Fuel Economy After Repair

Hey all,

I am struggling to diagnose a problem that came up after I replaced the valve covers in a 2006 Tacoma v6 4wd automatic. Fuel economy went from 17-21 to now getting more like 11-13mpg.

I mistakenly switched vacuum hoses leading to the break booster and the canister purge valve thingy. I ran the engine at idle for a while not knowing that was an issue until I tried to roll. When I had no break booster I shut it down and fixed those hoses. From there I had a PO171 and PO174 code pop on so I replaced all the OEM air lines to have hose clamps to help prevent air leaks and cleaned off the MAF. From there my idle went from (at temp) 1100 rpm down to 450 rpm and the CEL shut off. I then changed out my air filter again thinking it was getting choked out. Idle went back up to 1100 rpm and I still have a fuel econ problem.

Any other suggestions would be greatly appreciated, I am trying to avoid tearing everything down again and checking... but if that is the solution, that is the solution.

PS: I replaced the canister purge valve because it was no longer opening up at all, how would one test if the unit is working or not? I also need to replace my coolant but do not think that would lead to the economy issues. I currently have no CEL on. Thank you all for reading.

 

So your warm idle is at 1100 rpm?
How changing the air filter caused this is beyond me.
Is the MAF sensor dirty?

Do you have any pending codes?

 

I have no pending codes, MAF is clean as a whistle now that I have cleaned it.

 

Is the hose from the air cleaner box (back side) to the fuel pressure regulator connected?

 

Valve cover replacement, intake was off.

 

I will give the hose going to the fuel pressure regulator a look tomorrow. I wasn't able to find anything after about a half an hour of searching today, do you know where I could find stock photos of the engine bay so I could determine if maybe I still have a hose that is not where it should be?

 

There's a vacuum line diagram under the hood. On a sticker.
Somewhere on here, I have a picture of mine.

Let me see if I can find it.

 

I am definitely going to be checking this tomorrow then, would you agree that it seems to be a fuel pressure regulator line? Could it still possible be a vacuum leak? I am already so thankful for your responses all!

 

The hose was connected, but loose. I tightened it down, regapped the spark plugs (new as of 5,000 miles ago) put dielectric grease in the plugs and now it's idling better but sounding a bit choppy. Like a chugga chugga-chugga chugga of a trail rolling bye. Currently idling at 550 at temp with air completely off. When put in gear it sounds like it wants to stall now. Same thing I had when I changed the air filter out.

I guess not I have to drive to find out if that was the solution

 

Have you cleaned the throttle body?

 

No, but I probably should, do not know if that has been done yet

 

For anyone referencing this thread later, it was the fuel pressure regulator line. I had it pressed on half-way. When I put it all the way on my issues were resolved. Thanks all.