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1990 f-150

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87jd318
Join Date: Apr 2006
Posts: 11 Northern California
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2006-04-04          127172

Hey guys i have a f-150 with a fuel injected 6cyl and a 5sp manual trans. The truck is excellent cond and runs great. I do however have a issue with fuel milege. I'm getting + or - 12mpg. I have a KN air filter otherwise all is stock. Recent tune-up all seems to be good.What should i expect to get for milege? I've owned the truck for about 6mo. and i bought it off original owner,my good friend. Also one other slight problem is sometimes when i start out from a stop i get some hesitation. This is a intermittent problem. Any ideas? Thank you

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1990 f-150

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wingwiper
Join Date: Jun 2004
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2006-04-04          127174

Is it 4X4 or 2wd? is the rear axle ratio 3.55 or 3.92?
Is it fuel injected as in Sequential Multi-point or throttle body? Size of tires? Reg cab or Club? 6 1/2 ft box or 8ft? this will all have an effect on your MPG as well as are you driving flat highways or hills and mountains. Here in Vt the 4.7L * cylinder will give better MPG becasue with the mountains the 6 cylinder labors more.
For maximizing yoour MPG I would suggest using NGK V-Notch spark plugs.You will witness a lot of difference. Unlike the Splitfire Plug the NGK V-Notch offers twice the amount of spark whereas the Splitfire splits the same amount of spark in half. More spark better combustion and more complete. When I switched years ago, I now downshift one less gear climbing the mtn home and my Throttle body, 318, reg cab, long box, with LT245 70 15 tires and 4x4 and 3.55 rear axle ratio gets 15 mpg regardless.
I have sold 4.7L Pick ups that have gotten anywhere from 13mpg to 20mpg, alot is also in driving habits. Understand that your truck weighs meore than your car and when you step on the gas you are putting that weight into motion and that requires energy which requires fuel. If you are light on the pedal and keep the RPMs down and the MPH up, you will get the best Gas mileage that you can. If you drive your truck like a car, you will witness terrible gas mileage.
Sorry for the long reply but there really is NO real answer to your question, too many factors.
....

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1990 f-150

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87jd318
Join Date: Apr 2006
Posts: 11 Northern California
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2006-04-04          127178

The truckis a supercab short box. I belive it has a 355 rear end.Multiport injection. I drive on mostly flat to somewhat hilly. Stock rims with 31-10.50-15. Any thoughts on the hesitation question? ....

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1990 f-150

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87jd318
Join Date: Apr 2006
Posts: 11 Northern California
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2006-04-04          127180

I'm sorry its also a 4x4. ....

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1990 f-150

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wingwiper
Join Date: Jun 2004
Posts: 676
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2006-04-04          127181

Clogged Fuel Filter, corroded fuel line, clogged Injectors. You can add injector cleaner, then run only High Test for a tank or two, add Dry Gas and change your filters. Try the NGK Plugs and have fun. I would guess on flat ground, no extra cargo or gear you could expect maybe 18 or 19 and maybe even 20 with 2wd and if 4X4 then you can expect 14 to 17. Your BIG tires are putting alot of resistance to the motor and drive train, so that may have a Big affect on your MPG, you have a lot of rubber on the road and a lot of torque to turn them. Your 3.55 may be a weak ratio for what you are using for tires and may destroy your MPG. I don't have a lot of experience with the BIG tires. I do know that Gas mileage is decreased big time with them... ....

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1990 f-150

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wingwiper
Join Date: Jun 2004
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2006-04-04          127182

Your axle ratio will be on a label either under the hood or in the glove box. ....

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1990 f-150

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87jd318
Join Date: Apr 2006
Posts: 11 Northern California
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2006-04-04          127183

Thanks for your time on this issue.I'll check my rear end ratio and try your suggested fuel additives and filter replacement. ....

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1990 f-150

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oneace
Join Date: Mar 2004
Posts: 1490 south central pa
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2006-04-04          127199

Make sure your hubs are unlocked. With my old 89 4.9L 5spd I would lose 5mpg if I left the hubs locked in. Hesitation could be that it needs a tune up or may be the throttle position sensor. ....

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1990 f-150

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SG8NUC
Join Date: Jan 2006
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2006-04-04          127201

oneace
Is the 4.9L the same inline 6cl that ford has always made. ....

