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All 3 Ignition coils died at the same time? (Updated Aug23)

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Old Jul 26, 2006 | 02:33 PM
  #31  
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Running rich should have killed my mileage right? The mileage didn't vary, I was getting exactly the same as before the problems started occurring (~450KM city/ tank, been that way for years).

Wouldn't it'd be weird that I would get spark (and lots of it) when I ground them outside the chamber, but when they are in the chamber there'* no spark?

Air filter is clean, as well, and just replaced it as well at the beginning of the month.

I'll see if I can dig up a cheap multimeter and see if that gives me better results with the coils. I used that Techinfo document exactly. Maybe the nice expensive one I have has inductance cancelling or something.
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Old Jul 26, 2006 | 03:53 PM
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Running rich would certainly affect gas mileage. Don't forget that something changed to make it stall. It could have been rich for an hour then stalled.

A spark jumps the gap because that is the path of least resistance. It'* easier for the current to jump the gap than travel through ceramic. Cover the ceramic with gasoline & now it'* easier for the current to run through the gasoline instead of jumping the gap. Hence it sparks outside where it'* dry but not inside. If you don't think the plugs are dirty or wet enough to short out then don't change them. You've seen them, I haven't.
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Old Jul 26, 2006 | 04:05 PM
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I worked on an '87 Bonneville that had jumped a couple of teeth when the camshaft gear went. Wouldn't start, and didn't backfire. Listening to the intake while cranking, it sounded like air was being pushed out, rather than pulled in. Pulling a plug and putting my finger in the hole, there was little compression, and at times it wanted to pull my finger in, rather than push it out. Just some quick tests to try to maybe help rule out that possibility.

The difference is that those engines had some trouble with the timing gears and chains. It has become much less of a problem with the "newer" ones.
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Old Jul 26, 2006 | 07:26 PM
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Gentlemen, would PCM be a possibility at this point, or was it said that the PCM doesn't have anything to do with the engine catching initially?
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Old Jul 26, 2006 | 09:23 PM
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The ICM handles the spark initially, before it passes it over to the computer. However, I believe the injectors are entirely controlled by the computer.

That being said, with cars being what they are, I had a situation with an '89 where everything pointed to the ICM being bad with a stalling and no start problem. Wrong...it was the computer.
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Old Jul 26, 2006 | 09:37 PM
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If the PCM is responsible for the injectors, could the injector drivers be stuck "on", causing constant spraying of fuel into the combustion chambers? That might explain the indications of running rich and the wet spark plugs.
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Old Jul 26, 2006 | 09:56 PM
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Yes, it could, but I'd expect the fuel pressure reading to be quite low. I think the banks are split too, so I'd expect only half of them would be wet unless both drivers failed, which wouldn't seem likely.
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Old Jul 26, 2006 | 10:32 PM
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Well, unplugging the MAF didn't do anything.

I hope it'* not the PCM, I don't have the 500+ bucks it'll cost me to replace it...
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Old Jul 26, 2006 | 11:11 PM
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Well, I've pulled all the plugs and cleaned them up. I'll leave em out of the car for a day to let any excess gas in the chambers evap out.

Any other tests/things to try before I call it a loss and haul it to the dealer?

Crap, this has been such a good car up till now.... :(

Edit: I found my plugs from the last swap, they should be okay, just regular copper plugs instead of platinums. I'll swap these back in when I test it again, just in case I've fried the NGK platinums.
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Old Jul 27, 2006 | 02:19 AM
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Originally Posted by Arbelac
I hope it'* not the PCM, I don't have the 500+ bucks it'll cost me to replace it...
A replacement PCM will not cost you $500. It might cost you $50-$100. Call around to a few junkyards for a '96 Bonneville PCM. I'm not sure if the '96 has a knock sensor module that needs to be swapped over like the '97s. Even if the new PCM didn't work right from the yard, you could have a dealer reflash it without too much hassle.
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