ZR-1 Net Registry Forums - View Single Post - spark plugs for a full top end ported engine

A26B · 08-10-2009

Johnny,

A "weak" spark will show up more as a "miss" when the engine is under load such as 65 in 6th gear, than it will at higher revs or at an idle. It's not a dead cylinder problem until it's under a load like you described.

When you check spark, put an old plug in a plug wire, lay it on the plenum & start the engine. It should jump a nice, blue spark 3/4"~1" as you pull the plug away from the engine. If you see an orange spark, it's weak.

I have personally seen at least 3, single cylinder, weak spark issues fixed by replacing the coil, mine included.

Easy to check, no cost.

08-10-2009	#7
A26B Join Date: Dec 2003 Location: Arcadia, OK Posts: 3,399	Re: spark plugs for a full top end ported engine Johnny, A "weak" spark will show up more as a "miss" when the engine is under load such as 65 in 6th gear, than it will at higher revs or at an idle. It's not a dead cylinder problem until it's under a load like you described. When you check spark, put an old plug in a plug wire, lay it on the plenum & start the engine. It should jump a nice, blue spark 3/4"~1" as you pull the plug away from the engine. If you see an orange spark, it's weak. I have personally seen at least 3, single cylinder, weak spark issues fixed by replacing the coil, mine included. Easy to check, no cost. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.