1998 4.6 concerns

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thewishkah

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1997 4.6 concerns

I have a 1997 exp with the 4.6 liter engnie and I know these trucks aren't great on gas and I know they get even worse once you throw a set of big tires one them. I have BFGoodrich 315/70 r17's on my truck currently and I am averaging about 8.5-9mpg high way which seems a little low even for those tires.

Now my concerns besides the gas mileage are when accelerating heavily or on an incline the exhaust sound like the truck is missing, like it sounds like it's sputtering. I can still accelerate but it doesn't sound right. There is no check engine light on nor has there been since I bought the truck. (the light does function) The other concern is after I have idled for a period of time (10-15 min or longer) when I hit the gas I get some smoke from the exhaust. Not a lot or for any amount of time just on the initial press of the gas when I go to start driving. I have checked my pcv valve and the hose going to it and they are both good. (shake pcv and it rattles and took the hose off and blew through it to make sure it wasnt clogged).

One last thing that may be tied into it all is sometimes the truck will start to idle rough but never throws a code. I have a decent actron scanner that can read the live data on screen if there is anything I can check that would help diagnose these issues. My initial thoughts were to change the spark plugs and wires (not COP) has the quad coils on each bank at the front of the motor. Then I got to thinking it could be the catalyic converts. Any input on these issues would be greatly appreciated. Thanks and have a great day!
 
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IMINYOURCHAIR

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as far as the smoke after idle, what oil are you using? My 4.6 does the same thing from time to time but she has 287k miles.

as far as fuel mileage goes what rear end gearing do you have? My expy has stock tire size with the 3.31 getting 16mpg average to/from work. I got 20 mpg on the highway to/from florida a couple of months ago.
 

Bedrck47

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I would suggest that you pull the throttle body and clean the exhaust ports that go thru the TB the 4.6 has two ports that tend to get carbon fouled.
There is a very good video on you-tube on cleaning the TB
 
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thewishkah

thewishkah

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Thanks for the input. It is running 5w30, i think quakerstate? I brought it to the quick change place which uses quakerstate I believe. I do not know off hand which gears are in there but im certain they are stock, I will have to check the vin later to see for sure. It currently has 119,000 miles. Not sure if the plugs or coils have ever been changed or not. I do know that the wires and coils are motorcraft that are on there now and look almost brand new. (NOT COP)

The previous owner had it for 4 years and barely put 15k miles on it(going by the title date and mileage from when he bought it to when I bought it). Since I got the truck I did front and rear brakes, pads, rotors, and parking brake shoes.

I also was having an issue with a sticky IAC so I took it off cleaned it out, cleaned the tb intake, cleaned the mas air flow sensor, changed the air filter, changed the fuel filter which all made the truck run better (it had stalled while in reverse once) also the IAC does not stick anymore. I guess I will start with the plugs, wires and the tb exhaust ports next, then from there if the issue presists I'll move on to the coils.
 

Bedrck47

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go to
ford etis
enter your vin number and you will see what all was on the expy when built it will also give you the gear ratio
 

FordandPolaris

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There is an axle code on the door placard (drivers door) that would tell you the axle ratio. H6 is 3.73 LSD and H9 is 3.55 LSD. If it's anything else google will be able to tell you


Sent from the Pocket Computer
 
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thewishkah

thewishkah

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I haven't gotten to change any parts yet, but I took the truck from NYC to Myrtle Beach SC last week, 1600 miles or so round trip with in town driving while down there. I averaged 11.5 mpg the whole trip based on miles traveled divided by gallons used to fill up each time. I know its not 100% accurate but it is close enough. I plan to tackle the plugs and TB ports this Thursday. I also have forgotten to check which gears I have lol.
 

Madmaxwell87

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Are you adding roughly 15% of the mileage back on to what the odometer says to account for the larger than stock tires making it seem like you are travelling less distance? Most of these trucks came stock with 30-31's so having 35's changes that.

While you're looking at the door sticker to see your axle code it should show the stock tire size. Plug that size into a tire size calculator and the new tires and that will tell you the % difference between the two. Then you take that percent of your final mileage and add it back on to get the true distance you traveled.
 
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thewishkah

thewishkah

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Sadly I have. lol From what I've got for every 60 miles on the odometer I travel about 66-67 miles it seems. On the trip I would fill up when it got to half a tank which was always close to 150mi on the odometer which I estimated to be about 167 miles or so.167 divided by 15(half tank) =11.1 mpg but I am rounding up to 11.5mpg to make myself happy lol.

Later today I plan to check out the TB ports and clean them out. With the removal of the TB would changing the plugs be any easier? I haven't really checked how bad it will be to get at the plugs in this truck. I know on my Grand Marquis (4.6 also) they are pretty easy as they just drop straight down but I dont know how much of a PITA they will be to get at in the truck. Thanks for any input.
 

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