97 F150 4.2 Roaring PLEASE HELP

Hello all
I have a 97 F150 4.2 that is making a loud roaring sound from the engine compartment whenever the gas pedal is pressed even just slightly. It also sounds like the engine is revving up really quickly but, it could just be the sound is making me think that it is. The truck does not have a tach so I cant really tell for sure. It is also getting poor MPGs. The only code the computer is showing is 1038 which means IMRC is stuck open. However this code has been showing for three years and this noise just started last week. From what I understand the IMRC (Intake manifold runner control) is only to increase fuel economy at a certain RPM range. I would have had it fixed only my local mechanic wanted $1000 to do the job and I only paid $900 for the truck. The only problem I have noticed until now was a slight irradic idle from time to time But, otherwise the truck ran great. Before this noise started I was getting 17-20 mpg and now I am only getting 12-14 if I am lucky. If anyone has an idea as to what could be causing this noise I would greatly appreciate the input. Many thanks in advance for the help.

Hello all
I have a 97 F150 4.2 that is making a loud roaring sound from the engine compartment whenever the gas pedal is pressed even just slightly. It also sounds like the engine is revving up really quickly but, it could just be the sound is making me think that it is. The truck does not have a tach so I cant really tell for sure. It is also getting poor MPGs. The only code the computer is showing is 1038 which means IMRC is stuck open. However this code has been showing for three years and this noise just started last week. From what I understand the IMRC (Intake manifold runner control) is only to increase fuel economy at a certain RPM range. I would have had it fixed only my local mechanic wanted $1000 to do the job and I only paid $900 for the truck. The only problem I have noticed until now was a slight irradic idle from time to time But, otherwise the truck ran great. Before this noise started I was getting 17-20 mpg and now I am only getting 12-14 if I am lucky. If anyone has an idea as to what could be causing this noise I would greatly appreciate the input. Many thanks in advance for the help.
It sounds like you have a bad intake leak. Use some W-D40 and spray around anywhere you think may leak. When you hit a leak the idle should smooth out.

It sounds like you have a bad intake leak. Use some W-D40 and spray around anywhere you think may leak. When you hit a leak the idle should smooth out.


Well I checked for intake leaks and a found one small vacuum line that was broken. I repaired it but, it didn't make any difference. The truck is still roaring the same it is almost like a loud woo sound as soon as the gas pedal is pressed. Do you have any other suggestions or ideas. Thanks

Hello again,
It has been awhile since I posted this thread. I am still having the same problem. If anyone out there has any info or advice that might help me, Please let me know

I cant really afford to take it to a dealer or mechanic right now because I have been out of work for over a year with health problems. I am hoping I can find some help on here or find someone else that has had the same problem.

with the motor off, keys in your pocket. open the hood.
now find the fan give it a shake. if it moves replace the fan clutch.

If you have a vacuum gauge put it on the intake and get a reading. If it is less than 18 at idle and continues to go down the longer the engine runs you have a plugged cat or muffler.

Congratulations to Gremlin96, You totally nailed the problem. However I had already found the problem before I read your post. The fan clutch was locked up. I have not been online in a few days. I signed on to let everyone know I had found the problem when I saw your post. Thanks so much to everyone for all the help. Now I have a new problem with my wifes Explorer. I will post it later on. Thanks again