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Hello!
So I’ve got 2005 corolla 1.6 (gasoline obviously) and noticed higher fuel consumption a few months ago. As i hooked up my OBD reader I noticed long term fuel trim was noticeably high, 15-16% at idle, but when accelerating it peaks as high as 21-24% and drops to 17-18% at cruising. So first thing I checked was vacuum leaks (even though it didn’t seem like a vacuum leak) and didn’t find any. Next thing i did was clean MAF which I had cleaned before maybe a year ago and so it wasn’t really dirty – did not help. At this point I suspected fuel delivery problem since fuel trims go up under load so I tried cleaning injectors. They weren’t clogged or especially dirty and spray pattern looked fine and so this didn’t really help much (noticed something like 1-2% decrease in LTFT) :angry: . After this I thought of measuring fuel pressure and since Toyota has special connectors in fuel lines and did not have tools to do the job myself, I took it to a service shop :unsure: . It came out as perfectly within specifications (50 psi) :huh: . At this point I was almost out of ideas, but came back to suspecting MAF sensor when I measured air flow volume at WOT. With Torque app I got about 72-73 grams/second of peak volume when WOT at 2nd gear. Now I have read that as thumb rule peak air flow volume should be around 80% of vehicle’s total horse power, and if this is true, as corolla has 110hp it would mean that 72g/s is only 65%~ of that. So does this mean my MAF sensor is reading too low figures, or is that only a result of a problem with my car :huh:? New MAF sensor costs around 150 euros here so I really don’t want to buy that until I’m fairly sure that is the problem. Oh yeah and spark plugs have been changed less than a year ago and inspected every one of them so I don’t believe them to be the problem. What would you suggest I do next? :sick:
And sorry for possible misspellings or grammar mistakes as English isn’t my native language (obviously :P), hope you understood most of it, thanks! 🙂
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Man you were lucky to have such a simple fault and fix 😛 . Anyways I got my new MAF sensor few days ago and been driving for a weekend now, BIG improvement to fuel trims! Now LTFT stays at idle 4.7% but there is still the problem when I accelerate, it peaks up to 12-13% and at cruising speed stays around 7-8%. What could still cause that? Should I even try to look further or let it be and see if it got worse over time? I know it will bug the hell out of me if I won’t get it fixed :pinch:
That sounds like progress. It may take a little while for the fuel trims to level out. When I suggested checking for leaks, I was not only suggesting checking for vacuum leaks, I was suggesting checking for leaks in the tube that runs from the MAF sensor to the engine. Any leaks here will upset the MAF sensor reading and can often cause performance and fuel economy issues.
Thanks for the update. Keep us posted if things change.
I just did a post cat O2 sensor in an 06 Corolla today. On test drive, my fuel trims were constantly around 7% max between short term and long term. I’d look at that post cat O2 PID if you can and look for it to stay in the .4 to .7 volt range. If you mash the gas pedal to the floor, your O2 should go full rich and hang out .8 to .9 volts and then on decel, you should be able to bottom out the voltage to nearly 0 volts. That might be a good indicator that your fuel trims are actually where they need to be. If your fuel economy is back where it’s supposed to be, it might be time to stop looking further into this.
Allrighty, gonna have to check that O2 data when I got the time. I’ll be going to countryside tomorrow for a few days so I won’t be able to do any fixing till I get back. By the way Eric, that air tube doesn’t have any hoses connected to it and it goes straight from throttle body to air box (where MAF is also located) so if there were any leaks, they would have come out it as I did the smoke test (I capped the end of the hose with bottle so the smoke and pressure would not escape through that way) and like I said I inspected it thoroughly, took it out and bend it different ways to see if there were any “hidden” cracks or anything. And as for fuel consumption I cannot be sure because it seems like it did not change all that much but that might just be because of weather got much colder here. Also fuel consumption readings on car computer (what ever it is called in English?) are higher than in reality (calculated it by actually filling the tank and dividing with driven distance). Haven’t got a chance to drive full tank yet to see if the actual consumption has decreased or not but will see.
Finally got the time to test that post cat O2 sensor. So, it wants to stay at 0.72 volts while cruising at 2000-2500 rpm, at idle 0.13V and 0.16V at 2000-2500 rpm while stopped. Also does go full rich .8 volts when flooring the pedal and 0V when decelerating. Still haven’t driven full tank so no updates on fuel consumption. Fuel trims haven’t changed either.
That doesn’t seem too far off. You may have gone as far as you can. Something else to consider. If your engine is burning a little oil it can drive the mix a little rich.
It doesn’t really burn much oil, haven’t had to add any within a year and actually should be changing my oil soon. Well I guess I have to settle with this. Big thanks for everyone for your input and help! Cheers! 😛
you can try posting about it here
http://www.toyotanation.com/forum/132-9th-gen-corolla-1st-gen-matrix-2003-2008/
Forum for the 9th gen corolla. Alot of good help there to.
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