RyanL Posted January 31, 2012 Share Posted January 31, 2012 Over the course of the day, driving to and from school, I have noticed a hiss in the accleration of my truck (89'). The best way I can describe this sound is that it is similar to air escaping out of a pressurized bottle with a little "squeak" to it. The sound only occurs in the 2000-2600 rpm range. The two most recent activities that have occured on the truck was the replacement of the muffler and catalytic converter last Saturday, and yesterday afternoon I took the throttle body off to clean it and the IAC. Now I know the first thing that might come to mind would be vaccum leak right? Well the funny thing is the idle is fine. It idles between 800-1000 rpm in park with no roughness being transferred to the body, and 700-900 in drive under brake. Also the sound only occurs in drive under accleration or if I hold the pedal steady to keep the rpms in between 2000-2600. As far as I can tell it does not harm the truck in any discernable way (and hopefully never will :roll: ) Any help that could be given at this point would be very welcome. Thanks y'all Link to comment Share on other sites More sharing options...
Pete M Posted January 31, 2012 Share Posted January 31, 2012 what about a small leak somewhere between the TB and air filter? that could make noise but not really affect idle. maybe. :dunno: Link to comment Share on other sites More sharing options...
RyanL Posted January 31, 2012 Author Share Posted January 31, 2012 Air filter tube may not be secured tightly enough? Link to comment Share on other sites More sharing options...
cruiser54 Posted January 31, 2012 Share Posted January 31, 2012 New gasket installed under the TB after it was removed? Link to comment Share on other sites More sharing options...
RyanL Posted January 31, 2012 Author Share Posted January 31, 2012 Yes, the gasket was cut to fit and gasket maker black rtv silcone was applied to both sides Link to comment Share on other sites More sharing options...
MJRemi Posted February 1, 2012 Share Posted February 1, 2012 When you re-installed the IAC, did you make sure the O-ring was seated properly and was in good condition? Link to comment Share on other sites More sharing options...
RyanL Posted February 1, 2012 Author Share Posted February 1, 2012 Yes the IAC was relatively new and when I pulled it out it was also relatively clean Link to comment Share on other sites More sharing options...
Boots Posted February 1, 2012 Share Posted February 1, 2012 Your description sounds like when mine had an exhaust leak. You could have messed with something when you replaced the muffler... On mine the intake/exhaust gasket tore and pushed out near the front of the motor. It made a weird hissing/squeaking noise. Cracked headers are also common. :wrench: Link to comment Share on other sites More sharing options...
RyanL Posted February 1, 2012 Author Share Posted February 1, 2012 Ironically the header was repaired once already for cracks as you say. Also I did not previously mention but, the muffler is also loudest at the exact same rpm that the sound happens at. Tomorrow I plan on running the truck and spraying some carbuerator cleaner around the TB to check for leaks. If it doesnt change the idle then I think it might be safe to assume it is either a leak in the muffler or in one of the welds. A muffler shop down here mounted it because I don't have a welder so they should be able to fix it at no cost...(hopefully) :roll: As for the intake gasket it may have been aggravated when I pilled the TB off so if all else fails may have to replace it Link to comment Share on other sites More sharing options...
cruiser54 Posted February 1, 2012 Share Posted February 1, 2012 Check to see that your intake manifold bolts are snug. Link to comment Share on other sites More sharing options...
RyanL Posted February 1, 2012 Author Share Posted February 1, 2012 Check to see that your intake manifold bolts are snug. I will! :wrench: Link to comment Share on other sites More sharing options...
RyanL Posted February 1, 2012 Author Share Posted February 1, 2012 Well I just tried the carberatour cleaner and I came up zip for vaccum leaks. The truck is snugged up tight. I tried listening more with the hood open and it sounds like it is coming from somewhere around the fan belt but if it was a pully it would happen all the time right? I talked it over with my father (Akula69), and the best we could come up with was thermostatic clutch..maybe? :dunno: Link to comment Share on other sites More sharing options...
ICEBOX Posted February 2, 2012 Share Posted February 2, 2012 Do you have a cold air intake or a stock air box? I have a cheap air intake with cone filter and it hisses and wistles at higher RPMS Also get a mecanics thethascope and listen at each pully with it. Link to comment Share on other sites More sharing options...
