Fuel Economy dropped after spark plugs replaced

the MAF is a heated wire that measures how much air is flowing into the intake. if it is dirty the wire is covered and thus will run hot, the ECU adjusts for this.

Now you clean it and the film of dirt is gone, it will run cooler for the same amount of air coming in the engine. The ECU interprets this as more/faster air flow and thus has to add more fuel (richen) to compensate. Have you tried unplugging the 12V battery and allowing the ECU to reset?

 

No I will do that for sure.

 

No change after disconnecting the battery. I didn't think it would since I didn't see why change after cleaning the MAF. Just after the spark plugs. Now I have tried just about everything to get my 10+ mpg back.

 

What are your tire pressures at? Possible low tire pressure?

 

Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat

 

No not low tire pressure. 45-50 psi. Always run that on my vehicles, tires last much longer and get better mpg. I have read that. Like I said I changed my spark plugs and lost 10+ mpg. No engine codes to signify I damaged any wires. But it is getting mpg that seems to be 3 cylinders instead of 4. Dropped about 10-15. If you do the math it's almost right on for a 25% decrease.

 

When you removed the new plugs did you notice any difference between them? (carbon, ash, oil, etc)

Might try the PCV valve for grins.

Was that 400k all on the same HV battery?

 

The plugs all look really good. They all look new yet. That's why I don't know about the potential wire issue since none look different. Yes same hybrid battery. I never replaced the 12V so there is a chance that was original also.

 

if it feels like it is missing something is wrong. You may have damaged the low voltage wire harness for the coils. Any codes for misfire? Are the plugs the same heat range as the original? Torqued properly? What did you clean the MAF with

 

I do not have any codes, both sets of plugs are original heat range plugs. As far as torque they should be right around the recommended torque. Gapped the NGK's not the Densos. Didn't want to change them when they were getting over 50 mpg the way they were. I used MAF sensor cleaner.

Today on my way home from work it was 32 degrees F and with no warm up and just leaving from work it was averaging over 50 mpg at 60mph for the first 4 miles or so after 4-5 miles of it driving really good in town at 30-45 mph. Averaging around 60 mpg in town. Then it felt like it lost some power on the highway and dropped from over 50 mpg to 38-42.