View Full Version : 93 SDV 4.9 spark plug replacement post mortem (can't edit other thread)

12-28-11, 05:08 PM
I was able to get the plus/wires/cap/rotor changed out today on my 93 SDV 4.9 that just turned over 100K.

The front 4 were not difficult. The sound of cracking porcelain was a little concerning but just told me that I wasn't centered on the plug and to slow down. Front 4 plugs were done in 15 minutes.

TIP: when doing the rear plugs, remove the strut crossbar. It will make access 100X easier. Don't remove the strut mounting bolts, take the bolts out of the cross bar. There will be a shim that falls out on each side so be ready to catch that. Prepare yourself for breaking the hooked shaped plastic piece that holds the heater hose at the center of the engine. I just drilled a hole in the piece that was left and zip tied it in place.

Plug #8 was probably the hardest to swap out due to the transmission dip stick tube is right there.

The wire holders were the biggest pains in the ass of the entire job. On the firewall side there are 3 holders. Undo the one by cylinder 8 first so you know how to do it on the other 2. they suck.

Buy some of the corrugated wire protector. the factory stuff will be brittle and fall apart on you.

I wrote the wire number on the new distributor cap and on the wire as I was running it. You can see black sharpie on black rubber.

The end result is my Caddy idles so smooth, I can't feel that it is running. acceleration is smooth and strong although I do have a light ping now that I didn't notice before. I will tank up with mid-grade and see if it goes away, if not, then super.

The original plugs now had a gap of about .080" and a couple of the wires had places where the insulation was missing/broken down.

I used NGK platinum plugs (Advance Auto didn't have Delco's for some reason) and Autolite professional grade wires. The wires are 8mm and look to be good quality.

01-06-12, 11:48 PM
The spark plugs and the water pump are two things that I don't look forward to ever changing on a 4.9 again! And I've done both on two Cads!