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Discussion Starter #1
Just trying to track down my misfires on the 24v and it seems like I found the culprit. The middle coil on the front don't seem to change the idlewhen unplugged. If any of the other 2 are unplugged the idle changes. The weird thing is that sometimes the car jumps from misfiring to normal on it's own. I checked the resistance and I was getting 0.08 ohms on all front coils. I was also getting 12v from the plug (harness). Is this within spec and what are the specs? Could it be an arching coil or maybe damaged wiring at the plug do this? I tracked down a bad wiring in the injector harness that caused intermittent working conditions.
 

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Since the resistance of the coils are all similar, try swap them to see whether problem moves with the coil or stay at cyl #5. Also try swapping the ignition modules connectors to see whether the problem moves or stays!
 

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coils and ohms

Generally its not really useful to measure resistance of coils at low voltages, unless they are shorted, or open (ie frank breakage). Normally what happens is the insulation breaks down under higher voltage, and thats what causes a 'temporary' short to ground, say.

I would pull the plug on the coil in question and look at the gap, then once I was sure that plug was OK, change the location of the coil to an adjacent one.

I had one a while ago that was arcing and cracking and when I pulled the plug, the gap was WAY WAY too large! Readjusted the gap and all was cool---
 

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Discussion Starter #4
Found the problem one of the ignition control units is misbehaving when hot. I checked the prices they are ridiculesly priced at $290. I found some at german autoparts for $95 a piece made by a german company called HUECO. Anyone heard of this brand and any experiences?
 

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Discussion Starter #5 (Edited)
Okay update found another website called carstuff.com they have the bosch units for $178 and HUECO for $93. It seems that a 1994 Volvo 960 uses the same ignition module
 

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Hi,
I have a problem with the rear bank on my 24v which I am now certain is ignition based (rough idle especially when warm). Have tried swapping over the ignition modules and it stays on the rear so does that mean it is either the rear ignition module or the rear ignition packs found on each of the rear plugs or am I confusing myself?

Thanks,

Richard
 

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Discussion Starter #7
Yours are more likely coil packs. Or could be both you have to test it yourself. When I change plugs on my modules it moves from front to rear. And the coil that wasen't working before works.
 

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Yours are more likely coil packs. Or could be both you have to test it yourself. When I change plugs on my modules it moves from front to rear. And the coil that wasen't working before works.
Thanks BlackFXGT but can I ask what tests you would suggest? My problem stays on the rear bank when I swap the ignition feeds by the air intake. When you say plugs are you referring to spark plugs or something different?

Thanks.
 

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pluds that are connected to the ICM(ignition control module) Try swapping coils from front to back if it still stays in the back than your ICM is bad as mine is. Well I found the cheapest I can find for $69
volvo part# 1367776
Hueco part# 138403
Bosch part# 0 227 100 203
FCP Groton-Volvo S90 and V90 Engine Elctrical Parts
Sorry, don't mean to be thick, but where exactly are the ignition control modules? Thanks.
 

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Discussion Starter #12
ICM is located by the airbox under the black cylinder. You can't miss it there is 2 of them with 7 plug pin each. As for testing coils I tried with the ohm meter to get a resistance. But as you read earlier it's not really accurate.
 

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Found the problem one of the ignition control units is misbehaving when hot. I checked the prices they are ridiculesly priced at $290. I found some at german autoparts for $95 a piece made by a german company called HUECO. Anyone heard of this brand and any experiences?
Yes, I had a bad Bosch ignition module on my '94 LS and I put in a HUECO/HUCO ignition module (another "al cheapo" solution :)). It has been working fine for at least 2-3 years. I also added a heat sink (have one lying around at that time) on top of the modules to help cool them though I think the bottom heat sinks (where the modules are mounted) are more important. Use good thermal grease to re-install them! Also if somebody installed a black plastic cover next to the left side of the radiator (in front of the modules), remove it during the warm seasons to provide better cooling to the modules.
 

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Yes, I had a bad Bosch ignition module on my '94 LS and I put in a HUECO/HUCO ignition module (another "al cheapo" solution :)). It has been working fine for at least 2-3 years. I also added a heat sink (have one lying around at that time) on top of the modules to help cool them though I think the bottom heat sinks (where the modules are mounted) are more important. Use good thermal grease to re-install them! Also if somebody installed a black plastic cover next to the left side of the radiator (in front of the modules), remove it during the warm seasons to provide better cooling to the modules.
Thanks a lot for that. Appreciate it.

Richard :)
 
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