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1990 f-150

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87jd318
Join Date: Apr 2006
Posts: 11 Northern California
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2006-04-04          127203

Thanks for your reply, the hubs are unlocked and i'll check into sensor. ....

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1990 f-150

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87jd318
Join Date: Apr 2006
Posts: 11 Northern California
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2006-04-04          127204

Yes i believe so 300ci ....

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1990 f-150

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Peters
Join Date: Feb 2002
Posts: 3034 Northern AL
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2006-04-04          127208

It is a straight 6 isn't it? If it has vacuum advance I would also check the vacuum hoses. The my 83 had a mile and when it gets old it softens, it runs over the top of the engine and it can collapse under accelleration. ....

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1990 f-150

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SG8NUC
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2006-04-04          127214

I was looking for a 6cly to pull a bass boat. My mechnic told me there were only 2. The ford 4L and the Chevy 4.3L vortec. He said both were good engines, the ford would get 14mpg pulling the boat or not. I went with the chevy astro van no complants, a friend of mine bought the ford never had a problem but he only got 14mpg. At the time (1992)they were the only high torque 6's. I was wondering if this engine will get better milage now. ....

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1990 f-150

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87jd318
Join Date: Apr 2006
Posts: 11 Northern California
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2006-04-04          127218

Yes it is a straight 6. I will check the vaccum lines i was thinking this also. Thanks for your comments ....

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1990 f-150

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Peters
Join Date: Feb 2002
Posts: 3034 Northern AL
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2006-04-04          127219

My 18 got 14 mpg, but it was not fuel injected and was a 1 ton, long box, supercab. A friend had a small box van that was a little newer 85? with a similar set up, he was more like 19-20 mpg. ....

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1990 f-150

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oneace
Join Date: Mar 2004
Posts: 1490 south central pa
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2006-04-05          127264

As far as 6 cyl go. The 4.9L will out pull any 302 Ford and many Chevy 350 Ci. For mid size trucks and SUV you have the ford 3.0 and 4.0 in the Ranger and Explorer, the 4.0 HO strait 6 in the Jeeps. The 2.8 and the 4.3 in the Chevy/ GMC. The 3.9 in the Dodge. 3.4 DOHC 24V in the Toyota. Nissan also has them not sure of the size.

If I had to choose one I would go with either the Jeep or the Toyota. ....

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1990 f-150

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SG8NUC
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2006-04-05          127276

Oneace
I dont think that the 302 is a high torque engine, is the rest of the engines on your list hi-torque. ....

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1990 f-150

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oneace
Join Date: Mar 2004
Posts: 1490 south central pa
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2006-04-05          127279

The only engine that is classified as high torque is the Jeep 4.0L HO. I was simply listing the trucks and suv's that are available with 6 cyl. engines. But for all out torque you can't beet any strait 6. Look back at the dodge slant 6. You would be hard pressed to find another engine with that kind of pulling power back in those years. ....

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1990 f-150

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SG8NUC
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2006-04-05          127281

The reason I asked was the we pulled 20' bass boats and the foreign jobs or the 302 would not hold up. They were lucky to get 60 thousand miles out of them. The 4L ford and the 4.3L chevy 6s were out standing. My girl friend had a slant 6 in a plymouth valaint cant complain about its pulling power or hers. ....

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1990 f-150

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oneace
Join Date: Mar 2004
Posts: 1490 south central pa
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2006-04-06          127325

The 4L ford would have to have had a 5speed trans other wise? The auto trans. have a hard time making it past 60,000mi in normal driving let alone pulling a boat. Chevy is the same way with the newer 4L60E trans behind the 4.3L.

I have yet to see a Ford or Chevy of any kind out live a Toyota. ....

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1990 f-150

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87jd318
Join Date: Apr 2006
Posts: 11 Northern California
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2006-04-07          127372

Thanks for all your input,not sure what to make of it all. I have a 4.9L staight 6. 300CI 4x4 short box super-cab 355rear end ? What should i expect for mpg Ballpark? ....

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1990 f-150

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Peters
Join Date: Feb 2002
Posts: 3034 Northern AL
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2006-04-07          127381

I said you I got 14 mpg highway/city with a much larger truck. A similar sized van got 20. I used a friends the same year short box with auto and the 351 and it got 15 mpg. I would think you should be 17 or 18 average highway city. ....

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