Tried everything you guys have offered, everything checks out good. All the sensors, everything. And then this happens....

Im heading to the part store, truck still just making the "wooshing" (it sounds like my fan turning 100mph) noise from under the hood under fulll throttle. I leave the parts store, on my way home, and I get pissed and decide to flog it. I spin the tires gun it up the road and the "wooshing" noise slowly fades. The truck for no reason started running great agian. I could hear the motor rev up, it was quiet, grumbly, and I didnt hear that annoying sound anymore. I parked the truck and revved it up some more, and I could actually hear the motor for once!!! It was running so perfect and driving great. So heres the bad news....I get out and touch the throttle to rev it up from under the hood to hear the motor running at its peak, and INSTANTLY, THE SECOND I TOUCHED IT, it goes back to making that noise again!?!?!?!? I just TOUCHED, TAPPED, PUT my finger upon the throttle cable and the truck instantly ran like **** once more. So I took the truck back out,l beat on it some more, and for heavens sake it started running good again?????. It stayed running good until I just lightly touched the throttle under the hood, and bam, instant crap mobile again.

WHY IS IT DOING TIHS!!!!!! Its stayed running like crap since then, and I cant figure out whats going on with it!??!?!

Do I have a problem with my throttle cable!?? Or the setup on the throttle body!?? I mean, the truck can be running great, but the instant I touch the throttle from underneath the hood, it goes to crap.

 

crappy IAC. it may be leaking. or it could be the TPS.

 

But why would it go out as soon as I touched the throttle by hand?? Wouldnt it do the same as if I was modulating it with my foot on the gas pedal??

 

something loose. Make sure that gasket is good on the IAC make sure things are tight make sure that everything is at the right torq settings the throttle body is 12 to 14 ftlb so yea check those.

 

seemingly if it runs good under full throttle then it would be one of the actuators may be stuck in the position ideal for that mode of operation: like for ex. the egr stuck closed,or Iac stuck open.

 

You can always drop the truck and the title off at my house...

 

is this on the 91 302?? check to see if the throttle body is loose,,make sure the manifold is not loose to the upper plenum, look for anything at all that could cause a vacuum leak. check the mass airflow sensor. see if the air intake is connected, or loose.

 

You say you hear a WOOSH noise and you think the fan is running fast. That just may be what is happening. You didn't say if you truck had an electric fan but since your in this forum I suppose you have a engine driven fan.

That fan is run by a clutch that is liquid filled and when they go bad the clutch engages at very low rpm and won't disengage until it wants to (like a bad child). The result is a hell of a lot of noise and the engine loads due to lost HP thus you think the whole thing is going to blow up.

you can verify the above by trying to turn the fan by hand with the engine OFF and the key in your pocket. If it is even does not free wheel with a cool engine, the clutch is shot. If it is even partially difficult to move--the clutch is shot.

If that is what is happening, go back to the parts store and buy a new fan clutch. Remember to keep the key in your pocket while working on the fan.

 

Well, its not as if its "difficult". I can spin it with one finger. But it does take a little bit to turn, which I'd expect. It shouldnt free spin easy should it? This is something I might look into more.

 

I didn't even think of that Pacam, but I have a friend who's dads F250 had a frozen Radiator fan, and it felt like it had no power (5.8). It wouldn't turn off because the clutch was gone, so it ran like it was pushing against a wall the entire time. Look into that bsmotorsports.

 

When my engine is still cold, I can actually stop the fan from turning. It should be pretty easy to spin by hand while cold.

 

i was gonna say no but now that i think about it. . . i can spin the fan on any new car easily. a lot more easily than my trucks fan. maybe mine is shot too lol. . . that WOULD probably quiet it down wouldnt it? hmm . . . good thread

 

You've put your hand in a moving truck fan? For the love of god please let me shake your hand. where do you get your pants they gotta hold a lot of weight from the pair you got.

 

I'm not sure if my truck is doing the same thing or not, but the more I read your post the more it sounds like it might be. I also hear the noise that I think you are describing. It appears out of nowhere and goes away just as mysteriously. Sometimes it does it everyday for a week or two. Then it will go away for several weeks before it reappears.

I have determined that my problem has something to do with the alternator. While it is making the noise my battery guage shows that it requires much higher RPMs to charge properly...it charges but I have to rev the engine up. When I begin driving the needle points to the low end of the guage. When the noise stops, usually after 5 or 10 minutes of driving, the guage immediately jumps back up to where it is supposed to be.

I don't know if this has anything to do with your problem or not but it might be something to check. Good luck.

 

I believe I have found my problem. I looked in my haynes manual and tested the fan clutch every way they described. It failed all the tests basically. The truck seems to run like its pushing a wall, exactly like you explained when the fan does this, and the fan wont disengage at all. It never quiets down, no matter what rpm Im at. Im going to go to autozone and pick one up.