Coil went bad, car was smoking, why?

[GnatGoSplat]

A coil went bad on my 89 on Sunday. At first, I wasn't sure it was a coil, because when I opened the hood, smoke was coming out from that tiny gap between engine and firewall. Really stinky smoke at that, like really rich exhaust. The engine was vibrating and running like ass. I let it sit for about 10-minutes, started it back up and got my drop light to look for the source of the smoke. It didn't smoke right away, but after running about 10-minutes, it started smoking again. I never could tell where it was coming from, it just seemed to emanate from behind the engine like a ghostly apparition. I got my trusty inductive timing light, and verified cylinders #2 and #5 not firing, both on the same coil.

 

The next day, I got a new coil from O'Reillys... $12.12 incl tax, thanks to my friend's employee discount.

 

Now the car is fine. Drives great. No smoking. WTF?

 

My theories:

1. Smoke was coming from an exhaust leak that's always there, just that with a good coil, it burns cleanly so no smoke is visible. I'm slowly being poisoned by CO and if I should take a long trip, I might find myself getting very, very sleepy.

2. Smoke was coming from a leak caused by the engine vibration (perhaps from rear manifold to downpipe connection - exhaust was clattering with bad coil). With no vibration, everything is fine (no need to worry).

3. Smoke was caused by unburned fuel leaking past cylinder walls and into crankcase, where it was vaporized by heat and was coming out through the PCV (which I don't think is all that tight-fitting). That would explain why the engine has to be hot for the smoke to appear.

 

Thoughts?

 

Oh yeah, that coil was an original with 203k miles on it and 17yrs old. Not bad, not bad at all. Believe it or not, the car still has one original coil left!

 

While pricing coils on eBay, I also noticed a lot of newer GM engines (i.e. 3.5L 60-degree V6) uses a coil assembly with all 3 coils integrated. How is that a good idea? Seems very wasteful, IMO.

 

[White93z34]

i'd personally wager that you could be very well right on all 3 counts, however i'd say cases 2 and 3 are most likely. i forget what kind of exhaust manifold gaskets these cars use, but unburned fuel may have been escapeing from there.

[SigEpCutlass]

I think all 3 of your theories could very well be valid. Not sure what to tell you Shawn.

[GOT2B GM]

All 3 scenarios are feasble, but I'm betting on the fuel vapours leaking out of the PCV.

 

Do you have an audible exhaust leak?

 

An integrated coil assembly is just a way to make more money, instead of replacing a $20 part, you replace a $60+ part.

[GnatGoSplat]

Yeah, I'm not too worried about it, just kind of curious. If I should get very sleepy, I'll just open a window.

 

Nah, I didn't notice an audible exhaust leak, but I can't really hear much over the fans and belt-driven accessories. If there's a leak, it's certainly quieter than the normal sound of the running engine.

 

 

[1990lumina]

If you had an exhaust leak you would hear it IMO....most of the time (I agree depending how bad they are) they are quite loud... I think scenerio #3 seems like a good way to explain it!

[slick]

Out of all of them, #3 seems right to me. With #2 and #5 not sparking, the unburnt fuel is being pushed out to the exhaust, where it is being cooked there. You were most likely picking up smoke through either your EGR(where the tube connects to the exhaust), or through your PCV.

[5speedz34]

 

 

An integrated coil assembly is just a way to make more money, instead of replacing a $20 part, you replace a $60+ part.

 

General Motor's isn't in the market of making money off of parts, they are in the market of selling cars. A large majority of these parts are made by 3rd party manufactures that GM outsources. Although, chances are with ignition parts its made by Delphi. IF anything the reason the coils are integrated are because its cheaper to manufacture than one single coil.

 

Not all companies are the big bad money hungry corporations people make them out to be.

[DiscoStudd]

Another theory is that the gasket (or "donut" if you weeeee-el) betwen the exhaust manifold and the downpipe shrinks when the exhaust cools. You then would get a bit of an exhaust leak before the engine fully warms up, allowing the "donut" to expand to its proper size.

 

That's what I've been led to believe all these years when it's happened on some of my old junkers (mainly because it only tended to happen in the winter.)

 

But seeing as you had some engine vibration, it might be a good idea to disconnect the DP from the rear mani and check the donut for any visible damage, and check it for proper orientation. That and it probably wouldn't hurt to coat the DP-to-manifold flange bolt threads with anti-sieze while you got 'em out...

