3.4 ignition coil fault but it checks out ok?

[malc_p]

(reposting, first try has disappeared into the ether...)
Weird.
My 3.4 Firebird developed a misfire on # 3 (diagnosed by disconnecting leads one-by-one until the engine note didn't change; confirmed by the plug being wet when I removed it). On inspection I found a chafed plug lead where it ran under the plenum so I replaced that (as well as all plugs) and the misfire stayed there. I then swapped the 3-6 coil with the 2-5 coil and the misfire moved with the coil; aha!
But...I then took the oil off and did the ohmage checks - everything's fine. 0.9 ohms primary, 5.7k ohms secondary, no shorts between primary and secondary and no shorts to earth. But when the coil is on the car, there is absolutely no spark at the #3 post. I can put a screwdriver on it and lean it against the plenum, no spark, nada.
I guess the chafed lead overloaded the coil somehow and there's internal damage? Looks like a new coil pack is in order anyway.
Bummer.

[tkoforpresident]

Re: 3.4 ignition coil fault but it checks out ok?

yeah they're like 35$ each. I'd sack up and buy one rather than worry about the mystery of it all which sounds rather perplexing.

[Slowside]

Re: 3.4 ignition coil fault but it checks out ok?

Man you cant just buy one. When you do this you have to replace all three.


From what I understand, that if you put a new one in the line of three, that the older ones will wear much quicker. SO when you do this, you want them to be the same strength, so they wear evenly.

[nascar24jd]

Re: 3.4 ignition coil fault but it checks out ok?

I had one go bad and replaced all 3 the next day. It is cheap insurance and not worth messing around with.

Just replace all three of them.

[tkoforpresident]

Re: 3.4 ignition coil fault but it checks out ok?

you dont HAVE to replace all three at once. that is ridiculous. I'm not saying i didnt, because i did. It's more convenient. But many people just replace one at a time.

[malc_p]

Re: 3.4 ignition coil fault but it checks out ok?

"Just buy 3".
Yeah, right. Gotta remember here I'm in the UK.
The coils may be just 35 bucks over there, and I've seen them on ebay for $20 (mailing to the uK is $35 so $95 all up), but OVER HERE I just had to pay 70 pounds sterling for ONE. That's $112. I would have ordered the ebay ones but I can't afford to have the car out of action for the three weeks it would take to get them delivered.
We pay outrageous prices here for parts.
:rant:

[nascar24jd]

Re: 3.4 ignition coil fault but it checks out ok?

"Just buy 3".
Yeah, right. Gotta remember here I'm in the UK.
The coils may be just 35 bucks over there, and I've seen them on ebay for $20 (mailing to the uK is $35 so $95 all up), but OVER HERE I just had to pay 70 pounds sterling for ONE. That's $112. I would have ordered the ebay ones but I can't afford to have the car out of action for the three weeks it would take to get them delivered.
We pay outrageous prices here for parts.
:rant:

If you update your profile to show that you live in the UK then we would know that. Glad to hear you solved your problem.

[malc_p]

Re: 3.4 ignition coil fault but it checks out ok?

Sorry, my bad - I've updated my profile to show my location here in the (occasionally but currently bitterly cold) south coast UK.
Anyway, back to the car.
It ran fine for the last few days but yesterday it just refused to start.
I have good sparks on all 6, fuel pressure is ok, leads are good but it just spins over and over giving a cough every now and then.
If the car had a distributor and points, I'd say the timing had slipped or the condensor had failed, if you see what I mean.
I'm guessing maybe the failed coil pack last week fritzed the ignition control module? Or maybe the crank position sensor has died?
Anyone have any clues where to look next?
Many thanks
Malc