each coil plugged in reverse order. IE, instead of 145236, it is 412563. Why do I have it that way? Because if I have it the *correct* way, the car runs EXTREMELY poorly. it idles okay... but any gas and it either dies or has an extremely tough time overall. I have asked about this in other forums and nobody has been able to explain it... If somebody understood that whole system enough to explain it, I might be able to pinpoint the source of my problem. I read a complicated explanation of how an ignition control system works, and I found one important piece of information. I thought that the spark that goes out through each post on the same coil was exactly the same. It turns out they are not... The current goes a different direction because the polarity never changes. On one post the current goes out, and on the other the current comes in. But again, if everything was working perfectly, it shouldn't MATTER whether it goes out or in for a given spark plug and thus it should run exactly the same if you switch posts. But it doesn't... Who can figure out why?

Here is the information I read:

"When the coil discharges, both plugs fire at the same time by using the engine block to complete the electrical circuit. The cylinder on the compression stroke is called the event cylinder and the one on the exhaust stroke is the waste cylinder. The two cylinders share the energy available from the ignition coil to fire both spark plugs. This method of ignition is called waste spark ignition.

Since the polarity of the ignition coil primary and secondary windings does not change, one spark plug always fires with a forward current (center electrode to ground electrode) and its companion plug fires with a reverse current (ground electrode to center electrode). This is different from a conventional distributor ignition system that fires all the plugs with the same forward current flow.

It is possible for one spark plug to fire even though a plug wire from the same coil may be disconnected from its companion spark plug. The disconnected plug wire acts as one plate of a capacitor and the engine block acts as the other plate. These two capacitor plates are charged as a spark first jumps across the gap of the connected spark plug. The plates are then discharged as the energy is dissipated as the spark continues. Voltage requirements are very high with an open spark plug or wire. The ignition coil may have enough reserve energy to fire the connected plug at idle, but possibly not under some engine load conditions. A more noticeable misfire may be evident under load; both spark plugs may then not fire.
Read more at http://www.cadillacforums.com/forums/no ... link"

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conniecartech

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Re: Good Coil Pack Not Firing
« Reply #9 on: November 16, 2010, 12:11:17 PM »
yikes, now i got a headache... Confused

what u posted about waste spark systems is true. but lets not turn this into rocket science. the basic problem u got is that one coil aint firing, and changing the plug wires around aint gonna change that.

fyi heres the correct firing order:



i was pretty sure from the start that the icm is bad, and im still sure. but a new one costs over $100, so i wanted to make sure u eliminated other possible causes before plunking down for a new one.

so i think your best bet is to replace the icm, put the plug wires back the way there suppose to be, and clear the codes from the pcm. then take it for a test drive. my gut feeling is that this will fix it, but if something else shows up, we can look into that. let us know what happens.

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thunderpanda

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Re: Good Coil Pack Not Firing
« Reply #10 on: November 16, 2010, 02:43:01 PM »
Ya I am sure you are right... Though i still suspect there is much more than that wrong, mostly because the biggest problem is at higher rpms. But I will replace it and see what happens. Do you know what ICMs I can use? For example, will one for a non-supercharged engine or different year work?

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thunderpanda

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Re: Good Coil Pack Not Firing
« Reply #11 on: November 16, 2010, 03:08:29 PM »
And one other thing, I found a place where I think there is supposed to be a vacuum hose... Not sure where the hose went, and also not sure where the other end of it is. I believe this is the boost control solenoid, or at least thats what someone told me. What do you think? Ignore the finger in the picture, its not pointing at anything. The second picture is for reference so you can see where this is



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conniecartech

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Re: Good Coil Pack Not Firing
« Reply #12 on: November 16, 2010, 04:21:56 PM »
it shouldnt use a diffrent icm if its supercharged. the same part # can be used on diffrent engines and crosses sevral model years. your best bet is to tell the parts place what u got and they can look up the right one.

and id suspect the problem would be worse at higher rpm's. the engine is under load and the plugs gotta fire faster. since u only got 2/3 of them firing anyways, itll affect peformance more then at idle or low rpm's.

that part in the picture is the boost control solenoid. i dont know a lot about the boost system on these cars, but im thinking there should be another vacuum line running to the map sensor which is on the top back side of the engine. not sure if this is related to your problem, somebody else that knows more about these systems can tell u better. it looks like its been missing for some time, and i think u would of noticed a problem before this deal with the coils. and usualy a disconnected map sensor hose will set a trouble code.

but one thing i do know is that this wouldnt cause the icm to not fire one of the coils. u stil need to replace that. start with the known problems and go from there one step at a time.
« Last Edit: December 31, 1969, 06:00:00 PM by conniecartech »

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discretesignals

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Re: Good Coil Pack Not Firing
« Reply #13 on: November 16, 2010, 05:50:43 PM »
The boost control solenoid isn't missing a vacuum hose in that picture.  It's a vent for the boost vacuum actuator.   There is actually supposed to be a little square foam filter that slides over that nipple.  Looks like it rotted away.

Connie's right, you need to fix the misfire before going any further.
« Last Edit: December 31, 1969, 06:00:00 PM by discretesignals »

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losmaster

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Re: Good Coil Pack Not Firing
« Reply #14 on: November 16, 2010, 05:51:52 PM »
I think theres just a foam filter on one end of that.....you can actually see the remains of the original foam in the first photo.....Discrete will know for sure   Laughing
« Last Edit: December 31, 1969, 06:00:00 PM by losmaster »

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