First, thanks for all the useful posts. The online Corolla community has some great people, including this other site for routine stuff: http://tinyurl.com/7leqwd7 I've got 116K on my '05 and it's been a dream. I've changed the various filters and oil all the way through (Castrol every 3K) and have started replacing other parts:
The intake manifold gasket was straightforward and solved the P0171 CEL. If you go to a Toyota dealer there are conflicting stock numbers, so make sure to get the orange gasket, which is the improved model. I missed a throttle body vacuum hookup on re-assembly, but the engine reminded me - barely ran & misfired, and I quickly found the problem.
The PCV was easy, and I should have done it much sooner. It was the original. So was the battery, which also got replaced. Serpentine belt was done at 97K. That was a little tight and tricky, but really no problem.
The coolant drain/replacement seemed simple, but even with the engine block drain open an air pocket kept half from draining. I feared the heater core was plugged and didn't want to take a chance - replacing that is an enormous job. I took it to a shop for a full flush and all is well - the heater now works like a flamethrower. Q1: Could cranking the engine a few times have solved this?
I hadn't replaced spark plugs since an earlier vehicle, but that was pretty simple. A caution is that the wiring harness for the ignition coils (spark plug boots) will need to be moved. This is not noted in Haynes or a few online instructions. The harness runs along the rear aspect of the coils and blocks the two on the driver's side from removal. Take off the one bolt and one nut to get a little clearance and you're good. Other than that detail, removing the plugs (slowly and carefully) was no problem. The old plugs were fairly clean but the center electrode was noticeably worn - lost some length. The new ones made a big difference.
The engine sounds much better and almost all is well...but my mileage is off by about 20%. The air filter is good, as is tire inflation. Q2: Any recommendations about this mileage oddity? Thanks!
Last edited by NWCorolla05; 01-02-2012 at 08:09 PM.
Cranking the engine? It's good now because it was properly bled and filled.
Fuel mileage might be restored with a new primary A/F ratio sensor on exhaust manifold. Have you cleaned your MAF/IAT sensor on intake? Was your transmission fluid replaced at 60000 miles?
Please forgive our misinformed little buddy south of the border... 2005+ Corolla 1ZZ-FE with DBW have an Air/Fuel ratio sensor on exhaust manifold, instead of an oxygen sensor like on my 2004.
Thank you that is interesting, since an oxygen sensor is used to determine air/fuel ratio imperfections.
So upon further review I did a little research and for those interested, here is a paragraph describing the difference between the two:
What distinguishes Air-fuel ratio sensors from regular O2 sensors is that the AFRS is what is known as a wide range O2 sensor whereas the basic O2 sensor is a narrow range sensor. It can detect a wider range of air/fuel ratios than the basic O2 sensor. Also, the AFRS has a little bit more circuitry to enable it to detect more minute variations in the exhaust system air content (more sensitive than the O2 sensor). Therefore, it is able to make better adjustments thru the ECM to add or subtract fuel to produce a better mix of air/fuel to maximize efficiency and minimize emissions.
I wonder how well the shop did. You think some coolant was trapped by an air pocket, preventing a complete draining? There may be some coolant left above closed thermostat if it's not removed as well.
You mean your air/fuel ratio sensor on exhaust manifold. Even without throwing a CEL, it does wear out, degrade from contamination and weaken progressively over time, becoming slightly less responsive, which gradually affects fuel efficiency and overall performance. Their service life is normally up to 100000 miles.
Sensor may be seized on tight. It'll be easier to loosen while exhaust manifold is still warm. You should be able to slip the closed end of a 7/8" wrench over the connector if you unplug it first. There are also sensor sockets that could help.
Did the mileage drop off immediately after the the tune-up?
Did you use Toyota Parts for everything?
If not what parts did you use that were non-Toyota?
Were there any changes to conditions after the Tune-up (i.e. noticeably colder mornings, longer stop and go etc.) as 20% is a huge difference in fuel economy. On a Corolla that is around a good 6-8 MPG depending on driver.
The only thing I could think of is something is off on the plug side of things (gap, type, heat range) without the above answered.
The mileage had been fading a little beforehand, but became much more noticeable after the plug change. I once had a similar problem with an O2 sensor on a Mazda Protege, so the AFRS sensor will likely solve the mileage problem.
The RockAuto link that invader posted above was about half the retail price for a new Denso OEM sensor - a great parts site to know about.
The mileage had been fading a little beforehand, but became much more noticeable after the plug change. I once had a similar problem with an O2 sensor on a Mazda Protege, so the AFRS sensor will likely solve the mileage problem.
The RockAuto link that invader posted above was about half the retail price for a new Denso OEM sensor - a great parts site to know about.
Be careful as RockAuto tends to be a little high on shipping. Amazon has it for just a bit cheaper but with free shipping! CLICK HERE
Be careful as RockAuto tends to be a little high on shipping. Amazon has it for just a bit cheaper but with free shipping! CLICK HERE
Thanks for the heads-up, but I'm OK with Rock Auto. When I called them (toll-free) with a question, after pressing one button, a real human being picked up the phone and was knowledgeable and courteous. That's pretty frickin' cool these days. I like their return policy, too. The shipping was only a couple of bucks ($2.83 for First Class USPS), so that was no biggie.
I closed my account with Amazon a few years ago because their labor practices are awful, CEO Jeff Bezos (worth $18bn) is a poor example of humanity, and the corporation's level of charitable giving in the Seattle area is a bad joke - has been for years. I don't want to encourage any of that.
Good move... You also won't find out that some mistery Amazon UK account used your credit card number to purchase items shipped to some European address, and then have your credit company open a fraud investigation and give you a new card...
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