MPG drop after spark plug change

Ok So needless to say I'm a little confused. I bought some new denso plugs from the stealership, checked the gap on one and it was between .044 and .043. I assumed that the rest were pre-gapped as well. Before the switch I got 150 miles in the first half tank (this was right after cleaning the mass air sensor and replacing the fuel filter). After the plug replacement I'll be lucky to get 125 miles in the first half-tank.

Has anyone else had this experience? Did I screw up leaving the gap at .044? (I keep reading conflicting opinions on the proper gap.) Did I screw up assuming that they were all gapped correctly since i bought them from the dealer? Could it be a vacuum leak from not putting something back on right? (I triple checked everything but mistakes happen.)

I could really use some outside opinions on this. I'm approaching critical frustration mass.

 

are they the right plugs? dual ground electrodes i mean

 

Shitroc has a good question...the 3.4 DEMANDS dual electrode plugs. If they're correct maybe pull the negative cable off the battery for about 20 minutes, let the ECU recalibrate to all the recent changes. Hope it helps.

 

X2, you may want to disconnect the batery for a couple hours and let the ecm reset, some times it takes a little while to learn how to operate after being cleaned and what not.

 

it should say so on the timeimg belt cover on all 3.4s

 

The stickers under the hood saying you must use twins. And the Haynes book. And Toyota's service manual.

 

I bought them from the dealer, for the tacoma v6. Dual electrode, yada yada. If these aren't the right ones then I'm going to have to hurt the parts guy at the dealer.

 

If Toyota found that it was important enough to put stickers under the hood and make notes in the service manual thatn more thanlikely it is important. I doubt it would harm the engine but its definitly not the best for performance.

 

Those are the right ones.

 

Remember this as well.....ALWAYS check spark plug gap.....always. none that I've. Changed have been pregapped at all.

 

The factory that makes the right ones probably dosn't exsist any more so he sold you chinesse plugs instead.........

 

Meaning the gap is set at the factory. But like Will said it's for sure still worth re-checking. Are you getting the engine check light on? If the gaps were excessive you'd have a miss and the ECU should pick that up and light the light. If the gaps are too small you won't lite all the fuel mixture and fuel economy and power will suffer.

 

I didnt think you were supposed to gap the dual conductor type because of risk of damaging the tip? Or is this just for the iridium type plugs?

 

That's the funny thing. It runs very smoothly. When Driving around town I can keep my RPM's under 2000. If anything it's easier to run at lower RPM's after the replacement.

So no there's no check engine light and no loss of power.

Also How do you gap a dual electrode plug? It seems like it will be rather hard because the electrodes aren't flat on the tip side. They are concave, so you can't get a regular gap tool in there.

 

you gap them as normal because the tips are flat and slide right into the gap tool.

 

ah ok. good to know

 

thanks for all the input guys. I'll check my gaps and then reset me ECU.

 

Sorry to post to a 9 month old thread. Are these dual electrode b/c you have a 2002?

My 2008 did not have dual electrode.

 

I would of checked the gap on all the plugs and .043 and .044 I don't think would effect that much that being said I would of gaped all the plugs to spec's.

 

I assume so.