Truck makes a loud humming sound at idle
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Truck makes a loud humming sound at idle
I have a '99 f150 XLT 4.6, sometimes it makes a very loud humming sound, then I give it gas and it goes away. It only does it in the cold weather. I do have a K&N intake system, could that have anything to do with it? Someone help me out because it drives me crazy and I cant figure out why!!
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My 98 5.4L has been doing that for as long as I can remember , just after I shut down the EVR will humm for a bit - for about 8 seconds or so.. After I shut down the EGR valve closes (no more vacuum) and EVR vibrates and humms until the trapped air is expelled..
I don't think it's hurting anything , truck runs great, so I pretty much just leave it alone
I don't think it's hurting anything , truck runs great, so I pretty much just leave it alone
Last edited by jbrew; 03-18-2007 at 09:16 PM.
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1. Try pulling your PCV valve and shake it , if it sounds like an empty paint can then it's good - if questionable , just replace it - it's only 3-6 bucks and this has been known to cause this problem.
2. Sounds air/vac related. Start your truck, let it run for 30 seconds, have your hood open before you start it. Shut the truck off and go look under the hood quickly - do you here a noise like air releasing?
3. Check the vac line behind the manifold at the 90 - this has been known to collaps/leak and could be making the noise at a certain RPM's.
Heres a pic of that line , the 90 by the firewall is the one that I'm talking about -
2. Sounds air/vac related. Start your truck, let it run for 30 seconds, have your hood open before you start it. Shut the truck off and go look under the hood quickly - do you here a noise like air releasing?
3. Check the vac line behind the manifold at the 90 - this has been known to collaps/leak and could be making the noise at a certain RPM's.
Heres a pic of that line , the 90 by the firewall is the one that I'm talking about -