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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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At wot usually sensors are not monitored. Your adding fuel
with the positive fuel trims. what is the front o2 doing at
2500 rpm? more in this link.http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
It seems to be switching between 0.1 and 0.8 volts, but Torque’s diagram isn’t the most accurate so I will attach a screen capture of it here.
o2 signal looks good. Vacuum leaks or MAF. If you unplug the MAF
does the engine run better or worse? It should run worse right away.Yep, unplugging MAF totally stalled engine. If it is a vacuum leak I can’t find it by normal methods (carb cleaner/propane), guess I’m going to need a smoke machine :unsure:
Already checked PCV valve, it was working fine (don’t know if there are more than one) and air filter is fairly new and the problem certainly isn’t lack of air anyways (right?) 😆 but thanks for suggestion.
Also, I kind of forgot to mention one symptom that might or might not be related (because I have had it always) and is somewhat rare. While engine is hot and has been sitting for maybe 15 minutes, sometimes it cranks for longer time (sometimes maybe even 2-3 seconds) and it feels like engine has a little trouble to start right away but like I said it doesn’t do it that often and has been there ever since I bought the car, around 2 years ago. Also if it helps the car has got about 74000 miles on it.
Be sure you cleaned the MAF not the IAT… The IAT is the red bulb that is usually most notable… The MAF sensor wire is down in the sensor itself and hard to see… Cleaning the wrong part can happen….
Based upon what you have said, the MAF is extremely suspect…. Most people don’t notice a problem until something is wrong… You may be just seeing degradation early….
I recommend a new MAF and Toyota Air filter…..
JMHO
-Karl
Yes I got the right part cleaned 😛 although I did that mistake at my first time cleaning it :silly:. But yeah I was also leaning towards MAF. I guess I’ll make some kind of DIY smoke machine myself and try vacuum leaks one last time before buying that horribly expensive maf, I probably don’t want to even consider those aftermarket ones or does anyone know a brand that actually works?
In addition to vacuum leaks, you should also check for any leaks in the air tube that runs from the MAF sensor to the engine. That can also cause issues. There may be useful information here as well.
http://www.ericthecarguy.com/faq/finding-and-fixing-the-causes-of-poor-mpg
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Keep us posted.
Ok so I did a thorough check for leaks with my homemade smoke ‘machine’ (basically a glass jar with metal lid, air connector, hose and mosquito coil bits for smoke B) ) and also inspected the air tube and now I’m 99% sure that there are no vacuum leaks. I placed an order for new MAF sensor from Germany (it was cheaper there than here in Finland) and now just need to wait till it arrives which may take a week or so :dry: I’ll be posting the results then. :cheer:
If you haven’t done so.
I would replace the intake manifold gasket, $7 part, 15 min job. The 9th gen corolla pretty much has a 100% failure rate with those gaskets. It get brittle and leaks. The new revise gasket is orange.
follow this DIY
You have to remove the throttle body to do this, so, it would be a good ideal to clean the throttle body while it is off.
In fact I did replace it maybe 2 years ago when I had a vacuum leak. It turned out not to be leaking which was weird because (I thought) I found leak by carb cleaner when I sprayed around certain spot at intake manifold (down right side, right around gasket area) and I clearly heard engine sound change, repeatedly :huh: . But after changing the gasket I could not believe it, still had vacuum leak. And still spraying the same area caused engine idle to change, but nowhere else. Then I thought of taking off a breather hose which goes to intake manifold and blew air with my mouth in to the hose. I clearly heard the hissing and found the leak to be a cracked hose under throttle body (I think it goes to evap solenoid) also sprayed plenty of carb cleaner there too and did not have any effect on idle. I guess troubleshooting doesn’t always go by the book 😛
[quote=”Brontos” post=111981]In fact I did replace it maybe 2 years ago when I had a vacuum leak. It turned out not to be leaking which was weird because (I thought) I found leak by carb cleaner when I sprayed around certain spot at intake manifold (down right side, right around gasket area) and I clearly heard engine sound change, repeatedly :huh: . But after changing the gasket I could not believe it, still had vacuum leak. And still spraying the same area caused engine idle to change, but nowhere else. Then I thought of taking off a breather hose which goes to intake manifold and blew air with my mouth in to the hose. I clearly heard the hissing and found the leak to be a cracked hose under throttle body (I think it goes to evap solenoid) also sprayed plenty of carb cleaner there too and did not have any effect on idle. I guess troubleshooting doesn’t always go by the book :P[/quote]
My 07 corolla, was throwing a P0171 code a few months ago. Already replaced the intake manifold gasket, so i though it wouldn’t be a vac leak. So i cleaned the MAF sensor. Was about to replace the O2 sensor. But before i did that, i decided check for a vac leak. Took the engine cover off. And the vacuum line was disconnected. was probaly like that for a while. Got some new hose clamps on them now wont come off now lol
The hose to the left of the oil cap
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