Ignition/MPG issue - Toyota Nation Forum : Toyota Car and Truck Forums

bdy0003 · 02-15-2010, 01:34 AM

What I did: replaced my stock spark plug wires (Sumimotos) with NGK ones, seafoam brake booster and gas tank --> MPG dropped dramatically (dont have a numerical value since I didnt pump up) What I did today: Put back my stock spark plug wires --> went 40 miles, the rate of the needle dropping is less What could be wrong? BTW, I have bosch plugs, still going strong after 47k. Things that I think that might be wrong: bad wires, plugs corroded, O2 sensor fouled

llcoolpass · 02-15-2010, 02:36 AM

less compression

vacuum leak

all in your head

hill8570 · 02-15-2010, 11:56 AM

Check the resistance of all the new wires and all the old wires. Assuming it's not just in your head (I don't trust any MPG data that isn't fill-to-fill), the NGK wires might have resistance that is too high for the Botch plugs. High resistance=weak spark=bad mileage. May have also fouled your plugs running that Seafoam crap through your system, but that would effect both sets of wires equally.

bdy0003 · 02-15-2010, 01:57 PM

Sorry, I'm not very literate when it comes to electronics. I tested my NGKs. My multimeter is set at 200K. #4 is 3.2, #3 is 4.6, #2 is 4.7, #1 is 5.8. Looking at the manual, it says the cords should be 25K ohms or less, so I dont think the wires are bad. I was looking at the NGKs connection to the plugs and noticed they have a smaller surface area than the sumimotos. Could this be to blame? I havent checked the resistance of my stock wires yet.

Quote:

Originally Posted by hill8570

Check the resistance of all the new wires and all the old wires. Assuming it's not just in your head (I don't trust any MPG data that isn't fill-to-fill), the NGK wires might have resistance that is too high for the Botch plugs. High resistance=weak spark=bad mileage. May have also fouled your plugs running that Seafoam crap through your system, but that would effect both sets of wires equally.