Hey Everyone,

So I just bought a 2009 Mustang GT (29,000 miles) about 30 days ago. Very clean car. I figured even though I bought it from a dealership (they claim to have changed all the fluids) that I would have the basics done by an independent mechanic. I personally changed the air filter, cabin filter, cleaned the throttle body, and cleaned the MAF sensor. In addition, I had the oil, oil filter, and fuel filter changed by a mechanic.

The items I changed was done two weeks ago and the mechanic items were done four days ago. On my drive to work today the check engine light came on. So I went over to AutoZone and they checked the codes. It is throwing P0171 and P0174 which according to the research I have done is issues with the air/fuel ratio.

What I am confused about is so far what I am reading is these codes are usually caused by items people don't address the items I have done above; like clean the MAF sensor.

The only things I have not checked are:
*oil dipstick is seated properly
*gas cap is on tight
*re-clean MAF; when I cleaned it I barely let it dry before putting it back in....maybe that did something?

Can anyone provide some tips on getting this resolved. As far as I know, the engine and car are 100% stock.

 

I just went out at my lunch hour to look at the engine. I noticed the air inlet part that connects to the air box is crooked by maybe 1-2 cm? Then I also noticed the oil dipstick was not put on and sticking up. So I put it back down. Maybe that was causing the issue? The light is still on but I figure I need to disconnect the battery for it to reset which I can't do at work...

 

those are lean codes, could be a MAF problem, a vacuum leak, or a leaking air inlet after the MAF

 

Fluids are easy to check. Just look at their color.

PS Fluid - Basically tranny fluid. It should be bright red with no dirt in it since it was replaced.

Oil - Clean light to medium brown not dark brown or black. Should just smell like oil, no fuel or burnt odor

coolant - Bright yellow or red depending on the year and clear..no clouding or floating stuff. The tank should be free of any crud.

brake fluid - very light tan almost clear. Clean fluid on these cars looks almost invisible when viewing the Master cylinder from outside the reservoir. In other words if you can easily see the fluid in the tank from outside the reservoir (darker) then the fluid is not new.

You problem is most likely what you already spotted, the intake hose from the air cleaner to the intake itself. What do you mean by misaligned but 1-2cm...pic?

 

You may have messed up the sensor when you cleaned it

 

Well when I got home yesterday I basically took everything apart from the throttle body to the air intake box - even took out the air filter. Then I put everything back together step by step making sure everything was securely attached and tightened down. I did notice the rubber o ring for the throttle body was sticking out on one end so I pushed it back into the groove. Bolted everything back up. I re-cleaned the MAF sensor and let it properly dry for about 5 minutes.

Two weeks ago when I bolted my throttle body back together I tightened the bottom bolts then the top bolts. I was being lazy since for some reason the top bolts are a different size then the bottom ones. This time I tightened them in a cross pattern.

Finally, I made sure the oil dipstick was secure since at lunch it was sticking out about 1-2 inches. Reconnected the battery and started the car up. No more check engine light!

Since yesterday I have driven about 40 miles and there is no light so I am going to assume it’s fixed. I am still not sure what caused it but its fixed!

 

I've had the same code on numerous Fords off and on for years when they are doing winter blend gas here in CO. I've gotten to the point where I clear it and move on.

 

Glad to hear it is fixed. As for cleaning the MAF, you never want to run power through it when it is wet. It will fry itself. The little wires inside there get really really hot really quickly and any moisture on them can break them. So next time let the MAF completely dry before re-installing it.

 

So there is no way other than a code checker to determine the codes?

I have had numerous cars that gave code numbers simply by turning the key on-off several times.

 

the old OBD1 cars (up to 1996) would have flash codes , but since OBD2 came to be the codes are alpha numeric and are 5 digits long, so no more flash codes , u need a scantool