'00 Camry LE 5SFE: Unexplinable loss of fuel economy

[DougB]

Hi there,

I recently did a whole bunch of maintenance on my 2000 Camry.
See this post for details: '00 Camry LE 5SFE: Misses @ idle, hesitates on initial acceleration

I typically drive the car back and forth to school every day ~2mi each way in town with the occasional 75 mile interstate trip to Indianapolis and back. Over the last month, I've noticed my fuel economy decrease from its usual 30-35mpg to 22-27mpg and most recently as of today I calculated 18mph. These numbers have been on the straight decline and I don't know how to explain it. I detect no fuel leaks and there are no codes being thrown.

32mpg = average fuel economy (city/hwy)
27mpg = started to notice something fishy about a month ago (mixed city/hwy driving)
22mpg = I believed there might be a problem blossoming (mixed city/hwy driving)
18mph = Today. Something is definitely wrong (city driving)

This situation is a semi-emergency as I'm supposed to make the 1000mi+ trip to Denver and back over the weekend for a conference. Flying there is not an option.

The only other thing that I can think of is that the car threw a code about a month ago for the charcoal canister. I reset the computer (unhooked the battery cable for ~10min) to see if it was a false positive and the issue has not shown up since. The only other thing that I could think of is that it might be a stuck injector... but there aren't any codes.

The car's performance is otherwise excellent!

After searching, my case seems eerily similar to this:
2002 XLS Sudden loss of gas mileage

Wondering if there's any insight that can be shown on the situation? 18mpg is crazy bad fuel economy!

TIA!

-DougB

[fenixus]

check it again on 100% highway trip. I'm sure you will see something under 30mpg again.

my 2000 5s-fe (california specs, automatic) sucks terribly in city driving on short distances especially in cold weather, last time I got 18MPG (100% city driving, 2 mile trips one way), but I believe that was because of timing belt tensioner going bad (replaced already and reset the timing 2 weeks ago).

besides that if you have no codes, you may try a different oil grade, presumably synthetic should give you better MPG slightly, especially if you try something newer like Mobil1 0W-30 Advanced Economy (compatible with 5W-30), which improves the cold start MPG (first 10 minutes of driving).

Another possibility is your oxygen sensors (or Air Fuel Ratio sensors in California specs) are going worn out old and sloppy and screw up fuel trims.

You also might have a slight vacuum leak throwing the trims off (I have this minor problem and can't find the bitch).

another idea is that your spark plugs are worn out, when were they replaced for the last time?

also you can run a can of fuel system cleaner through the system, there is lots of them, but best results I had so far with Sea Foam and Chevron Techron 20oz. there is also something which I haven't tried but thinking of it - CRC Emissions Formula.

[Solid_Koolaid]

The fact that engine performance seems unaffected is rather strange... but :

- spark plugs ? (condition, gap, tight, ...)
- distributor ? (oxidation, wear, timing (!!), ...)
- ... eh ... when engine is well warmed up, any unburnt gas smell at the exhaust ?
- How old is the timing belt ? even a slight shift in engine timing could mean reduced fuel economy while still having good (even sometime slightly better performance, especially since valve timing on the 5SFE is very very conservative)

I'd look for other causes such as brake drag, transmission, ...

- Lift the car and check if you can turn all wheels by hand without much resistance (put the car in neutral)

- Auto tranny ? Any slipping, "loose" feeling when accelerating, any usual gear engagement/change anomaly ?


Good luck on this one

EDIT : After seeing fenixus' post, I agree on the possibility of O2 sensor getting worn out, check resistance as per manual. vacuum leak too. Actually all A/F ratio related possibilities

EDIT 2 : And I agree with fenixus too on the 5SFE getting crappy MPG on cold & short trips... used to have one in a '90 Celica.

[DougB]

Plugs & wires are new as of August. Changed the oil over the weekend. Tire pressure is steady on all 4s @ 33psi and tires are new as of May. Injectors have been cleaned. New air filter and fuel filter. All new belts, etc. New H2O pump and thermostat. Intake has been cleaned. Throttle cleaned. (most of this is in the first link I posted)

I can't feel anything like brake drag. Checked the A/T fluid level and it's a little high... but if there was any overfilling, it would've been done by the dealer when I went in for an alignment the other week. A/T is otherwise strong (like new) - good clean shifts.

Don't have the time to take it for a 100% highway run before my 2000mi trip tomorrow.

Honestly, I can't think of anything that would reduce fuel economy to 18mpg without gas physically leaking out of the vehicle.