[5speedz34]

Another theory is that the gasket (or "donut" if you weeeee-el) betwen the exhaust manifold and the downpipe shrinks when the exhaust cools. You then would get a bit of an exhaust leak before the engine fully warms up, allowing the "donut" to expand to its proper size.

 

That's what I've been led to believe all these years when it's happened on some of my old junkers (mainly because it only tended to happen in the winter.)

 

But seeing as you had some engine vibration, it might be a good idea to disconnect the DP from the rear mani and check the donut for any visible damage, and check it for proper orientation. That and it probably wouldn't hurt to coat the DP-to-manifold flange bolt threads with anti-sieze while you got 'em out...

 

If that gaskets never been replaced I would do it under maintenance. It shouldn't cost more than $10 to do the whole job.

[GOT2B GM]

 

An integrated coil assembly is just a way to make more money, instead of replacing a $20 part, you replace a $60+ part.

 

 

General Motor's isn't in the market of making money off of parts, they are in the market of selling cars. A large majority of these parts are made by 3rd party manufactures that GM outsources. Although, chances are with ignition parts its made by Delphi. IF anything the reason the coils are integrated are because its cheaper to manufacture than one single coil.

 

Not all companies are the big bad money hungry corporations people make them out to be.

 

true....never looked at it that way. It just sucks when the average do it yourself mechanic has to pay triple for a part that only is 1/3 worn out.

 

[19Cutlass94]

You wouldnt see smoke from unburned fuel. Your just gonna kill your rings. Seems like an exhaust leak if you were smelling that and it was rich. Ive never seen a coil smoke before and I dont even know if its possible.

[GnatGoSplat]

Good point, although strange thing is the exhaust from the tailpipe wasn't visible, just the smoke underhood.

It could be the donut gasket. I should probably replace it anyway since it's original, but I'll probably procrastinate on that.

 

Nah, I'm pretty sure the coil itself wasn't smoking. The smoke was coming from the wrong end of the engine to be the coil itself.

 

BTW, the bad coil tested good on the ohmmeter. I learned not to trust that a long time ago, but just thought I'd mention it.

 

 

[5speedz34]

 

 

An integrated coil assembly is just a way to make more money, instead of replacing a $20 part, you replace a $60+ part.

 

true....never looked at it that way. It just sucks when the average do it yourself mechanic has to pay triple for a part that only is 1/3 worn out.

General Motor's isn't in the market of making money off of parts, they are in the market of selling cars. A large majority of these parts are made by 3rd party manufactures that GM outsources. Although, chances are with ignition parts its made by Delphi. IF anything the reason the coils are integrated are because its cheaper to manufacture than one single coil.

 

Not all companies are the big bad money hungry corporations people make them out to be.

 

You didn't say anything.

[Bake82]

 

 

An integrated coil assembly is just a way to make more money, instead of replacing a $20 part, you replace a $60+ part.

 

true....never looked at it that way. It just sucks when the average do it yourself mechanic has to pay triple for a part that only is 1/3 worn out.

General Motor's isn't in the market of making money off of parts, they are in the market of selling cars. A large majority of these parts are made by 3rd party manufactures that GM outsources. Although, chances are with ignition parts its made by Delphi. IF anything the reason the coils are integrated are because its cheaper to manufacture than one single coil.

 

Not all companies are the big bad money hungry corporations people make them out to be.

 

You didn't say anything.

 

 

Sure he did....he just didnt type it in the right place!

[5speedz34]

 

 

An integrated coil assembly is just a way to make more money, instead of replacing a $20 part, you replace a $60+ part.

 

true....never looked at it that way. It just sucks when the average do it yourself mechanic has to pay triple for a part that only is 1/3 worn out.

General Motor's isn't in the market of making money off of parts, they are in the market of selling cars. A large majority of these parts are made by 3rd party manufactures that GM outsources. Although, chances are with ignition parts its made by Delphi. IF anything the reason the coils are integrated are because its cheaper to manufacture than one single coil.

 

Not all companies are the big bad money hungry corporations people make them out to be.

 

You didn't say anything.

 

 

Sure he did....he just didnt type it in the right place!

 

Ohh shit, yeah I see that!

 

 

[Crazy K]

While pricing coils on eBay, I also noticed a lot of newer GM engines (i.e. 3.5L 60-degree V6) uses a coil assembly with all 3 coils integrated. How is that a good idea? Seems very wasteful, IMO.

well... if you look at the shortstar 3.5 is has a coil/icm that costs $200 to replace. It mount on top of the valve cover and has the direct fire 'tubes' with three plug links per side. My friend traded in an aurora with 99k miles that had constant misfires. I think it had a intermittant coil/icm IMO it makes the parts more expesive, but may better sheild them from nature and possible failure.

