6 miles to the gallon blues
 

So December i came home for the holidays after not having my car for a while and did a tune up on my disco: switched over to full synthetic, oil filter, air filter, spark plugs, plug wires, fuel filter, induction cleaning, and put seafoam in the oil as well. I immediately started getting misfire codes, and horrible gas mileage. I was getting misfire codes, but no o2 sensor codes. I had switched from regular spark plugs to bosch platinum +4s, but used a set of advance auto parts plug wires, so i got another set of wires, this time magnecor, which solved the misfire problems, but not the gas mileage woes, so i had the o2 sensors replaced over president's day weekend, and about 45 min. later driving home on the interstate, the CEL came on giving me o2 sensor codes, and my gas mileage went from an already bad of about 9-10 mpg to now around 6 mpg. I called the mechanic and i'm going back friday to have him redo the job, but for some reason i feel like something else might be going on? The drop in gas mileage wasn't a gradual decrease either, it happened immediately after i did the tune up. Is there something i could have done wrong? Is there something else i should suggest the mechanic to look at? Thanks

98 diso le
141300 miles

what are the 02 codes are you getting? what kind of air filter did you put in? k&n or the paper type?

when i checked immed. after getting it the first time, it was something o2 related, but can't remember, so i just went out, and wow...a whole lot more codes
p0130
p0133
p1179
p1177
p0304
p1177 pending
p1158 pending


and i'm using a paper filter for the last couple months, but had been using a k&n when i first got it up until a couple months a go, so just under 2 years

also, i forgot to add, the engine doesn't idle as well as it used to, when i start it sometimes, it almost feels like its going to cut off for about two seconds and then the rpms go back up to where it should be.....

Dump those spark plugs and go back to the cheap copper plugs.
Some engines wont like certain plugs.

should i also go back to the advance auto parts plug wires as well?

No, keep the Magnecor plug wires, just switch plugs.

Thanks Spike, i'm gonna switch them out tomorrow.

Add another for swapping plugs. You can run 8MM wires on anything, but +4's will foul on 7MM wires.

i ran 7mm with +4's for 8 months with no problems.

so i just put in some regular spark plugs and now there's a ticking coming from the driver side, any ideas? I kept the advance auto spark plug wires that i took out, cause they were brand new, so i'm going to switch out the magnecor wires and see if that does anything, just wanted to know if you guys might know exactly what the ticking could be, after changing spark plugs