Guanaco.13 Posted February 2, 2012 Share Posted February 2, 2012 New gasket installed under the TB after it was removed? Yeah my 89 MJ had the same noise and i replaced the TB gasket and it fixed the prob :wrench: Link to comment Share on other sites More sharing options...
RyanL Posted February 2, 2012 Author Share Posted February 2, 2012 Do you have a cold air intake or a stock air box? I have a cheap air intake with cone filter and it hisses and wistles at higher RPMS The airbox is the stock one that came with the truck. Also get a mecanics thethascope and listen at each pully with it. The airbox is the stock one that came with the truck. Where can I get one of those? Link to comment Share on other sites More sharing options...
RyanL Posted February 2, 2012 Author Share Posted February 2, 2012 New gasket installed under the TB after it was removed? Yeah my 89 MJ had the same noise and i replaced the TB gasket and it fixed the prob :wrench: Did the faulty gasket affect the idle at all? Link to comment Share on other sites More sharing options...
ICEBOX Posted February 2, 2012 Share Posted February 2, 2012 Ebay or you can make one pretty easy. I made one once out of exuahst tubing and a 5/8 straight fitting. little paint ahe it looked really good. Link to comment Share on other sites More sharing options...
RyanL Posted February 2, 2012 Author Share Posted February 2, 2012 Ebay or you can make one pretty easy. I made one once out of exuahst tubing and a 5/8 straight fitting. little paint ahe it looked really good. Sweet haha! Link to comment Share on other sites More sharing options...
MJRemi Posted February 2, 2012 Share Posted February 2, 2012 Harbor Freight sells them for $4. http://www.harborfreight.com/catalogsea ... tethoscope Link to comment Share on other sites More sharing options...
ICEBOX Posted February 2, 2012 Share Posted February 2, 2012 Oh snap. I thought he was asking about the air intake. sorry about that lol Link to comment Share on other sites More sharing options...
RyanL Posted February 2, 2012 Author Share Posted February 2, 2012 Harbor Freight sells them for $4. http://www.harborfreight.com/catalogsea ... tethoscope Thanks! :cheers: Link to comment Share on other sites More sharing options...
Guanaco.13 Posted February 3, 2012 Share Posted February 3, 2012 New gasket installed under the TB after it was removed? Yeah my 89 MJ had the same noise and i replaced the TB gasket and it fixed the prob :wrench: Did the faulty gasket affect the idle at all? I don't think it effected the idle, it started make the sound and I realized it was the coming from the TB and I removed it and saw the was bad so I changed it. Link to comment Share on other sites More sharing options...
RyanL Posted February 3, 2012 Author Share Posted February 3, 2012 New gasket installed under the TB after it was removed? Yeah my 89 MJ had the same noise and i replaced the TB gasket and it fixed the prob :wrench: Did the faulty gasket affect the idle at all? I don't think it effected the idle, it started make the sound and I realized it was the coming from the TB and I removed it and saw the was bad so I changed it. Do you cut your own gaskets or buy them new? Link to comment Share on other sites More sharing options...
Guanaco.13 Posted February 3, 2012 Share Posted February 3, 2012 New gasket installed under the TB after it was removed? Yeah my 89 MJ had the same noise and i replaced the TB gasket and it fixed the prob :wrench: Did the faulty gasket affect the idle at all? I don't think it effected the idle, it started make the sound and I realized it was the coming from the TB and I removed it and saw the was bad so I changed it. Do you cut your own gaskets or buy them new? I buy new ones, I got a felpro gasket for it Link to comment Share on other sites More sharing options...
RyanL Posted February 3, 2012 Author Share Posted February 3, 2012 New gasket installed under the TB after it was removed? Yeah my 89 MJ had the same noise and i replaced the TB gasket and it fixed the prob :wrench: Did the faulty gasket affect the idle at all? I don't think it effected the idle, it started make the sound and I realized it was the coming from the TB and I removed it and saw the was bad so I changed it. Do you cut your own gaskets or buy them new? I buy new ones, I got a felpro gasket for it Oh I see..we cut ours from gasket maker material so if I cut it wrong or punched the holes incorrectly that may be the problem Link to comment Share on other sites More sharing options...
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