Just threw a new set of NGK Laser Platinum plugs and a fuel filter in this past weekend. Instead of getting slightly better gas mileage, it dropped from 25 mpg or so to around 18 mpg with increased sluggishness. Anybody ever get a bad set of plugs from NGK??

You know what? Mine did that too. Well, except for the slugishness. It got mo powah when I did it. I haven't reset my ECU, though. I'm gunna try that and see how it goes.

You just unhook the battery to reset the ECU?

So I didn't search well enough before posting. Found a recommended reset procedure as:

 

1) disconnect negative for 30 min

2) idle for 15

3) then drive, shut off

 

Will give it a shot.

Unhook and press brake pedal.

 

Are you sure the wires are secure in place? Maybe need for dielectric grease for the connections? Did you check the resistance of plugs and cables?

 

Keep up posted, I am planning to put the laser platinum in soon.

10-4. Checked and rechecked physical connections. All lubed up with dielectric grease. Just got new wires within the past year, but will be rechecking them with the multimeter this evening after work.

 

Resistances should be in the hundredths of an ohm, correct?

Resistance will probably be 10 to 20 K Ohms. As long as the four wires are relatively close to each other, no problem.

I didn't use dielectric grease or check the wires, so mine might be unrelated. I might check tonight if it's not too wet out and I can find my dad's multimeter. Too bad my good one's 90 miles away.

 

I second the 10-20kOhms motion, especially the "They should all be roughly the same" part.

Got between 9.4 and 10.0 KOhms for the wires so they all look good. What is an acceptable range on the plugs?? The measurement is made from the wire boot end to the probe I assume.

I'm actually having a similar problem with my Probe. After changing the fuel filter I've noticed decreased MPG (not as bad as yours though). I reset the ECU tonight hoping it fixes the issue.

Got between 9.4 and 10.0 KOhms for the wires so they all look good. What is an acceptable range on the plugs?? The measurement is made from the wire boot end to the probe I assume.

 

NGK plugs read 5-6 kohm or so.

Any follow up on this?

 

And BTW, according to FSM (in kohms I presume):

#1 cord: 5.6 — 10.6

#2 cord: 7.3 — 13.7

#3 cord: 5.9 — 11.1

#4 cord: 7.3 — 13.7

The resistance of the plugs themselves will be completely open.

Been away from the computer for awhile so haven't been able to give an update. Anyways, turns out the problem was in my tires. Had just bought new tires two weeks ago and for some reason three were at 28 and the fourth was at 22. Thought I might have picked up a nail, etc in the lower one over the weekend but couldn't find anything. It was really starting to annoy me since everything checked out ok and it was running fine except for the mileage drop. After airing them back up, I'm back at about 24-25 mpg.

Been away from the computer for awhile so haven't been able to give an update. Anyways, turns out the problem was in my tires. Had just bought new tires two weeks ago and for some reason three were at 28 and the fourth was at 22. Thought I might have picked up a nail, etc in the lower one over the weekend but couldn't find anything. It was really starting to annoy me since everything checked out ok and it was running fine except for the mileage drop. After airing them back up, I'm back at about 24-25 mpg.

 

Thanks!

Holy crap!!! Your mileage dropped from 24 mpg to 18 just from low tires?! I would expect a little maybe, but yeesh. Maybe I'll try inflating mine a bit more than normal recently and see if that picks up the mileage a bit.

Yeah, got em back up to 32, and they roll nicely.