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Discussion Starter #1
ive got a 2000 gt convertible automatic

i was having the a problem with bad gas mileage, an average of 10 mpg and this is what i did. new gas filter new air filter i went with k&n, had my injectors cleaned, and new plugs. i cleaned the throttle body and even the egr. and nothing. it turned out that my thermostat was bad. i looked it up in the haynes manual and it quotes.
" Do not drive the vehicle without a thermostat! The computer may stay in open loop and emissions and fuel economy will suffer."

So i tried it, it must have worked because as soon as i replaced it and started the car it started misfiring minutes later, i was like what is going on now! i was about to loose my mind. lol. and like 10 min later the car was running like new.I take it that the computer resets itself, i had no idea. so i filled up today and reset the trip. ive run like 20 miles and the needle hasnt moved at all.

also other possible malfunctions: dirty or clogged air filter, incorrect timing (5.0 l engine), incorrect idle speed, low preasure tire or incorrect tire size, binding brakes, fuel leakage, dirty or clogged injectors, fuel injection or engine control systems malfunction, thermostat stuck or open or not installed, improperly operating transmision, dirty or clogged fuel filter, and bad spark plugs.

hope this helps
 

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That is good info to know. 20 MPG is about right and I was worried when you only were getting 10 . I am also going to pick up a Haynes manual to have around the house.
 

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The manuals are not bad to have I got one when I bought my 98 had to do an intake swap was iffy about it with all the hoses and wires considering it was my first work on a FI car but I read the part in the manual looked at the pics and went at it everything was smooth took my time and it worked out just fine. They don't show or tell you everything that would make it perfect but if you got the mechanics knowledge then you should be fine. I get about 17.5 mpg in the city and around 27 on the interstate but again gears has a little role in that I have 2.73 gears so I can cruise at about 2300 rpm's at 100 mph and it does not seem you are going that fast either lol I got a $500 ticket that says so.
 

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yes the book will save you lots of time money and unanswered questions i buy a book for each car i have. im a do it yourselfer. now as far as the books i would recomend the childers over the haynes i think it a bit more detailed. autozone markets the haynes and orileys markets the childers. and i picked this one up because i couldnt find the childers at the time but it works, and never in my crazy mind would i have ever thought that my thermostat was the solution to my problem.
 

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Yes I agree with you on the chiltons manuals.
 

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I am glad to see a consensus about the Chilton manual. My need is pretty simple as I plan to dress up the underhood with a CAI, Yellow Optima Battery (Car is Zinc Yellow) and swap hoses with Ford Blue replacements of tube wrap. Don't want to be in a fog if I accidently lose track of where something should go.
 

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CAI is a simple bolt on you don't need instructions for it really it took me 20-30 mins to take off my factory assembly and install my BBK CAI.
 

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Discussion Starter #9
ive got a 2000 gt convertible automatic

i was having the a problem with bad gas mileage, an average of 10 mpg and this is what i did. new gas filter new air filter i went with k&n, had my injectors cleaned, and new plugs. i cleaned the throttle body and even the egr. i sprayed the maf sensor down with carb cleaner and nothing. it turned out that my thermostat was bad. i looked it up in the haynes manual and it quotes.
" Do not drive the vehicle without a thermostat! The computer may stay in open loop and emissions and fuel economy will suffer."

So i tried it, it must have worked because as soon as i replaced it and started the car it started misfiring minutes later, i was like what is going on now! i was about to loose my mind. lol. and like 10 min later the car was running like new.I take it that the computer resets itself, i had no idea. so i filled up today and reset the trip. ive run like 20 miles and the needle hasnt moved at all.

also other possible malfunctions: dirty or clogged air filter, incorrect timing (5.0 l engine), incorrect idle speed, low preasure tire or incorrect tire size, binding brakes, fuel leakage, dirty or clogged injectors, fuel injection or engine control systems malfunction, thermostat stuck or open or not installed, improperly operating transmision, dirty or clogged fuel filter, and bad spark plugs.

hope this helps
allright now its been a couple of days now since ive filled up the tank and have driven 66 miles and only waisted 1/4 tank all city miles and i havent been nice to the car. so on average im getting 17 city miles. daang that makes me happy!!!! as i used to get like 30 to 35 miles per 1/4 tank. im sure everything i did was good, but that darn thermostat was the thing that was killing my walet.
 
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