Plug Wires

[cracker]

My 91 with 53K miles has started to misfire under load. When in Netrual and accelerating the mis is not noticeable, but in Drive, holding the brake and accelerating it,s misses like crazy. This started as an occasional misfire during acceleration and has gotten progresively worse over 1500 miles or so. I intend to start by replaceing the plugs , fuel filter and then plug wires, in that order. If I replace the plug wires, I would like a replacement set just like the originals, same boots, insulators, color lenght etc. Does anyone know were they can be purchased?

91 Reatta Conv

91 Reatta Coupe

85 Riv Conv, Turbo

71 Corvette BB Conv

04 Corvette Conv

[charlie1]

If you want EXACT replacement you may have to contact Jim Finn for a good used set. Perhaps you can find the bad ONE and Jim can help you out. I have a 1989 and wanted the EXACT same replacement. The color is light gray. Had to settle for a AC Delco set.

Good Luck

[rjfranken]

Save the coil-pack for last. You can test the wires by spraying (squirting with a spray bottle) the wires and coil-pack areas. A bad spot will then show up as a major miss and you can hear it too. Also on a moist day the spark leak will show up. Coil-packs can have an internal leak and for some reason under load makes for more resistance therefore the leak is more prominent. A bad plug will also fail under load more so. Wires leak the spark out. Look up Padgetts coil-pack upgrade if you end up going down that road. (I love my car!)

[Ronnie]

Thanks for the info on diagnosing spark plug wires. I learn something new every day!

[NTX5467]

When replacing the plugs, make sure they are gapped to specs YOURSELF. A flaky or fouled plug might be more common than a spark plug wire issue. When you load the engine against the brake at "fast idle", it raises the cylinder pressure in the cylinder which makes it harder for the spark to jump the gap in the spark plug . . .which puts more stress on the plug wires at the same time. Therefore, START with the spark plugs.

The fuel filter would have little effect . . .unless it was really clogged up. If it was that bad, you would be experiencing "extended crank time" as the fuel system pressure slowly increased to the minimum required to fire the injectors. Then, it would have "low power" in other operational modes, not a "miss" per se.

You might check the intake manifold gaskets, for good measure. I suspect that if you have a noticeable operational issue, there should be a Check Engine code, too? You might also get somebody to do diagnostics and see if all of the injectors are firing correctly?

To me, getting a used plug wire can be trouble, with all due respect, unless you are chasing complete originality or similar. Shop around for a quality OEM-spec set -- key word "OEM-spec" set -- rather than "loss leader house brands" at the auto supply. To me, an ACDelco set would be the first place to look.

When was the last time you bought gas for the vehicle? Possibility of seasonal change and the resultant change in fuel blends having an effect?

Seems like some of those engines had issues with EGR valves and their controls? How is idle quality? Still, should be some codes to check!

Just some thoughts,

NTX5467

[padgett]

Good place to look is any plug lead resting on top of an exhaust manifold (have seen more often that you would think). Reatta needs at least 8mm leads for a .060" gap.

Most common sympton of a bad wire is one that will run OK up to about 25 mph on a light load then get all cranky if you stand on it. My experience with failing coils has been more "misfire under moderate load at low RPM" but clear if you accelerate hard.