MPG Loss...

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Dark_Majesty_06

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I have done a search.. but only turned up old post.. nothing that helped... I was getting great mpg about 2 weeks ago.. even in the stop and go of city and stuff.. I was getting 20.2.. after I changed my plugs and put a new paper air filter in.. i'm only getting.. ONLY ... 17 mpg.. I was doing really good for awhile.. on the highway.. used to.. I would get mid 20's.. even driving home.. cuz its all straight and flat.. I was getting low 20's.. what could cause this..? I have a new fuel filter.. but could my o2 sensors be bad.. or what? I'm not getting a sulfer smell or anything... what could cause a horrible drop like this.. I understand.. when i gun it.. it will drop.. but i'm hardly gunning it anymore.. afraid of loosing more mpg... and hurting my tranny...
 
How many miles are on the car? Have you ever replaced the O2s before? How is it idling?
 
Oh man brother.. its at 203k and climbing rapidly because I drive alot.. and oh man.. have I tried... 2 weeks owning the car.. 2 cans of seafoam.. tank and crank.. multiple fuel cleaners.. just to make sure... I'm assuming the o2's have never been changed in thier life.. so that could be the problem.. idle.. good idle.. only 2 times.. in the whole ownership of my car.. has it idled up.. to 1k.. down to 5 hundred and died.. only 2 times.. it does hesitate on take off sometimes.. only when its completely cold.. IAC or TPS?
 
gap is set to .048.. exept for one.. which is the front passanger side.. I couldnt get it out.. I forgot to gap.. so I went back and pulled all of them.. by the time I got to the last one.. I was mad.. and it wasn't commin out.. so I just left it.. but the pre gap setting is .045.. does it make a diffrence that I went to .048 or is it because that one isn't gapped right.

Yes.. Premium fuel!!
 
Don't worry about the miles except that the miles may mean it's time to replace parts like the 02s. Also don't run anymore fuel system cleaners... Looks like You've done that enough.
 
Spark plugs are usually not "pre-gapped". When I buy them they are gapped all over the place....

But which park plug you get?
 
I got the Ap24.. I wanted app724.. but at the moment.. money was tight.. still is.. well true.. some are pre gaped.. others are just poohed on... no more fuel cleaners.. I'm afraid anymore.. and i'm gunna clean my car to death.. lol.

No fuel pump change.. fuel filter is sitting around waiting on a nice sunny day after work when my house isn't flooded... I'm hoping once I get a radio.. and front bags... then i'll get a walbro.. or something along those lines...
 
I've only used motorcraft copper spark plugs and they work great. My guy got them for me for a little over a buck a piece.
 
Ya, those Motocraft AutoLite 764 are pretty much the best you can get, and the cheapest. Anything else will diminish performance and economy.

5th grade physics, copper is the best high heat conductor. Silver or gold would be great but never hold up. Platinum, iridium, etc.. those all conduct less.
 
Yeah.. I'm going to pull'em out today.. and make sure thier all gapped correctly.. Now since I don't have the app series.. do they still need to be gapped at .048? Also.. I know this is totally off my own subject.. but do I really have to have a special tool to remove my fuel filter?
 
Dark_Majesty_06 said:
Also.. I know this is totally off my own subject.. but do I really have to have a special tool to remove my fuel filter?
Click to expand...

Yes you will need the tool, but they are not expensive should be less than $20 at any auto parts store. Fuel filter is easy but sometimes they like to be a bit of a PITA, at least the top fitting.
 
dag nab it.. I always have to wait for this crud.. lol.. okay.. well then fuel filter will be this weekend.. after that.. I guess next big project is fuel pump..
 
Ah the fuel pump. Make sure you have the tank almost empty to make it easier.

Also it is not a real PITA but at times can be. JD Auto Parts is a great place for a good 255 pump...
 
what i see a lot of the times is when you replace plugs that have been in the engine for a long time, the cylinders carbon track the the spark of the old plug. when the new one is installed, it will fire completely different. it usually take a couple of tanks of gas to get a new carbon track in the cylinders. don't worry. you should notice the car doesnt start quite as easy as it did with the old plugs unless they were misfiring. Just FYI, give it a few tanks.
 
Okay thanks a whole lot cobrastar! I sure appreciate that information.. I will give it a few tanks and see if everything gets back to normal!!
 
98CobraStarLSC said:
what i see a lot of the times is when you replace plugs that have been in the engine for a long time, the cylinders carbon track the the spark of the old plug. when the new one is installed, it will fire completely different. it usually take a couple of tanks of gas to get a new carbon track in the cylinders. don't worry. you should notice the car doesnt start quite as easy as it did with the old plugs unless they were misfiring. Just FYI, give it a few tanks.
Click to expand...

I can say I have never heard of that in a modern engine. Whenever I replaced plugs that were bad the vehicle immediately ran smoother.

Can you imagine all the people that would be taking cars back to dealers or tune-up shops if this was at all common?
 
Yea I've never had that issue and I've change plugs for a handful of people with these cars.
 
4x4 mags have done several articles about how they lost mpg after a routine tune up. If you don't neglect it in the first place you'll be fine. The copper plugs are the best you can get, 5th grade physics and all. You can get a cheap fuel line remover made of plastic for about 5 bucks. They work about 3 or 4 times before they are shot. Run a real intake fuel system cleaner before changing the plugs, not seafoam. Then see how she runs.
 
Ya know, I wonder is something broke after moving all those parts around to get to the plug covers.

A vacuum leak could also cause these issues. Everything from a cracked line to a bad seal of the intake tube to the throttle body.
 
unity said:
Ya know, I wonder is something broke after moving all those parts around to get to the plug covers.

A vacuum leak could also cause these issues. Everything from a cracked line to a bad seal of the intake tube to the throttle body.
Click to expand...


Vacuum good thought. I just changed cracked vacuum lines my daughters car.
 
If its not stinking raining today after work.. I'll check my Air Intake to TB seal.. and i'll check all the surrounding vac lines.. I did a reset yesterday on my MPG.. and it was being stupid.. it was registering like.. 29.6... I don't think my car is getting that.. well.. it went down to 18-19 after I hit 125... Totally off topic here.. sorry.. but our cars aren't meant for high speed are they? My car felt like I was floating.. I was all over the road...
 
Dark_Majesty_06 said:
If its not stinking raining today after work.. I'll check my Air Intake to TB seal.. and i'll check all the surrounding vac lines.. I did a reset yesterday on my MPG.. and it was being stupid.. it was registering like.. 29.6... I don't think my car is getting that.. well.. it went down to 18-19 after I hit 125... Totally off topic here.. sorry.. but our cars aren't meant for high speed are they? My car felt like I was floating.. I was all over the road...
Click to expand...

In my eco-tune from Torrie I get 30 to 32 MPG. In performance at 65 I get 27 or 28 MPG. 29.6 is possible thanks to the locking TC the trans has.

As for floating, it is air-ride which helps a lot. Do you have it lowered? Is the air-ride working correctly?
 
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