: What would a gas coating on a plug mean?

06-25-04, 01:09 PM
1994 cadillac Deville Concourse just got a tune up yesterday. 182,000 miles. Changed the plugs and they were also pure white with the yellowing color where they meet the wires. I did have what looked like alot of gas coated on the #6 plug. Changed the plugs because I was getting a rough ride. What would a gas coating on a plug mean?

06-25-04, 01:15 PM
If the plug looked wet or had liquid fuel on it when removed then likely the injector for that cylinder is leaking or stuck open.... THAT would be the source of the rough idle. Replace that injector to remedy. I would pull that plug again and look at it. If it is gas fouled then look at the injector. If the plug runs in the engine while it is gas fouled it can ruin the plug even though it looks perfectly fine after the injector/over fueling problem is repaired. When the spark arcs thru the liquid gas on the plug porcelean during the misfire it can often etch a small, invisible line or "crack" into the porcelean that will cause misfiring in the future. After you determine the source of the overfueling for that cylinder replace just that one plug to avoid any driveablity problems in the future.

06-25-04, 01:23 PM
Awesome, thanks so much for that information. This site has thus far saved me several hundred $$ by helping me do things myself that I would have never done before. I really love my 94 caddy and althugh it seems like it is nickle and diming me, it is still less to maintain than a car payment and the bottom line is that I just really love this car. Wife wants a new one and that is our current battle lol.

Can I pull the fuel injector and clean it or replace it myself or is this something recommended for a real mechanic rather than a wannabe?


06-25-04, 03:25 PM
Changing the injector is pretty simple. On your engine you will have to remove the perimeter row of screws that hold the silver top cover on the intake manifold to get to the injector. On the 93/94 Northstars the injectors are inside the intake itself so the top cover has to be removed. Do not remove the center 4 recessed bolts....just the row of screws around the perimeter of the manifold. Pull the fuel rail up to access the injector and R&R it. Put the top cover back on and you're done.

When you have the manifold top cover off make sure and do NOT start or crank the engine as the intake manifold cover is off and the engine will run away as it is unthrottled.

When you have the injector replaced and the fuel rail back into position, however, it would be a good idea to check for fuel leaks before reinstalling the top cover. Have someone turn the key on several times to pressurize the fuel rail (the fuel pump will run when the key is first turned on) while you watch the manifold with the cover off for fuel leaks. Do NOT crank or start the engine.....just turn the key on to energize the fuel pump. Watch the fuel rail, the injector that you replaced, the fuel fittings and the vacuum nipple on the fuel pressure regulator for any sign of fuel leaking when the key is turned on. If you see any at all, find the source and repair. There shouldn't be any fuel leaking anywhere with the top cover off and the system energized.