Hi all! My first post here!

My 08 Fit has been getting progressively worse gas mileage since getting the transmission sensor replaced a year ago. What can I do to get it back to where it was before?

Enter the tl;dr section:
In September of last year (2014) my 08 Fit Sport failed a smog check because of a transmission sensor. I was in school in Santa Cruz so I took it to an Aamco there and got it switched fairly cheap. The mech was a young guy who didn't quite seem to know what he was doing but it seemed alright at the time.

I drove it back to the East Bay (about 80 miles) and passed the smog check. But when I got back to my parents' place, I discovered a huge puddle of transmission fluid leaking under the car. My dad said it seemed to be coming from the seams of the transmission. Took it to an Aamco here and I got "oh it was just an old seal, not related to the work the other guy did at all". Hard to believe after 75k miles of no problems.

Since then, I've been getting progressively worse MPG. Before the work was done, I was getting 28-35 MPG, and had never gone under 25 MPG. After, it immediately dropped below 28, only going over 30 once since then. Now, I'm averaging 23 MPG. I haven't changed my driving habits, and I've been driving the same routes. I've gone on long highway trips and still top out at 24 MPG.

The car had about 75k miles on it at the time and I just passed 90k. Did the standard 90k tune up at the dealer and they said everything is fine but it seems very strange that my mileage is progressively getting worse.


Can anyone suggest a solution or something I should try to get my mileage back to where it was? I talk to other fit owners who are getting 30+ regularly and I cry a little inside...


Thanks!

 

have u checked ur transmission fluid level? is it leaking a lot? did ur dealer do a transmission fluid change?

 

After I took it to the second Aamco they fixed the leak and refilled it. The guy said it had leaked enough that I might not have made it back to Santa Cruz... It was stable after that and the dealer changed the fluid with the 90k tune up.

 

Does the engine revs up before shifting gears (let say it used to shift at 3000 rpm, now it does it at 4000 rpm. it will be cool to check torque converter lock-up as well (what are your RPMs when going steady 40 mph at level road.
finally, get AAMCO repair paperwork and past labor description here, I'll try to do an educated guess
Did your dealer perform valve clearance inspection?

 

I don't understand how a transmission switch would cause you to fail a smog test. Especially if a highway trip (which requires little or no shifting) only nets 24 MPG.

Also, there is no 'standard 90K tuneup'. What exactly did the dealer do? Is the engine running OK? (no stutter during accel or idle issues)? <---did it ever have issues in the past?

 

The Auto trans can set a code for a bad switch, the inspectors just see "code" and fail you..
Like they will fail you for an ABS light since it sets a ecu code even though the ABS has NOTHING to do with emissions..

 

Thanks for the replies so far!



It actually used to rev up higher before, and now it doesn't usually get over 4000rpm unless I'm trying to haul ass up a hill.
Haven't had a chance to check RPMs at 40 yet, but I'm going to be driving 160miles roundtrip tomorrow so I will then. I'm also still looking for the AAMCO paperwork; I forgot to input that one into my gas/maintenance app...

They did not perform a valve clearance inspection.

 

I'm just calling it that because that's what the service tech called it. The mileage on the car was 88658, but I was due for an oil change and had had the battery die recently so I just did it then. Here's a list of what they did:
- change oil and oil filter
- replace front wiper inserts
- replace engine air filter
- replace cabin air filter
- flush brake system and replace brake fluid
- complete brake inspection
- rotate tires
- test/inspect battery
- top off underhood fluids
- replace spark plugs (non-platinum)

They found the battery to be underperforming so I got it replaced at that time.

 

I found the AAMCO paperwork, as well as the smog test paperwork!


Smog test: Failed because "P0847 - Transmission Fluid Pressure Sensor/Switch "B" Circuit Low"

First trip to AAMCO: replaced 3rd Clutch Pressure Switch. They found no problems with the transmission or fluid levels.
- Mileage here was 79374

Second trip to AAMCO (after passing smog, and then finding the leak): inspection revealed that transmission fluid level is low and the condition is normal. Transmission leaking from seal from line. A computer scan revealed the following codes: none. Services: replace seal; added 2qt of Honda Fluid.
- Mileage here was 79510

 

Well as far as for AAMCO they performed TSB work addressing the 3rd gear pressure switch failure and reused the gasket or crushed the new too much. If the mechanic used the pliers instead of 22 mm deep socket for installation he may damage a switch as well (saw this when changed the engine oil pressure switch on older Toyota which is basically same design. In theory, "weak" engine causes late up-shifts (4k rpm instead of 3k rpm let say)
So more thinking is required. If this switch was screwed up ort incorrect type it should affect shift pressure on 4th and 5 th gears. Higher fuel usage typically corresponds to engine lugging (driving in low rpm at high gear)

 

Ok, so is this just something I'd have to take into a transmission place and have them tinker with? I don't really want to spend the money but if it saves me in gas and future work, it'd be worth it.

Also, I checked my RPMs on my mini road trip the other day. I'm sitting right about 1600 RPMs going 40MPH.

 

I'm sitting right about 1600 RPMs going 40MPH. Mine does the same, so the top gear is engaged and torque converter is working (engaged). I honestly don't think the problem is in the transmission but if come air intake components were removed (this is NOT necessary for 3 rd gear pressure switch change but who knows), it is possible they were not put back correctly.

 

"replace spark plugs (non-platinum)" WTH??? Didn't they put what the owner manual specified??

 

So doctor j, what would you recommend I do? Unfortunately I'm not very technically inclined but if there's something simple to check I can enlist my dad to help.

As for the spark plugs, I don't know. That's just what was written on the work receipt that they gave me. For what it's worth, I'm going back to the dealer tomorrow because I've been having that 'stalls when starting up' problem since that tune up and they're dodging my calls...

 

This makes situation a little easier. Stalling after start, especially when going into the gear is often causes by tight exhaust valves. If engine starts and stalls in park the EGR valve can be leaking (but this is not common issue so far) The spark plugs have to be pulled out and their marking should be checked against recommended in manual.

 

BTW I NEVER had my MPG above 30 (averaging 28-30) I am using cheapest 87 gas with ethanol that's why

 

If Napa's catalog says these random-ass plugs are okay, then they're okay. I'm not advocating that, but if you go to a random-ass shop then that's what you get.

If you want OE spec parts and work you go to a dealer or to a shop that will use (and charge for) OE. If you pick your shop on price and convenience, you're eating off the McDonald's dollar menu of parts and service, so to speak: technically it's correct, but...

I use 87 octane with ethanol as well. Never gotten below 37 for a tank except for the one time my wife drove it for half a tank in the winter.

 

I took it in yesterday and they told me its running lean and recommended the valve clearance adjustment and throttle body intake clearout. Hopefully that solves my stalling issues (it seems like it helped everyone else out in the stall thread) and maybe it'll help me tick up the MPG?

For what it's worth, I always used 87 gas and still averaged 29-30 MPG before the whole transmission thing.

 

What evidence did they find that makes them think it's running lean?