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06 Maxx SS MPG

4671 Views 28 Replies 8 Participants Last post by  Alan06
My 2006 Malibu Maxx SS (3.9L V6) is averaging 13.67 mpg. My last fill up was 11.6 mpg!
I purchased this vehicle a month ago and track my mileage on every fill up. This is not the information coming from the computer, these are my calculations based on miles driven between fill ups.
I replaced the EVAP purge valve and got a new gas cap after a code. The CEL hasn't gone off since.

Any ideas on why the vehicle is getting HORRIBLE gas mileage?
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There are tons of things that can affect MPG. The state of maintenance on the engine in general, spark plugs, O2 sensors, catalytic converters, MAF sensor, clogged intake or throttle body. What possibilities have you eliminated?
I haven't elimiinated any of the above. I'm a bit of a newb, but I'm very capable of moderate repairs/maintenance.
What would you start with? At 96k miles I should start with plugs? If I remove the O2 sensors, can I visually inspect them for wear? What about the fuel injectors?
1. Absolutely check and replace the plugs with OEM spec, you're due.
2. Open and inspect the air intake box and filter. Remove the filter and look for clogs, install new OEM paper filter if necessary.
3. Pull the MAF sensor and visually inspect the filament for crud (do NOT touch the filament, buy a dedicated touchless MAF cleaner spray).
3. Open and inspect the throttle body. Spray a rag with throttle body cleaner and thoroughly clean it out if dirty.
4. Add a bottle of techron injector cleaner to a half tank of gas and drive the car aggressively to clean out ports and injectors.

Techron injector cleaner:

CRC MAF Cleaner

CRC Throttle Body Cleaner
I just replaced plugs and wires. Intake and filter were cleaned/replaced with oil change after purchase (1 month ago). I regularly blow and vac the filter and vac out the intake box. MAF visually appears clean. I did a fuel induction and throttle bottle cleaning. I'll throw a bottle of injector cleaner in today. I also did this immediately after purchase.
Fingers crossed.
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At 96k your due for plugs. Change the O2 sensors also, use only AC plugs and sensors, the upstream sensors that are closest to the engine as they control fuel mixture. There is no looking at the sensors to see how they are like a spark plug. O2 sensors get lazy / slow responding as the miles go on.
I've gotten back 2-3 mpg on putting in fresh O2 sensors.
Clean MAF
We all have been down this road and this is what has worked for us.
Is there any difference between O2 sensors? I'm seeing a Bosch @ $140 and a Walker @ $125. Does the extra $15 make a difference?
Replaced plugs and wires. Had throttle body cleaned. Put Techron fuel injector cleaner into tank. Just came inside from replacing 02 sensor (upstream/ACDelco). Fingers crossed.
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So ... I'm still sitting at 13 mpg UGH! When I run the car there is a kind of exhaust/oil smell coming in from the vents (noticed more now that I'm running the heater). I got a FIXD OBD2 device and it indicates potential 02 sensor issues and potential EVAP system. Again, I've replaced EVAP solenoid/purge valve, replaced upstream 02 sensor, replaced sparks/plugs and had the throttle body cleaned. Also, I've run a bottle of Techron fuel injector cleaner through. Any suggestions for next steps?
What are you basing your fuel economy estimates on? If you're using the gauge cluster average readout, have you reset it since doing all the work?
NOT using the gauge cluster. I track my mileage and calculate mpg everytime I fuel up.
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What are "potential" ussues withe EVAP and O2 sensors? I suggest you take care of the EVAP problems first.
I'm not sure at this point. I have replaced the EVAP solenoid/valve (at manifold) and upstream 02 sensor.
Can anyone help me with the location of the Vapor Canister on a 2006 Maxx SS (3.9L)?
I've looked around the rear wheel wells and don't see anything that resembles it. I thought I'd seen somewhere else that it is tucked above the gas tank and that the tank needs to be lowered to get to it? Does anyone know if this is the case? If so, is it a DIY project or do I need to fork out the labor $$?
Fuel economy is suffering and I've pretty much gone down the checklist and replaced O2 sensors, sparks and plugs, cleaned throttle body and MAF, cleaned fuel injectors ...
Cannister is in the bottom right of both of these photos, passenger side, forward end of tank. Photos are from a 2006 LS, not an SS.
Thank you! Do you know if they can be gotten to w/o lowering the tank?
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