87 f150 4x4, 4.9l, 4sp.

Truck starts easy and idles good but has low power, slow/no acceleration through the gears. This truck Should Rev up very quickly with lots of torque with low gears and bulldog trans.

I have changed spark plugs, Idle Air Sensor, cap, rotor, air filter, all fluids. Had to replace front fuel tank, both fuel pumps, fuel filter, also flushed fuel lines up to the injectors(truck parked for 5 years). Checked for vacuum leaks with ether, truck free-wheels easily. I'm confused why low power yet easy start and smooth idle? Check Engine light NOT on.

Any suggestions?

 

Do a compression check.
Also, look to see if you have a ratsnest or dead animal in the intake or exhaust. Voles love making old mufflers home.

 

waht exactly is your gear ratio, if you have 308 gears that would be about right in 3RD and 4TH gears if you have 410 gears somting is rong but your top speed will be slow with out running 4000 RPMs

 

thanks guys, will do a compression check and inspect intake, it needs exhaust badly but didn't want to spend money until motor is right. I checked the doorsill plate, axle code comes up as a 3.06 which seems high to me, but that trans is pretty low itself so it's hard to tell. I expect higher gears to be sluggish, but not first and second also. I just don't get why sluggish, but smooth with good start and idle. It literally seems as if when you press the accelerator Nothing happens.

 

is it sluggish, or is the clutch slipping?

 

I pulled a compression check, all 6 are within 3-4 psi of each other which is pretty dang good for 160,000.
I checked the intake and air plenum for blockage, nothing there.
I checked exhaust for blockage, none there because the cat is gone(I didn't know before) and the muffler is blown out(I knew that).
As I stated before, the truck from 2nd gear on while moving is sluggish(I can tell when a clutch slips. Clutch, pressure plate, throwout, pilot, slave cylinder, and master cylinder are all brand new anyway) as in Gutless.
I have an 88 model that is almost identical and although slow top end, it's very strong through the gears.
I need to find someone who can read OBD-I and see if emissions(cat gone but O2 sensor is there) or fuel is acting up.
I still doubt fuel because all but the injection rail is new, and it starts and idles too smooth for that.
I hope that this truck doesn't run this gutless naturally with this rear gear(again, 3.06). My 88 has 3.55 and is very strong 1-3. It shouldn't be That much difference.

 

my 86 has 2.73's, 3spd o/d, and is a real pig when in 0/d. if you try to put it in o/d any thing less than 50 mph, will actually try to stall.I spnd a lot of time shifting, but 20 mpg in town with a 300 6, I'm ok with that

 

3.08 gear could be your problom.
Make sure you have some exhaust there or your O2 may not get a good signal and artificaly rich it up.

No idiot light eh........Does it come on when the key is on without the engine running? If so the bulb is good.

Ford obd 1 is a great system but hard for a beginer to understand. Haynes has a discription in their 80-96 manual on how to conduct the test using a multitester or test light. Its in the engine electrical section.

If you own several ford obd 1 vehicles and intend on keeping them invest in an obd1/2 code reader. Make sure it has full obd 1 and 2 diagnostic. The 20 dollar pos at the hardware store is worthless. I paid $280 for mine and covers all the big three back to 80, and some gm and lincoln into the 70s! Plus you can get a ton of free beer looking up your buddies codes. I may be wrong but mine is an actron I belive.

Fords obd 1 can do cylinder output and drop tests. Allow for a zero timing and many other handy features for the gung ho engine tuner. It is actualy more versatile then obd2 and goes into greater detail.

 

Thanks guys. Between this forum and several people here I'm getting the impression it's the gear ratio. I've honestly never driven one this gutless, but it's too smooth otherwise to be anything else. Thank goodness for a bulldog gear.
The check engine light and the emissions light(it has one of those) comes on with the key on, but both go off when you start the truck.
I'm already shopping for a good OBDI/II reader.
I think what I will do is replace the exhaust including the cat and a new o2 sensor, and drive the wheels off of it. It'll be good for putting around, etc.
I'm disappointed, though, because I thought I had another good work truck. I will definately check the axle codes on all trucks from now on. I didn't know they geared one that high in a 4x4.
My 88 is still ok, but it has almost 270,000 on it. It has to lay down eventually.

