SoloCamo Posted December 21, 2008 Share Posted December 21, 2008 Hey all... Recently my 4.0L (133k on the clock) has been making a slight knocking noise at idle, that would increase with the RPM's. It wasn't obnoxious and was hardly noticeable when on the road. This would seem to come and go but has became more consistent lately. However, lately under hard acceleration I noticed a very odd and distinct "chopping" sound coming from the engine bay. As if the air is being "chopped" as it gets sucked into the TB. Under normal acceleration it is slightly noticeable, but it becomes extremely present under harder acceleration. It does it 9/10 times as well, so it is very consistent. Possibly a cracked exhaust manifold? I noticed a very slight power loss as well. Any ideas would be greatly appreciated! :chillin: Link to comment Share on other sites More sharing options...
deziped Posted December 21, 2008 Share Posted December 21, 2008 Mine had those symptons when the motor mount broke. Lost power do to engine flopping up & down. :dunno: Link to comment Share on other sites More sharing options...
BLHTAZ Posted December 21, 2008 Share Posted December 21, 2008 How's the oil pressure? Pull the valve cover and check for broken valve springs...this happened to mine. Link to comment Share on other sites More sharing options...
SoloCamo Posted December 21, 2008 Author Share Posted December 21, 2008 Oil pressure gauge = shot. However, I just did an oil change with some Castrol GTX High Mileage 10w-30. Same stuff I've used for all my other changes in the past. This time however, I didn't realize I was a little less than half a quart low due to an increased oil leak and ran it like that for a few days. It has since been topped off. :ack: I wouldn't think being slightly low like that would cause problems, would it? :dunno: I really hope it's nothing internal, as I don't have the tools, time nor money to fix it. :wall: Link to comment Share on other sites More sharing options...
knightrider Posted December 21, 2008 Share Posted December 21, 2008 This might be too obvious, or I could have misread, but have you checked the radiator shroud/elelectric fan and engine cooling fans to make sure they aren't hitting anywhere. This could be where the chopping sound is coming from....... If you have a broken motor mount, could be letting the engine torque to one side, thus the hitting of a fan on the shroud..... Just my .02 Link to comment Share on other sites More sharing options...
Oizarod115 Posted December 22, 2008 Share Posted December 22, 2008 running half a quart low shouldn't be noticeable at all, or harm anything. a busted manifold is going to be loud and obnoxious and also really obvious if you stick your head under the hood. Link to comment Share on other sites More sharing options...
SoloCamo Posted December 22, 2008 Author Share Posted December 22, 2008 running half a quart low shouldn't be noticeable at all, or harm anything. a busted manifold is going to be loud and obnoxious and also really obvious if you stick your head under the hood. You see, it's like a small ticking also, and it sounds like it's coming from the valve cover/manifold area, except with all the other parts going (mainly the clutch fan) I can't really tell. I did have to tighten one of my exhaust manifold bolts though as it was pretty loose, however that was before the noise came into play. I also noticed tonight it barely did it unless about 3/4 on the throttle. It almost sounds underneath me, but again when driving it's extremely hard to tell. I also hear the "ticking" from the exhaust when idling. Link to comment Share on other sites More sharing options...
deziped Posted December 22, 2008 Share Posted December 22, 2008 Just turn the stero up & drive. Link to comment Share on other sites More sharing options...
SoloCamo Posted December 22, 2008 Author Share Posted December 22, 2008 Just turn the stero up & drive. That's all fine and good for you (and foolish to say the least), but I prefer preventive maintenance over being stuck out 3 hours from my house because I ignored a potential problem. Link to comment Share on other sites More sharing options...
SoloCamo Posted December 24, 2008 Author Share Posted December 24, 2008 Small update: Motor mounts are in good shape, and under throttle it was not moving enough to cause the fan to hit anything. So that's one down. :chillin: Under further inspection and some long driving it seems that my catalytic converter is on it's way out. It wasn't doing it nearly as bad today and I was revving it quite a bit trying to get the sound. However, when I got home tonight from work I noticed quite a rattle from the middle of the truck. Went underneath with it running and it definitely sounds like something is loose in the exhaust, and the sound is coming from the general area of the cat so I'm assuming it's the cause so that will be my first step. Drivability is fine and I believe the loss of power was all in my head to be honest because it felt great today. Link to comment Share on other sites More sharing options...
Geonovast Posted December 24, 2008 Share Posted December 24, 2008 I would turn the motor by hand with a ratchet to see if you can hear and clinking inside. That might tell you if something's loose inside. Wouldn't hurt to pop the valve cover off when you turn it to see if any of the valves are sticking. Link to comment Share on other sites More sharing options...
BLHTAZ Posted December 24, 2008 Share Posted December 24, 2008 If the cat is going bad, the loss of power is not in your head. It will get worse and eventually the truck will not even run when the cat clogs up completely. The meduim inside is breaking loose little by little and it will get blocked sooner or later...again...IF the cat is going bad. Sounds like a good possibility to me from your descriptions though. :thumbsup: Link to comment Share on other sites More sharing options...
SoloCamo Posted December 24, 2008 Author Share Posted December 24, 2008 If the cat is going bad, the loss of power is not in your head. It will get worse and eventually the truck will not even run when the cat clogs up completely. The meduim inside is breaking loose little by little and it will get blocked sooner or later...again...IF the cat is going bad. Sounds like a good possibility to me from your descriptions though. :thumbsup: Well for the longest time I've also noticed that my exhaust will sometimes sound like a Bass that can't handle the load so to speak. That sound when you pump a small bass too loud and it makes a "wahhh" sound. So with that also as evidence I'm going to replace the cat anyways. If it solves my problem, then great. If not, hey a new magnaflow high-flow cat can't hurt. :thumbsup: Thanks for all the help so far everyone! Much appreciated Link to comment Share on other sites More sharing options...
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