I'm about to do some work on my '03 Disco II this weekend... new plugs, magnecor wires, four O2 sensors, and a throttle body gasket are somewhere between here and Utah as I write this. Now, I've been driving around with P0150 for almost a year, and I've got a nice black ring around my exhaust pipe (and about 10 MPG) to show for it. I figure running the way that it has been, there's plenty of carbon buildup in there, so I was also thinking of doing the seafoam treatment. My question is, what would you suggest as the proper order to replace all of these parts?

Part of me says do the seafoam first, then after the exhaust is clean again, replace the plugs, wires, and O2 sensors. The thought behind this is that burning all of that crap out can't be good for the rest of the system, so do it while the soon-to-be-replaced parts are still in place.

The other part of me says replace the wires and plugs first, then do the seafoam, because I'm gonna need the extra oomph in order to effectively remove the hot mess that's surely in there.

There's not really a part that says replace plugs, wires, and sensors before the seafoam, because I figure that's just asking for the waste products to muck up four brand new O2 sensors.

Thoughts?

 

Why have you been running around with a 150 on, that has cost you lots of money in bad gas mileage and possible cat issues.
Here is the list, follow it to the letter.
1 Oil filter, K&N 3001 or Mobil 1- 301
1 Factory air filter
6 Qts. of engine oil
2 feet of 3/16th vacuum tube
2 feet of 5/16th vacuum tube
12 Qts. of ATF
7 Qts. of 80/90W synthetic gear oil, 85W/140 for HD use
3 Pints of synthetic DOT 4 Brake fluid
2 Qts of synthetic Power steering fluid
2 Gallons of OAT, orange coolant, also called DexCool
1 Bottle of Lucas Power Steering additive
1 Bottle of Lucas Transmission additive
1 Can of Spray Carb. Spray
1 Can Of Brake cleaner
8 Spark Plugs, I use Bosch Platinum Plus 4's
1 Set of Magnacor 8mm plug wires
1 Serpentine belt
2 Bottles of SeaFoam gas additive
1 T/Stat
1 bottle of WaterWetter or Purple Ice
Hoses and belts, as necessary

60,000 Mile Service or Major Service for High Mileage Used Vehicle just purchased

Bleed the brakes
Flush and change the power steering fluid adding one bottle of additive
Service the tranny adding one bottle of additive
Change the coolant and t/stat
Do an engine flush before changing the oil
Do an induction cleaning
Clean the throttle body
Add fuel additive to full gas tank
Change both of the diffs fluid
Change the t/case oil
Replace the plugs and wires
Replace the air filter
Lube all the drive shaft grease fitting including the 2 slip shafts
Do full inspection of brakes, hoses, bushings etc.

Hopefully I didn't leave anything out.