Help me pick a coil (Saab content)

As determined in another thread, it is likely that my 89 900S needs a coil. The issue is that I cannot for the life of me determine the correct stock part except to say that it's Bosch (no surprise) and should be 0.5-0.9 ohms primary and 7200-8200 ohms secondary resistance. This car uses what Saab called the EZK ignition system, which includes an ignition amplifier that is co-located with the coil. Bosch doesn't list a part number for this application, nor do any of the usual suppliers that I've checked. So I'm stuck buying something that I hope will work.

Looking at Summit Racing, there are of course a zillion options. My questions are 1) How critical is it to get similar specs to the original?, and 2) Is there anything beyond those resistance figures that I should be paying attention to when making a choice? For the record, the engine setup is bone stock, and all the consumables - plugs, wires, cap, and rotor - are only a couple years old and good quality stuff.

I may have an '89 non-turbo coil. If you can wait a day for me to rummage for it, it's yours for the cost of shipping. I pulled it from a junkyard car, knowing that they were only used for a couple years.

OR, replace yours with the separate standard Bosch coil and ignition control module that they used on EZK years for all other years. I can likely get you those p/n's, or just look on eEuro and lie about the year -- go with an 87 16V, say.

Try NAPA ECH IC431.

In reply to procainestart :

I don't think I need to replace the ignition amplifier, just the coil; it slides right out of the bracket with the amplifier. Finding the coil for an 87 doesn't seem to be much easier. The few that do pop up (like the ECH IC431 APEowner mentioned) seem quite pricey (~$60 or more). Perhaps I'm just old and can't wrap my head around a simple coil costing that much.

All that said, if you're willing to part with the spare coil, I'll happily accept your offer. Let me know how much and where to send it. Thanks.

Have you got a Bosch number stamped into the body of the coil?  The intertube should give you a buyers guide that will tell you everything it came on.  That gets you to a more sensible car that might have listings.  Also, you can check other part numbers for specs.

If I were doing it, I'd start with comparing to similarly aged Volvo stuff.

There might be a coil that is correct spec, but designed for a different style of coil wire, or with a different diameter or length.  Most of that stuff can be cobbled.

In reply to Streetwiseguy :

The sticker on the coil is long gone. There might be something stamped on it, but if there is, it's tiny and obscured by the ravages of decades of life in an engine bay.

I'll check into Volvo interchange - it makes sense, given that both brands used some pretty similar engine managment setups.

Just another Saab story...I have nothing else to add. 

02Pilot said:

In reply to procainestart :

I don't think I need to replace the ignition amplifier, just the coil; it slides right out of the bracket with the amplifier. Finding the coil for an 87 doesn't seem to be much easier. The few that do pop up (like the ECH IC431 APEowner mentioned) seem quite pricey (~$60 or more). Perhaps I'm just old and can't wrap my head around a simple coil costing that much.

All that said, if you're willing to part with the spare coil, I'll happily accept your offer. Let me know how much and where to send it. Thanks.

I did some digging through a bunch of bins in the ol' Saab parts cellar, but came up short.

I just looked on car-part.com and see used coils for as low as $10, searching with a Htfd, CT, ZIP (I think you're in CT??).

A Saab mechanic on Saabnet says it's very rare that they go bad. I don't know exactly what it is about the one you have, and he may have been talking about the ones mounted to the front cross-member.

In reply to procainestart :

Mine is mounted on the right side inner fender, close to the distributor, behind the headlight.

As far as failure rates, I am not surprised that it's not a high failure item, but mine tests a little out of spec, and the weird missing/power loss I got a few times on initial throttle application from a dead stop seems heat-related (it only happened in high ambient temps). I had a problem similar in my 2002 once that turned out to be the coil, and a few others mentioned it as well in the other thread, so it seems a good place to start.

I'm still curious, if perhaps more intellectually than practically, about the resistance measurements and how critical they are to the coil doing its job properly. I know little about electrical voodoo, so I don't really understand how all the pieces fit together.

02Pilot said:

 

I'm still curious, if perhaps more intellectually than practically, about the resistance measurements and how critical they are to the coil doing its job properly. I know little about electrical voodoo, so I don't really understand how all the pieces fit together.

As far as interchangeability is concerned it really depends on the driver circuit.  If the primary resistance is too low it can damage the driver and if it's too high it's technically possible that it won't work.  The secondary resistance doesn't later from an interchangeability standpoint.  The ratio of primary to secondary is one of the factors the effects power output.

So, as a general rule and lacking more information on the driver circuit try and match the primary resistance if you can't do that go for one with a higher primary.

In reply to APEowner :

OK, that's helpful - thanks. I've read a couple of articles now and I think I have a little better understanding. It appears there are many coils that have 0.7 ohms primary resistance (meaning they fall into the dead center of the 0.5-0.9 range specified in the Saab shop manual), so I would think that one of those would be likely to work, yes?