[updated:LAST EDITED ON 05-Jan-02 AT 07:06 PM (EST)]I have a 1996 F-150 4.9L 300 with 106,000 miles on it. Everything has been running very smoothly lately. However in the past 2 weeks, my check engine light has come on. It has come on before, and I do a routine check of fluids and pressures and it turns off in the next week or so. I dont know if it is due to the colder weather, but now there are other problems with it as well. I will list them below:

1) When idling for a while, a sound comes from under the hood. Its not a whistle, its a mechanical buzzing humming kind of noise. Hard to explain. When I rev the engine a bit it goes away and doesnt last more than 10 seconds when it happens.

2) At higher speeds (65 - 70) the truck starts to shake a bit and feels funny in general. I recently put bigger tires and wheels on it (not sure what the stock size is for my truck) they were off my dad's 1987 F150 custom 4x4. They say 32x11.50R15LT on them. Dont know if its hurting my axles or anything. Its been driving fine until recently, could be the engine shakin.

3) People tell me I need to do a tune up on my truck. I change oil spark plugs fuel filter etc. Ive never replaced O2 sensors, or anything else on the truck as nothing has gone wrong so far (knock on wood). First thing that has broken was the emergency brake cable and that was a month ago. What exactly goes in a tuneup?

4) Although I know its not the best thing to do, when i first got the truck I could spin the tires in 1st easily and 2nd on occasion. I didnt do it all the time, just sparingly back when my truck had some getup. That lasted for about a year, now I cant spin the tires in granny gear in rain. What has robbed all my power?

5) I noticed about a year ago that some dirt had somehow crept into my coolant resevoir, so I flushed the coolant and put new in. Now there is dirt in it again. Looks like dirt you use to fill in holes in your backyard. Tan colored. Do I have a hole somewhere or is that common?

Anyway this is long and boring, any help is appreciated. Thanks!

 

[updated:LAST EDITED ON 07-Jan-02 AT 01:02 AM (EST)]>1) When idling for a while, a sound comes from under the
>hood. Its not a whistle, its a mechanical buzzing humming
>kind of noise. Hard to explain. When I rev the engine a
>bit it goes away and doesnt last more than 10 seconds when
>it happens.

After further investigation I have figured out the noise only happens after the engine is warm. I still have no idea what the sound is.

 

The larger tires are probably robbing some of you power. I noticed that putting 31x10.50x15 BFG's on my truck did that some, so I changed the gears in the rear end from 3.08 to 3.55. The stock tires are probably 235 75 15. The tires could also be part of your vibration. Does the whole truck shake or just the steering wheel or both?? They could be out of balance or worn funny due to alignment. The vibration could also be torqe converter shudder in the tranny. This is fairly common in these trucks. Autotrans makes a shudder fix circuit broard that you put in the trans. It increases line pressure and does a few other things but I can't remember off the top of my head. I used it in my 95 F150. I think its a pretty good thing for about 60 bucks. My truck shifts better than before. I would check the tires first though.

As far as a tune up goes... You should replace the plugs, wires, distributor cap and rotor, air filter, fuel filter, pcv valve, oil breather, and O2 sensor. You don't need to replace the O2 sensor every tune up but since it hasn't been replaced you should. It could be causing your check engine light to be coming on. It is one of the first things to cause that. I would also service the tranny if that hasn't ever been done. Replace or inspect the belts and hoses if they are original.

I'm really just a do it yourselfer but I hope this helps a little.

 

I have your exact truck, minus 10,000 miles.

I have a buzzing sound, kinda. I just think it is my compressor kicking on and off occasionally. When you rev the engine, it goes away...because the engine is now louder than the sounds?

The big tires may shake the truck. I have brand new 33's, balanced and all, but they ride like a dream, so I'm not sure.

Tune ups help...but you need to do the O2's. Your truck should have three, maybe four. Two in the engine compartment. One or two in the cat converter.

Problem is, they're expensive as a mother. But when your engine light comes on and they ARE the problem, your truck may barely run at all...this happened to me, I know. I replaced one and it immediately cured it. I would replace them all if you can afford it. You will be thankful. And you won't need to again for another 60,000 miles plus. Make sure you get the right ones, though, they're all different, even on the same truck.

My coolant reservoir is dirty, too, but I don't think it is cause for concern. Was the coolant itself dirty when you drained it?

-Nick.

 

What you might be hearing is the electronically controlled solenoids that manage the AIR & Egr . When they vent they make that noise . Do you hear it when you shut the engine off . My 4.9L does the same thing only I hear it when I shut the engine off , It last for maybe 5 to 10 secs . Youll need an OBD II Scan Tool or Code Reader to check for any stored trouble codes , It may be that one of those solenoids is malfunctioning .

 

I dont hear the sound when i turn off my engine, its only when its warm and i come to a stoplight or something. When I barely press on the gas and it revs a little bit the sound get quieter... not cause of engine noise, it actually gets quieter but its still there.

How can I go about switching out the rear end of my truck with a diff set of gears? How much does that set me back money wise and what difference would I see? Diff shifting speeds etc?

