Well the other day I changed my Plugs and my oil. When I took the old plugs out 5 and 6 had oil in the gallies (valve cover seals leak). I soaked as much of it up as I could before I took the plug out. I then put in Autolite 3923's gapped to .029. Of course there was smoke on startup due to the oil in the gallies. But now when my car sets at idle; at operating temperature it sputters a little. Sounds like a backfire almost but it's real muffled. The tach hovers at around 600-700 rpm and when it sputters it drops to just above 500 for just a split second and hops back up to normal. I was thinking one of my plugs could be ruined from the oil ordeal and I need to install a new one or replace all six again. Only mods are K&N, AEM TRU Boost, and Bosch Bypass valve. Car runs fine except when idling. Any info and help is appreciated thanks Bill.
Sputtering at Idle after change of sparkplugs
- Thread starter billwert
- Start date
Autolite 3923 plugs are about 1/8" shorter than the stock spec...this can cause arcing due to the plug not fully seating on the plug wire. Had the the exact same thing happen w/ MSD wires. Swap over to NGK's and it will be gone 
NGK Copper spark plug 2330 (BCPR6ES) .032" gap
NGK Copper spark plug 3330 (BCPR7ES) .032" gap - 1 step colder
NGK Iridium spark plug 5689 (BCPR6EIX) .032"
NGK Iridium spark plug 5690 (BCPR7EIX) .032" - 1 step colder
The above copper plugs are equivalent to the Autolites.
Iridiums will last longer, but are more expensive and can "glow plug" after hard, long runs.
Higher boost = colder plug, less gap - .029" is a good start point.
Good info:
http://www.supramania.com/forums/showpost.php?p=471693&postcount=19
NGK Copper spark plug 3330 (BCPR7ES) .032" gap - 1 step colder
NGK Iridium spark plug 5689 (BCPR6EIX) .032"
NGK Iridium spark plug 5690 (BCPR7EIX) .032" - 1 step colder
The above copper plugs are equivalent to the Autolites.
Iridiums will last longer, but are more expensive and can "glow plug" after hard, long runs.
Higher boost = colder plug, less gap - .029" is a good start point.
Good info:
http://www.supramania.com/forums/showpost.php?p=471693&postcount=19
Wait... iridium will "glow plug"... ?
What are you better off running then, copper or iridium? I know copper doesnt last as long as iridium, but, how bad do the iridium glow plug then???
What are you better off running then, copper or iridium? I know copper doesnt last as long as iridium, but, how bad do the iridium glow plug then???
Rennat;939714 said:
Been running Denso Iridiums in several 800+ whp cars for a while now. No problems "glow plugging" here. Get the correct heat range for your application.
Also, scrap that center valley cover and you don't have to worry about JIS plug height anymore.
Depends on what you do with the car and they "can" glow plug
Like I said, long, hard (high speed) runs or a series of short WOT (drag racing) runs with little time in between. For the majority, it's not a problem. The other issue is iridium is not as effective conductor (both heat and electricity) as copper. IMO, copper is a better plug...it just requires you to change plugs more often. Either will work well though and the iridiums seem to have a better idle.
Like I said, long, hard (high speed) runs or a series of short WOT (drag racing) runs with little time in between. For the majority, it's not a problem. The other issue is iridium is not as effective conductor (both heat and electricity) as copper. IMO, copper is a better plug...it just requires you to change plugs more often. Either will work well though and the iridiums seem to have a better idle.
jdub;939801 said:Depends on what you do with the car and they "can" glow plug
Like I said, long, hard (high speed) runs...
Like back to back to back highway roll ons up past 160 at 30+ pounds of boost?
Copper does allow for a weaker ignition system to fire a denser charge than Iridium. It got annoying changing them every weekend though.
Just had a high speed miss that the only way I could stop it was switching to the same heat range coppers.
chevyeater;939817 said:
That's why I'm running iridiums now actually...when I get the FFIM set-up installed, it's back to the coppers. With all the extra parts to remove gone, it'll be a snap to change plugs.
I have to run about a .003" smaller gap to get the same performance out of iridium plugs compared to copper. But then again, I've had a few sets running around in some crazy cars for more than a year without having to change them or losing any performance. Some of those cars were eating 2 sets of copper plugs in one night!
I got down to 20 thou on the IR's and it was still doing it changed out to coppers and it went away so the only thing I could think of was it was overheating the tips.
LPG doesn't seem to destroy Coppers like gas/petrol so I get good service from them.
LPG doesn't seem to destroy Coppers like gas/petrol so I get good service from them.
LPG is pretty hard to light though Ian. Those stupid Cavaliers I used to work on were slow as balls before they picked up a miss...