helping a friend on his 95 trans am.

motor was pulled and refreshed, fitted with trick flow 195 assembled heads, comp cam, electric water pump and reinstalled.

using new delco wires, NEW opti, new cap/rotor, new msd coil, old msd 6 box

WAS using ngk 7173 non resistor plugs at first:

car has had a part throttle misfire and generally running poorly and not responding to tune changes, in general it runs ok on fresh plugs but as the misfires happen it shows lean on the 02's and the computer starts adding fuel in closed loop and slowly fouls the plugs until the car runs REALLY bad.

happened to look at the engine running in darkness and noticed blue flashing comming from all of the spark plug boots to the hex of the spark plugs..

its NOT an arc strike, but more of the ceramic of the plug itslef GLOWING blue for a split second. ive never seen this before in my life

we changed the plugs to a resistor 6962 ngk as advised by ngk but SAME THING! glowing spark plug ceramic (looks like flashing light blue on all 8 plugs between the boot and the block)

we are doing more hunting of bad grounds/bad + but finding nothing so far

any ideas appreciated.

 

You are either suffering from Corona effect or flash over. Corona effect is sometimes caused by the right (or wrong) environmental conditions causing a glow around the ceramic insulator. Google some sources on it. Here is one from NGK http://www.ngkspark.com.au/sparkplug_tech.php# click on spark plug analysis. Try cleaning the ceramic real well, be sure the contacts are tight and use dielectric grease on the contacts.

Flash over is sometimes caused by too large of electrode gap. If the problem is NOT corona effect, I would try closing the gap another 5 or so thousandths.

 

so corona discharge is just a thing that we see, and not an actual misfire according to that ngk site.

the plugs were brand new, this was observed on first start up with new plugs (6962) everything was clean and with dielectric grease.

ill have to verify the gap

for comparison and evironmental, my car (ls1) was not showing any glowing with the 7173s when viewed idling in darkness at the same time same place as the lt1 with 7173's was viewed with this flashing. i use msd wires however compared to the ac delco wires.

 

variations in things from vehicle to vehicle will effect it. Not to mention the power of the coil, distances etc......

Try running the vehicle in question with an O2 disconnected to force it into open loop all the time. See if it then runs well. If so, the problem is control and not actually the ignition system.

 

If you are using stock Delco 7mm wires and a MSD 6a box,that could be your problem..I would switch to a MSD 8.5 wire.

 

cool thanks

 

FYI my car has done this for 5 years now. Its frustrating as all hell! Im far from stock, but I set everything up per other peoples suggestions with what works. I gave up on it, as mine runs amazing. No missfires or anything. It is still annoying to open the hood at night and see that though. I spend 3 months trying to get rid of it with no luck.
Im subscribing to see if you find a cure.

 

Previous posts have suggested removing the box(MSD),and see what happens.Hope this helps.

 

we are going to bypass the msd to quicky eliminate that, and have a fresh set of msd's on deck provided no change.

we also have some grouds we are going to strap a dedicated ground from each head right to battery negative to see what it changes if at all

we use dielectric grease consistantly.. i can only assume the more we use the more it will HELP.. not hurt.. agreed?

 

combination of removing the msd box from the loop and or fooling with wire routing seems to have helped considerably

 

IMO the MSD box is too much for stock 7mm wires,if you replaced them with the MSD 8.5 wires you should be fine to use the MSD box again.

 

Interesting, I dont use an MSD box, but on my second set of MSD 8.5mm superconductors and they do this. Also, I tried Taylors first and they did the same thing...

I wish someone would figure out what does this so I can make it go away on my car!

 

we are going to do a msd, non msd direct comparison this evening!

 

Might look into the wires going to the opti.The moderators have had dealings with this I think.

 

Here is a long shot but are you running an after market alarm system?Might disconnect it for this test.beer time.