[fenixus]

might be worth to invest in an OBD2 cable for laptop, cheap like $20-40 off ebay:
http://shop.ebay.com/i.html?_nkw=obd...1&_from=&_ipg=

so you can check the oxygen sensors now as rest seems covered.

and see what computer says (might be nothing interesting though)... besides that ... was the timing belt tensioner changed with belt and pump?

can't think of much more besides the fact that 5s-fe fuel economy simply sucks on short cold start trips... it won't get any higher than 20MPG even on warm engine in city (28MPG on highway per that site) anyways (updated EPA says that)...

http://www.fueleconomy.gov/feg/findacar.htm

[JohnGD]

What code did it throw? Autozone can read them free in your state I'm sure.

You can also pull the EFI fuse for a minute. That way you don't need to reset the radio station and clock.

Originally Posted by DougB

The only other thing that I can think of is that the car threw a code about a month ago for the charcoal canister. I reset the computer (unhooked the battery cable for ~10min) to see if it was a false positive and the issue has not shown up since. The only other thing that I could think of is that it might be a stuck injector... but there aren't any codes.

[islandboy57]

Originally Posted by DougB

I typically drive the car back and forth to school every day ~2mi each way in town with the occasional 75 mile interstate trip to Indianapolis and back.

32mpg = average fuel economy (city/hwy)
27mpg = started to notice something fishy about a month ago (mixed city/hwy driving)
22mpg = I believed there might be a problem blossoming (mixed city/hwy driving)
18mph = Today. Something is definitely wrong (city driving)

Absolutely nothing wrong. A 2 mile trip will absolutely demolish your fuel economy, especially a big car like the Camry. Your engine is never fully warmed up and operating at peak efficiency.

You know what I got at my last fill up after 3.5 weeks of the same driving habits as you, with A/C use? 13.5 MPG. I almost always get a mix of city and highway but we've been taking my gf's car on the weekends so that last horrible tank was 100% to and from work/school every week. I've never done that before and while slightly surprised, was not all that disappointed with the fuel economy.

I've got the 2.4L 2AZ, my mom has the 3.0L 1MZ. Her car consistently averages 13-16 MPG with mostly city driving. I usually average 18 MPG with mostly city driving. 13.5 MPG with ALL city driving is a bit of a drastic drop but I'm literally at the point where I'm parking just as my engine reaches the middle of my temp gauge.

Like I said, nothing to be concerned about, but you should definitely let your car 'breathe' once every week or two and take it on a longer trip. I can reliably get 30+ MPG all highway in both the I4 and V6, so I know there's nothing wrong with the car. I maintain both myself and keep them in tip top shape.

Enjoy your long drive out to the conference! I love our Camrys. City fuel economy sucks but if I wanted Corolla-like fuel economy, I'd have bought one, and also sacrificed ride comfort and my happiness. I'm very happy driving my Camry, city driving or not

[fenixus]

for comparison my 2002 solara V6 in purely city driving (same 2-mile trip style, never fully warmed up) got me a whopping 16.25MPG




2000 5s-fe did actually 17.04MPG when following the same driving pattern



just checked my ecomodders.com records

[DougB]

There are no codes being thrown and I do not have time to purchase an OBDII off eBay as I have to drive the car to Denver tomorrow afternoon.

This is not typical for this car. Let me just reiterate this fact: THIS IS AN UNUSUAL, AKA NOT NORMAL, CONDITION FOR THIS CAR. I check my fuel economy with every fill-up, so I know exactly what the range should be for my driving conditions. The only times I've had less than 30mpg in the car is when it's been fully loaded with people/gear (so much so that the rear sags), a canoe strapped to the top, and driving into a headwind. In those conditions, I would expect the fuel economy to be between 22-27mpg. I have never gotten anything less than 22mpg.

I typically get over 30mpg no matter what. That's city driving for 2mi back and forth to school. I don't know what/why you guys are used to getting for your particular model, but this condition is not the norm for this car under these conditions.

That being said, I recently changed the timing belt. Perhaps something slipped?

[Solid_Koolaid]

It costs you nothing to check your timing, I mentionned it in my previous post.

Yet if the belt is new and not installed correctly, you'd have got the symptoms since then... it wouldn't have been gradual.

And people are correct, 5SFE fuel economy on such a heavy car can get pretty bad in city driving. 20 mpg and lower ****may**** not be an abnormal condition. But if you say nothing has changed in your driving habits and the weather ain't noticeably colder etc. you may be right about your car having a problem.


EDIT : Especially check the belt tensionner, if it's not been tightened properly, it may throw your timing off gradually.

[fenixus]

so, was the tensioner and spring ever changed or not with that t-belt + wp job?

[fenixus]

just for the record. refilled v6 after same 2-mile short trip driving in city (colder weather now) and got 14.53MPG and there is nothing wrong with it, it's just the driving pattern makes is like that.

... or gas stations switched to some Winter formula of fuels already killing some MPG on our cars in process...