 

my 87 4.9 used to do that to when all i had for exaust was nothin but pipe out to a tire burner and it used to lag like hell until i put a muffler on for some back pressure that may help if your exaust is shot

 

I know exactly what you mean. I am battling the same issue with my 95 m5od 2.73 against my fathers 94 m5od 2.73. Both have the same body and running gear. My fathers feels strong right off idle and smooth almost like a mild small block. Mine struggles off idle if you dont give it enough gas and just doesnt have the pull like his. Identical drivetrains and mileage but totally different in the power department.

 

300's are strange animals. My truck feels like a dog most days but sometimes my truck just comes alive and acts like a beast with very responive throttle. When my truck comes alive it's downright quick. But like I said most of the time my truck is a dog. This is the nature of the beast; 300's are moody animals. With a high gear ratio it's no powerhouse. However it shouldn't feel like a complete dog with the 3.08. I had a 3.08 gear ratio and my truck ran fine in the low end and ran like a champ in the top end. I could bottom out my speedo and just truck along.

What size tires does your truck have? Ford put a lot of 3.08 gears in 4x4 from what I see. I don't know why; no full size truck should come with anything less than 3.55, espcially if it's four wheel drive. 3.08 is great if you're looking for an econo-truck.

Sorry I couldn't help much. Just pointing out the 300 isn't fast but it's not slow and that your truck shouldn't be a complete and utter dog. It should have some speed to it.

With a 4.11 gear and close to OE sized tires my truck could do 0 - 60 in 11 seconds, bone stock besides gears and exhaust. This might give you some kind of idea.

 

thanks guys. due to work I've had to leave the truck alone for awhile. The truck has 31x10.50/15's which is only two sizes taller than stock(every truck I own has that size tire/wheel, it always works well). I've gone over the whole thing again tho, and can't really find anything wrong other than the exhaust which is in the works. I let a friend drive it, and he said that in 2nd/3rd/4th gear it felt to him like the truck was pulling something too heavy(very little and very slow throttle response). I checked all bearings(new and good), all brakes(new, not dragging), u-joints(a little play, but not worn out), trans and t-case(fluids new, very little play in gears), front and rear gears(fluids new, acceptable slop). I've heard everything here at home from weak coil and ignition to low fuel pressure to worn out throttle body to not enough air intake. None of these seem to be the case. I will just have to see if new exhaust(good back pressure) helps it. These trucks are pretty popular in the family/friends and I've driven them enough to know how it Should run. It Should be Strong 1st-3rd gear, OK in 4th up to about 60-65mph. With 3.06/3.08 gears(the axle code reads as either of those, depending on where you look it up), it should run a little faster top-end but should be gutless from 60-up.

 

I didn't read anything past what size tires you have. That's your problem. I have 31's with a 4.11 gear and my truck went from being quick to sluggish with the bigger tires. I would never want to drive an f-150 with the 300 with 3.08's and 31'' tires.

Either downsize your tires or re-gear your truck.

 

31's haven't been too tall on any other 4x4 I own/have owned, that's why I use them along with the fact that they fit any 4x4 without a lift. Yes they cause a Slightly higher gear ratio (5mph fast on the speedometer), but they have Never caused any of my pickups to dog down as bad as this truck runs. My '88 with 3.55 gears had 33x12.50's on it when I bought it and I almost couldn't feel the difference from stock 235's. I only changed them to 31's because they rubbed in sharp turns and then only after they wore out. You'd have to drive this truck, Bulldog feels like a normal 1st gear and 2nd-4th are Useless. On a straight, flat road it runs like a Yugo. It's an engine problem, I just have yet to find it. That's why I posted here after pulling out more of my hair than I can spare.