GTPONYPWR

Hey, guys, I own a 2004 Mustang GT completely stock. Lately, I’ve noticed that my car consumes gas more than usual. This seemed to be happening gradually but I’m starting to notice it more with the price of gas. My car is well taken care of, K & N air filter and regular maintenance, synthetic oil, injector cleaner etc… it’s my daily driver and it’s driven in the most fuel efficient way possible (some days I like to have fun though!). Even though, it’s not a fuel friendly vehicle, the gas consumption is getting way out of hand (I’m getting around 150km less to the tank highway/city conditions) and there doesn’t seem to be any apparent fuel leaks. It also hesitates to start when it’s hot (turns and cranks over but struggles to start) and idles rough; the stock plugs were professionally replaced with iridium plugs trying to resolve this problem. None of the mechanics can diagnosed the problem and the new plugs didn’t help. Then my starter fried at the same time that my belt tensioner went so replaced the starter, the pulleys, tensioner and belt. I need some help, any ideas or anyone had the same problems? Could the hesitation to start be fuel related and affect my gas consumption?

Stang6589

iTrader: (1)

I am thinking a vaccum leak or O2 sensers. Maybe the car does not like those plugs, try putting in stock ford plugs.

GTPONYPWR

I thought it could be the new plugs, though would better performing spark plugs than the stock ones do the reverse effect and give me worst gas mileage ? Could of the plug gap be set wrong ?
Thanks for your help. Don't mean to be asking a million questions but no repair shop has been able to help me so far.

Stang Illusions 5.0L

iTrader: (10)

Your first problem is that K&N Air filter. THEY ARE JUNK! Swap it out with a AMSOil Air filter.

http://www.amsoil.com/

Second of all, DUE TO THAT POS K&N air filter and the OIL on the useless things, there is probly OIL on your MAF (Mass Air Flow) Remove your MAF and spray the hell out of it with a GOOD brake clean, and be sure not to touch the diodes or could result in damage.

These problems you are describing to us all result in a dirty MAF, like I said due to OIL from your filter.
Dirty MAF's will cause decrease in HP gains, lower fuel mileage, poor idles, poor acceleration "Hesitation", Etc.....

Cleaning the MAF is possibly the cheapest thing you could ever do. I clean mine 1-2 times a summer, depending on how much I drive the car.

Note: If you don't have a good brake clean like "Red Stallion" be sure to use a electrical spray to remove any residue.

Hope this helps good luck.

GTPONYPWR

Thank you, I wouldn't of thought it could be the oil from the K & N air filter but I'll have a look at it, clean the MAF and go from there. It's great advice. I've been running out of ideas and since no trouble codes ever show up on diagnostic I always get "everything is fine" from the mechanics. Great help. thanks !

Marcstang

FYI. You'll need a T-20 Tamper proof Torx bit to remoce the MAD. NAPA, $7.12.