[s-cars] ur-S4 high load misfire

[chris chambers]

Cody,

I had the same problem, I diagnosed which coil was bad by using
a spark plug tester like this one:

http://www.toolweb.com/pics/LIS50850.jpg

I bought mine for ~ $6 at Autozone.

Simply unbolt the coil pack and invert it so the spark plug connectors
are pointing up. Attach a cable to one end of the spark tester that
you can connect to ground, insert the other end into a spark plug
connector and have an assistant turn the engine over. Go over all
5 coils and then adjust the tester out farther to create a larger gap
for the spark to jump. Then re-test each coil, eventually you will find
a setting that one coil won't create enough spark to jump the gap, but
the other 4 will. 

You now know which coil is weak.

HTH
Chris


--- cody at 5000tq.com wrote:

> Ok I've just finished up a MRC RS2 software/injector + GT2871 setup
> on  
> my boss/friends '93. Had some issues with the kit, some big some  
> small, but now I'm down to one final issue.
> 
> We have a high boost miss. Car runs perfect in all other situations. 
> 
> Plugs look good, has the F5PDOR plugs in it. All plugs look the same,
>  
> ie I can't pin it to a cylinder based on the plugs. It definately  
> feels like only 1 cylinder is dropping, sometimes it's just an  
> intermittent thing, sometimes it will completely drop a cylinder
> until  
> you lift off. I just changed the coil boots as one showed high  
> resistance, no change at all. Didn't seem to have this issue before, 
> 
> but of course the problem only seems to occur at boost levels higher 
> 
> then stock anyways.
> 
> Any suggestions as to pinning this down? There is another ur-S4 in  
> town that I'd like to borrow the coil set off of, but unfortunately
> it  
> wasn't availible today. Wylie, maybe we can work something out for  
> Monday? If it works better I'd drop by and swap them one evening then
>  
> bring yours back the following evening.
> 
> I thought about buying one coil ($120!!) and trying it on different  
> cylinders, but that would be a PITA with them needing to be hard
> wired  
> in.
> 
> -Cody Forbes
> http://www.5000tq.com
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> 


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