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Discussion Starter · #1 ·
One of my cylinders is misfiring and I can't figure out what is causing it. I'm currently running some "sea foam" through the fuel system trying to clean out the injectors and valves. I've also changed the spark plugs and neither has helped it out a bit. My car has about half the power it normaly does and it shakes really bad. Also, the check engine light is flashing. when driving it I have to run it up to about 3500-4000 RPM's before shifting or it bogs down really bad. Could it be clogged injectors, sticky valves, bad plug wire, bad ignition system, fuel filter?? I'm really not sure. I would rather fix it myself b/c nobody around where I live will work on a VW, and I really really don't want to take it to the dealership.......because they pretty much just suck (as I'm sure everyone is aware of) Any input would be greatly appreciated!
 

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It sounds very much like an ignition control module. It could also be a coil pack. Assuming you know which cylinder is misfiring, an easy way to test for a bad coil pack is to swap the bad one with a known good one and see if the problem moves.

See this thread for troubleshooting your ICM: http://www.clubb5.com/forums/viewtopic.php?t=66779

For future reference, it's a good idea to let us know your model year and engine.
HTH

Kenny
 

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You need to give us more information like what engine do you have and what year is your car. If you have a V6 you probably have a bad coil pack. If you have a 98-99 1.8T Passat with the AEB engine it is most likely a bad ICM (ignition control module). If you have a newer than 99 1.8T then it is most likely a bad coil pack. It could also be spark plugs.

To test to see if you have a bad coil pack, swap it with another and see if the misfire moves. If you have the AEB engine, test the ICM to see if it is functioning properly; do a search here for testing and locating instructions. These are the basic test so give us more info and we can give you more detailed responses.
 

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Discussion Starter · #4 ·
Thanks fot the feedback. Yeah the ICM could be it! I pulled the plugs off each side of the ICM and My tester was brand new out of the box and I couldn't get a reading off any of the cylinders. i tested the tester on the battery and it did work, so I assume that I'm just retarded and can't figure out how to test the ICM properly. Ok this is a dumb question, but I've only owned my B5 since January, but what is a coil pack? Is it the small box you have to unscrew off the top of the engine to change the plugs?? If so how do you change them?? when I pulled my spark plugs the second one back was solid black, so I assume that is the one that is misfiring but I'm not really sure. Would the solid black plug indicate a bad coil pack though??
 

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You need to plug in a OBD scanner and it will tell you which cylinder is missfiring. Do a search for ICM testing, there is a write-up telling how it is done. Also, try swapping the red with the black when you test the ICM because it is a switch and only always power to flow one way. I tested mine by checking each path ignoring the middle pin on the side with five pins.
 

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jaywku, if you have a 99 1.8t, it's about 95% likely that you have a bad ICM. It's a five minute job. Really easy and accessable. The link in the info forum may have links to suppliers. I haven't checked. The Bosch replacement is pricey, but there are other choices that are much more reasonably priced.

Kenny
 

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Discussion Starter · #8 ·
OK, so when testing my ICM do I need to unplug both sides, or just the 4 pin side. Does the car need to be totally off (meaning key out of the ignition). If I have to unplug both sides, does the red go on the 4 or 5 pin side?
 

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Yes, you need to unplug both sides. Then place the black tester on a pin and the red on the corresponding pin on the other side; for pins 1-4, ignoring the center pin on the five side (this is a ground). Remember that the power will only flow one way so you may need to switch the black with the red. When you find the one that doesn't allow power to flow, this is the bad channel.

There are two replacement ICUs on the market HUCO, which you can get for about $114 at www.busdepot.com and the stock Bosch brand which usually sells for around $200 +; www.ecstuning.com sells both brands. The HUCO brand appears to be reliable (I've had no problems with mine) but it is bigger that the stock Bosch.
 

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Discussion Starter · #10 ·
OK, thanks for all the feedback. I tested my ICM and the second channel was dead! So before I go off and start ordering, I just want to make sure this is correct. Since that second channel is dead then that means I need a new ICM correct?? I've found a wrecked jetta and a wrecked beetle can I pull the ICM's off them to save some dough??
 

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I don't know if the Jetta and Beetle have them or if they are compatible, only the 98 and 99 passats have ICMs. Go to www.busdepot.com and have a new one overnighted; I paid about $150 for the ICM with overnight shipping. Just get the model number from your old unit so you can do a search for the right replacement.
 

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My ICM also suddenly failed today without warning. Driving the couple of miles home I was cussing and swearing (having just experienced a failed ABS module quoted at $1700 to replace - I didn't).

Searching here I came across this post and the great instructions for testing and replacing the module. Between this post and the one about replacing the trunk microswitch I've probably saved over $500.

God, I love the Internet! :) (Though my Passat is testing my patience :mad: )

Kenny Payne said:
It sounds very much like an ignition control module. It could also be a coil pack. Assuming you know which cylinder is misfiring, an easy way to test for a bad coil pack is to swap the bad one with a known good one and see if the problem moves.

See this thread for troubleshooting your ICM: http://www.clubb5.com/forums/viewtopic.php?t=66779
 
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