ignition coils and module replacement
 

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 ?

Depends what is wrong in the ICM. If the a trace to a coil internal on it has degraded, the car will run, but more then likely mis-fire from weak or no spark.

Best thing to do is have the ICM tested on a bench, it's a free test.

I'LL refer to something Jason "The_Maniac" said, and said to me when I had the same problem and the same readings from the auto shop. Coils don't. Normally go bad. If you do have a bad one then replace that one.
I do suggest removing the coils with the wires still attached. 5.5 mm socket. The plug order is 1 and 4, 2 and 5, and 3 and 6. Your original coils are marked. But the new ones may not be. The ICM is easy too.
Be sure to use the new rubber grommets the fit over the electrodes of the ICM. THE old ones may Also have degraded from heat.
My Monte had a bad 2 and 5 coil. I replace all mine cause the Electronic Technician in me would not let me replace only 1, But The _Maniac is right, it's not nessissary to replace them all if only one is bad.
As for the cost to have the shop do it, Pepboys was only going to charge me $429 if I let them do it. I thought that was expensive. It's a Really Really easy job. You can get to job sdone in a half hour under your favorite shade tree. So do it yourself. Good Luck and Safe driving!

When you have it tested have them repeat the test several times in a row so the ICM gets hot. Heat causes expansion and a lot of times an ICM will pass a bench test but fail once back on the car exposed to the under hood heat.

^^^^

Good mention 03SSLE! I forgot about that, but very important (unless it fails on the first crack).

Thanks to everybody that helped I took my coils and module and got them checked and the module was bad all coils were good. Thanks again to everybody...

Glad it was something simple, and hopefully very cheap!

Never be afraid to ask how, and usually things can be done with very basic hand-tools. :thumbsup:

The part was only 152.00 labor free done by me and that's better than 800.00 the shop wanted...

:congrats: You have passed your Initiation into Monte Carlo Enthusiasm. You fixed your car. Now you are 1! :thumbsup:

Awesome!!! Glad this one was solved easily :)

I find a DIY fix that goes easy just makes me feel good :)