Im not definite what is causing the dirt in my resevior but it kinda scares me. Im going to replace all the stuff you guys mentioned. Not sure about O2 sensors, you say they are expensive, are we talkin 100 or 200 bucks? Or like 50 - 75? If the O2 sensor is bad does it rob performance from my truck? If so that might be my problem on the performance end.

Im going to put a code tester to it tommorow and see what comes up. Im also gonna apply that tech article to my speedometer... im about 5 - 8 mph off thanks to the bigger tires. After that Ill be nice and tuned up and hopefully going good. Im gonna get my uncle (mechanic) to check out my tranny. As long as I help he doesnt charge me. :-) Good to get my hands dirty. Just those last few questions then im done! Thanks!

 

The oxygen sensor could definitely be robbing some of your performance and could also be causing a drop in gas mileage. It should cost about 50 bucks.

With a change in gears your truck will shift a little sooner, and you will definitely notice that the truck will have more get up and go. You will also be able to tow more depending on what ratio you go to. What gear ratio do you have right now? If you have 3.08 then I would go with 3.55. That's what I did. If you already have 3.55 then 3.73 would be a good choice. I wouldn't go any more than 4.10 gears though then you will get worse gas mileage. I did that in my previous 95 F150 with a 4.9 6 cyl. It was A LOT more responsive though. LOL... I beat a 91 Camero RS 305 with it.

There are a few ways to go about changing your gears.
1. You can go to a shop that does differential work and have them put in. This can get expensive.
2. You can buy the gears and do it yourself. This wouldn't cost you too much probably about 150 $.
3. You can go to a salvage yard and get a rear end out of a different truck and trade yours for it. The cost of this can vary you would have to ask the salvage yard.

 

But just how tough of a job is changing gears?

Is it a one-person job, and if so, it would require about how many hours? Are specific tools, gear pullers, bearing setters, special tools, etc. needed?

I'm hoping to do mine this spring or summer to counter my 31 inch tires on what I swear is a 3:08 or even higher rear-end. I can't stay in fifth gear on the highway once i hit hills (even if I have a speed of 75 MPH going in to it). And reverse is just way too fast once i let the clutch out.

 

Right now im 99% sure I have a 3.08 rear end. My uncle is a mechanic and he can help me put in the new gears. Free labor when I help! :P

I have a 5 speed, and I have noticed lately too that I cant stay in overdrive without losing speed on overpasses. (A strong wind completely kills me) Suprisingly I can get my truck from 0-60 in about 13 - 14 seconds. Im not even trying that hard. I dont think thats too good but for ~145 horsepower stock im happy!

That little buzzy noise is coming from the engine. I had my dad listen to it, he think it might be the fan clutch? I dont know if he knows what hes talkin about

Ok so replace O2 sensor, change out rear end, tune up. I hope to have my tourqey baby back soon! This summer im gonna put some 31s on it. I have 32x11.5s now and they are a lil too big and wide.... rub a little in the front on deep dips and stuff.

Thanks for the help!

 

4 oxygen sensors?? Are you sure about that? I have a 95 F-150, 300 I6 and a 5 speed, and I see only one. Bosch only shows one for that application.

 

Fish462, The other two are located one each on the exhaust manifolds. They are called o2 monitors and look just like the o2 sensor with a price to match. I had to replace all 3 to get my engine light to go out. Ford mech mentioned a problem recall on the o2 sensor mounted on the cat. On some truck the air-conditioner condensation would drip and blow back on the sensor. The sensor would then short out and die.$$$$$$$$ The fix is some kinda hose to redirect the drip.

Chris

 

Justin, I have same truck. When mine idles by far the loudest noise is the power steering pump. WWWWWWWWHHHHHHHHHHRRRRRRRRRR

I would like to hear it without the pump noise. I'll bet Nice and quiet.

I bought mine used. My radiator overflow tank was dirty also but mine looked like oil or black coffee goo. When I did a radiator flush things cleaned up. That is when I noticed the sides of the radiator are plastic and are sealed with a rubber o-ring and crimped metal tabs. Mine began to leak around that seal on a drive from Alabama to Ohio. Not wanting to use any radiator stop leak? I did anyway. Now my recovery tank looks just like when I bought the truck. The stop-leak stuff seems to collect there. The cap on that resorvoir fits kinda loose too. Maybe some mud found it's way in on yours?

Chris

 

My truck doesn't idle very well, but I have no check engine light and my gas mileage and power are good. I figured when I reached the 100K mark I would tune it up again and change the O2 sensor. A mechanic friend suggested I let him clean the fuel injectors. I need to check the idle speed as well, it seems to idle high which may be due to a vacuum leak.

 

the "dirt" in the radiator may be oil in the antifreeze.
mix oiland water aand you get a tan goop!!
this can mean a head gasket leak or cracked block or head.

 

I had a similar problem with my 96 (5.8L). It would surge through the parking lot at just above idle and chug going up hills in OD until it shifted into Drive. The problem was the EGR relay. About $35. Try unplugging the green vacuum hose going to the valve and see if it goes away.