Does anybody know how difficult to replace the coils and module and can it be done at home ?

 

It's very very easy.

You just label all of the plug wires before you remove them, then it's just 2 bolts per coil (I want to say they are small 5.5mm bolts). Then you remove the ICM from under them. I don't recall the ICM removal procedure off the top of my head.

 

It is not a difficult job and can be done at home. Disconnect the + battery terminal, then remove the plug wires (make a diagram to reference when replacing) and unplug the electrical connector. Remove the 4 screws that hold the module on and you can remove it and the coils as an assembly.

 

I believe on a 3800, the wiring harness for the ICM is bolted in (probably a 7mm). Like everyone said, easy task.

Just out of curiosity, why are you removing them?

 

It running like it's missing firing and I took it to a shop and told 1 coil was bad and also the module need to be replaced...The want 875 dollars to replace

 

First, for $875, those coils better be AMAZING!!! The coils and ICM are not that expensive and the labor is quick/easy.

I would double check their findings. Coils RARELY fail. They fail, but again, rare.

As for the ICM, remove it from the car, take it to almost any autoparts store. Many stores can bench test it. Do that BEFORE chucking money at it. If it fails, replace that FIRST. You may have an issue with the ICM and no issues with a coil.

If any of the tips on the coils are corroded, get a scotchbrite pad and clean them. Make sure to re-grease the plug boots with die-electric grease (helps keep moisture out, fight against corrosion and make it easier to take the wires off next time).

If it's still mis-firing if you have the factory plugs OR you've put about 100,000 miles on platinums or irridium plugs OR if the plugs you have are BOSCH plugs, change them. Plats and irrids are good for about 100,000-150,000 miles. BOSCH plugs are garbage in a GM v6. Stick with AC Delco or NGK (my 3400's all have NGK plats, my 3800 Monte is still original).

If you still suspect a coil, just my experience, don't use the auto parts store non-OEM. Either grab a replacement from a junk yard or a new OEM. The few times I've had a factory coil fail, the after market replacement failed before any others.

Hope this helps!!

 

My monte carlo has over 160,000 miles on it that many miles do you think they might go out?

 

I also had the plugs changed about 3 yrs ago with ac delco ones

 

GM has used those same coils for years (the same coils are in the 3100 from 1994, until the 3400 I think ending in '05 and the L36 3800, the supercharged 3800 actually has different coils). I know cars with over 200,000 miles on the factory original coils. In my opinion, mileage doesn't mean that much with these coils. They "might" degrade some over time, but not usually anything significant. I would NOT look at those as my first source of a mis-fire.

Now, your plugs, did you put platinum, irridium or copper plugs? How many miles are on the plugs? That is a deciding factor. Copped I find last about 50,000 miles. Plats and Irrids last 100,000-150,000 miles. If you drive a lot, and you are close to 100,000, I would suspect plugs before coils.

Like I mentioned, start with taking the ICM, get that tested. If it fails, replace it. See if the problem goes away. If you are still having trouble, you can prove if it's the coil if you know which cylinder is misfiring, just switch the coil with another one and see if you problem follows the coil. If it does, then it is the coil. If it doesn't you have another problem (plug, plug wire, fuel injector to name a couple possible causes for a mis-firing on a specific cylinder).

Between friends/family, I've worked on a lot of high miles cars that use these coils (over 10 at least). Out of all those cars, I think only 2 MAYBE 3 ever had a single coil fail (and of those, they had the aftermarket replacement coil die about 2 years later).

 

If it was the icm that was the problem would the car still run ?