MAF Sensor changed, using more fuel - Toyota Nation Forum : Toyota Car and Truck Forums

canuuk01 · 09-20-2011, 12:42 PM

Just passed 20,400 miles and the MAF sensor failed. It was easy to diagnose and have changed out, but in the few days since, I've noticed it seems to be using up fuel much quicker. It's definitely improved the performance, but burning up the gas as well. Is this normal, or is there a way to "reset" it ?

Gary
2008 Highlander Sport

jeffs3820 · 09-20-2011, 01:44 PM

Disconnecting the battery for about a minute will basically force the computer to re-learn your driving habits. As far as the mixture accuracy, that is determined by the O2 sensors so unless you have a check engine light one can assume the mixture is within tolerance.

canuuk01 · 09-20-2011, 09:27 PM

Thanks, I'll try the battery disconnect and see if it makes a difference tomorrow.

Gary

AVConsult · 09-20-2011, 10:42 PM

The quickest way to check it out is a scan tool--the truck is under warranty, yes? The air flow and long term fuel trim metrics will tattle if somethings amiss.

canuuk01 · 09-21-2011, 08:32 AM

I'm in Canada, and my '08 HL Sport is an American model, so that poses problems for the local (Cdn) Toyota dealer who will not warranty until I have a copy from the previous Toyota dealer that there were no issue's, etc., when the vehicle was transferred into Canada. The dealer in Vancouver is dragging their feet, so meanwhile no warranty coverage. The MAF sensor was approx $180.00 installed, and certainly improves the performance, but now I'm really using the gas, even though I'm trying to be careful on the gas pedal.

Gary

AVConsult · 09-21-2011, 01:34 PM

Can we step back briefly to the exact symptoms re: the original MAF sensor failure (a very very rare thing)? CEL? Scan codes?

A few free things to check; valve cover breather hose is connected to the air plenum, vapor recovery canister hose is connected, all the throttle body ducting is snug, MAF sensor O-ring wasn't compromised (a recent post)...essentially look for air leaks downstream from MAF sensor.

canuuk01 · 09-22-2011, 01:56 PM

I do not know the codes, but when the vehicle died on me, I started it up again, and the orange triangle came up on the dash, followed by the engine light, then the VSC, and the VSC vehicle icon. The HL took two tries to start, then started up, and I went straight to the garage. They could not clear the codes, and tried using an MAF sensor cleaner which made no difference. A new MAF sensor was picked up at Toyota and as soon as it was installed, they could clear the codes, and it ran great. The funny thing was, there was no prior warning .... it just quit when I slowed down to enter a parking space. The mechanic suggested a short grounding out on the "platinum" line in the MAF plug ?

Lots of "go", but looks like I'm using more fuel. I just filled up and will check mileage in the next few days.

Gary

AVConsult · 09-22-2011, 10:13 PM

hmmm, do you still have the old MAF? Can you take close and well lit macro photos of the sense wires?

It's possible that MAF was faulty/miscalibrated from the start and finally drifted so far that ECU couldn't manage, or a badly attached sensor wire that gave way, in which case the ECU eventually flagged it and went into "limp home" mode.

A miscalculated MAF sure would effect gas mileage. If it read chronically low, the thing would want run lean all the time, with the ECU maybe confusing that with high altitude operation, where engines tend to use less fuel....and have less power as well. Just guesses....