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Discussion Starter #1
I'm getting 170 to 190 miles per tank, no CEL. Runs strong..just cant seem to figure it out. 01 is300 automatic with 133,000 miles. Timing belt done recently along with new water pump, new head gasket along with resurfaced head..all other seals were done at this time also. It's not leaking oil or low on coolant cuz I've been checking it every few days. So confused, also has new spark plugs and wires. Any idea what to check next? Just replaced vvt solenoid and pcv valve also
 

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Have you checked the injectors? Seems like the next logical step, when I replaced mine, the o-ring seals have to seat just right for no leaks
 

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Discussion Starter #3
I haven't checked the injectors yet I'll have to when I get some free time to work on it , was thinking about seafoaming it through the pcv hose to see if the gas mileage improves at all. Maybe some in the gas tank also..
 

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Discussion Starter #5
Per gallon I'm getting about 10.5 to 11 miles or so. It has been like this since I've got it 2 months ago. It runs solid as a rock and hasn't given me any issues besides this gas mileage. I'm in California and only use Chevron 91 premium gasoline
 

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I average 20 to 24 mpg in my '05 5 spd car. It depends a lot on how I drive it.

Check your air filter and while its apart, clean the MAF sensor with the correct cleaner.
 

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Per gallon I'm getting about 10.5 to 11 miles or so. It has been like this since I've got it 2 months ago. It runs solid as a rock and hasn't given me any issues besides this gas mileage. I'm in California and only use Chevron 91 premium gasoline
It may be the way you are driving. The few I have dealt with. Only get that bad when I real pound on the accelerator.
 

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Discussion Starter #8
I cleaned the MAF but I used electronic cleaner and also cleaned the K&N air filter with k&n cleaner and lightly reoiled it after . I will fill up and try to drive it as light as possible as I do have a heavy foot and see what the difference might be there.
 

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Discussion Starter #10
No fluids leaking or dripping at all I've been looking daily. Once in a while I smell gas but it's usually at 5 am when I warm it up for work and its 47 degrees outside. The inside of muffler tip is black but nothing out of the ordinary looking for the year of the car
 

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No fluids leaking or dripping at all I've been looking daily. Once in a while I smell gas but it's usually at 5 am when I warm it up for work and its 47 degrees outside. The inside of muffler tip is black but nothing out of the ordinary looking for the year of the car
So if you pull the spark plugs, you can look at the tips and if they're gunked with carbon, odds are you're running extremely rich, which could be tied to a bad o2 sensor. If it's not the injectors I mentioned earlier
 

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if it was running extremely rich, that's why I'd look for the black buildup above the exhaust, but it's not there. It would also make CELs eventually, which he doesn't have. If it was running extremely rich, wouldn't it be obvious?
I suppose it would, my CEL bulb was actually removed before I bought my car so there's an chance he's in the same position. I just can't imagine getting half the economy without the ECU seeing something wrong.
 

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Was the cam belt and other work done before you got it?

Could also be possibly the belt is out a tooth, it may or may not run right with a tooth out depending on how its out, but may not be making power like it should and so you are gassing it more than it should be. If you hadnt driven it before or haven't driven another IS then you may not have noticed.

I would pull the battery for a minute or so to reset the ECU and then give it a try. It might set everything right after cleaning the MAF and other work, or it might throw a CEL if something is wrong and it finally tell you whats going on. I would also get the CEL's read properly, dont wait for the light as it often only lights up on critical items, but might overlook something else.
 

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Discussion Starter #16
Ok so it finally threw codes today. P0174 p0171 p0440. I guess start with replacing the MAF? I see fuel injector seal on the p0714 as a option after MAF which one of you guys mentioned before...the p0171 I'm not sure cuz it's got a list of things, but MAF being first
 

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Ok so it finally threw codes today. P0174 p0171 p0440. I guess start with replacing the MAF? I see fuel injector seal on the p0714 as a option after MAF which one of you guys mentioned before...the p0171 I'm not sure cuz it's got a list of things, but MAF being first
171 & 174 means you have a vacuum leak. Check your hoses. The 440 is evap leak and will not effect running. It may even be caused by the main vacuum leak.
 

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Discussion Starter #18
I checked hoses this morning and none are cracked. I hit most of them with carb cleaner and no change in idle. Is it possible it threw these codes from when i seafoamed through the pcv vacuum line into the intake ? It seems to be lagging now forsure tho
 

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I checked hoses this morning and none are cracked. I hit most of them with carb cleaner and no change in idle. Is it possible it threw these codes from when i seafoamed through the pcv vacuum line into the intake ? It seems to be lagging now forsure tho
If that is the case it should cycle out. Try clearing and doing a drive cycle. If they come back. You still have a leak.
 

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