 

Another theory is that the gasket (or "donut" if you weeeee-el) betwen the exhaust manifold and the downpipe shrinks when the exhaust cools. You then would get a bit of an exhaust leak before the engine fully warms up, allowing the "donut" to expand to its proper size.

 

That's what I've been led to believe all these years when it's happened on some of my old junkers (mainly because it only tended to happen in the winter.)

 

But seeing as you had some engine vibration, it might be a good idea to disconnect the DP from the rear mani and check the donut for any visible damage, and check it for proper orientation. That and it probably wouldn't hurt to coat the DP-to-manifold flange bolt threads with anti-sieze while you got 'em out...

 

If that gaskets never been replaced I would do it under maintenance. It shouldn't cost more than $10 to do the whole job.

cost 6.99 from AZ iirc. heat expansion should not play an issue, since the down pipe is connected with spring loaded bolts. It is compressing the donut. BUT the donut does need to be replaced every 100k miles, becasue it is made of steel with a composite graphite coating. the graphite acts and the seal but weats away of years of vibration. I replace this on all my cars as regular maintnence, ESPECIALLY since it often rattles when worn out.

As for winter... you see the exhaust vapor better the int winter, so it mostly likely that you just noticed it.

yes anitsieze is your friend!

 

Good point, although strange thing is the exhaust from the tailpipe wasn't visible, just the smoke underhood.

Hey! Don't forget... the catalytic converter. It's not respected but it does actually process what would otherwise be visible smoke in the exhaust, beyond just processing noxious gs ans exhaust fumes. Asusming it is present and not over leaded with a really smokey engine.

 

I have wondered about the life of coils myself. My lumina at 222k has the OEM type ones with the proper cylinder markings... might mean they are original, or proper OEM replacement. but the ICM quit while I was in viginia in april or may... at 215k.

[GOT2B GM]

 

 

An integrated coil assembly is just a way to make more money, instead of replacing a $20 part, you replace a $60+ part.

 

true....never looked at it that way. It just sucks when the average do it yourself mechanic has to pay triple for a part that only is 1/3 worn out.

General Motor's isn't in the market of making money off of parts, they are in the market of selling cars. A large majority of these parts are made by 3rd party manufactures that GM outsources. Although, chances are with ignition parts its made by Delphi. IF anything the reason the coils are integrated are because its cheaper to manufacture than one single coil.

 

Not all companies are the big bad money hungry corporations people make them out to be.

 

You didn't say anything.

 

 

Sure he did....he just didnt type it in the right place!

 

Ohh shit, yeah I see that!

 

 

 

fixed

[Supreme Cutlass]

 

 

An integrated coil assembly is just a way to make more money, instead of replacing a $20 part, you replace a $60+ part.

 

General Motor's isn't in the market of making money off of parts, they are in the market of selling cars. A large majority of these parts are made by 3rd party manufactures that GM outsources. Although, chances are with ignition parts its made by Delphi. IF anything the reason the coils are integrated are because its cheaper to manufacture than one single coil.

 

Not all companies are the big bad money hungry corporations people make them out to be.

The dealership sure seems to be...

[19Cutlass94]

Actually, you say the dealership is bad, but really the the dealerships around here ( GM ) dont charge any more than NAPA or autozone really.

[mfewtrail]

What brand coilpack did you get for $12 Shawn?

[GnatGoSplat]

It's a "Master Pro" with a prominent "MADE IN CHINA" stamped on the top of it.

1-year warranty so I'm not worried. It was less than half the price of the Borg Warner.

 

[mfewtrail]

It's a "Master Pro" with a prominent "MADE IN CHINA" stamped on the top of it.

1-year warranty so I'm not worried. It was less than half the price of the Borg Warner.

 

 

Ah, I was just checking. I was hoping you were gonna say "AC Delco" so I could send you some cash to buy me about 6 of them @ that price.

[Supreme Cutlass]

Actually, you say the dealership is bad, but really the the dealerships around here ( GM ) dont charge any more than NAPA or autozone really.

Here they charge about double what's on GM parts direct. The lateral link that was 55 from GMPD would've cost upwards of $100 from the dealer. Once they charged me around $25 for a plastic knob.

[19Cutlass94]

I know when I needed a new IAC, I looked at NAPA's price v the dealer price, and it was cheaper at the dealer. I guess it depends on what part and where you live?