randompacking

I have a 2005 Scion tC. The engine makes an odd noise at idle (drive or reverse, not park)at about 600 rpm. This is more prevalent during cold weather (<45°F). At rpms greater than 800, the whining goes away.

Please help me identify the issue with my engine.

Below is a link to Youtube for a recording I made in a parking garage. at 27-38 seconds, I pressed the pedal to get the Rpms to be around 800 and the sound went away. you may need to turn up the volume to hear the sound clearly as the recording is not great.

Thanks for your help.

randompacking

no ideas?

samatman

I'm not an expert on this kind of stuff but here you go... When I read your post I assumed it was a tranny problem and I can't help with that. But now that I've listened to the noise it almost sounds like a bad motor mount. Very low RPM noises can be caused by a lot of things, heat shields, exhaust hangers that are breaking, things in your glove compartment, etc. Can you see the engine shake more than normal below 800rpm?

randompacking

thanks for the insight. I hope to pop the hood this weekend and see how the engine acts during low rpm.

question: how can i tell if it is the engine mount when performing this test?

randompacking

I tried to record the engine (while shifting through the autotransmission settings) this morning. Unfortunately, this morning was slightly warm at 60°F and the annoying sound was not there. Also, I went driving to do some errands immediately afterwards and never heard that problematic sound while at a stop sign or at a red light. I think the weather is supposed to get colder later in the week, so I hope to try again.

Here is the video, shot on a tripod.

p-->r 0:23
r-->n 0:28
n-->d 0:33
d-->n 0:57
n-->r 1:04
r-->p 1:12

I don't think the engine moved that much to indicate an engine mount issue, but I don't know for sure.

Thanks again for helping me out with this.

randompacking

one more thing. During the video, the lowest the rpm went was maybe 800-900 rpm, while the odd engine sound would typically occur at 600 rpm while driving. But, while I was driving today immediately afterwards, at stop signs and red lights, the rpm did get down to 600 rpm but there was no odd engine sound.

samatman

I agree, everything seems to be pretty normal in the second video. Hopefully someone else has more insight into this.

udelslayer

There is a heat shield on the s-pipe that can be loose, but it sounds reminiscent of what the radiator mount begins to sound like when that rubber gets harder. It could be the serpentine belt tensioner. Use a stethoscope or a long funnel or a paper towel roll core to listen to specific areas to pinpoint where the sound is coming from. It sounds normal in the second video.

Is your pcv OEM?

randompacking

Thanks for the tips. i will try to pinpoint the sound with a tube or something.

PCV valve is still the stock one. I haven't replaced it yet.

So, this morning was cold (45°F), so i decided to do a video this morning instead of tomorrow. The video is the first start of the day. I cycled between P-R-N-D settings mulitple times. The rpm started around 1500 and then settled closer to 900 at the end. The odd noise started at around 2:32 shift (to drive or reverse, i forget). I still didn't see anything super odd to cause the noise.

udelslayer

Make sure to use the OEM PCV. Aftermarket ones cause it to sound like a unicorn coughing.

Remove your heat shield and check for leaks. Check for leaks or loose things. You should see black marks. When the motor pitches forward is when the sound is most pronounced. Check the exhaust donut. To me, it sounds like air pressure rapping a dull sound on metal.

I'd think that that if you had that much of a leak though, you'd throw some kind of cat code.


The rubber tube trick will help.

randompacking

"unicorn coughing". that is hilarious.

is the heat shield the black plastic on the engine or the curvy metal piece just next to the engine?

udelslayer

Up top is a plastic is a cover over the spark plugs. Its worth removing and having a look. its more cosmetic and held down by two 10mm nuts. While I dont think a plug is loose, I have seen motors that had loose spark plugs and lost compression up the valve cover.

The metal cover on the front which is held on by 3 bolts and a nut on stud is the exhaust manifold heat shield. It can be removed (just dont do it hot) and you can run the car to look at the exhaust runners and look for leaks, etc. You should be able to fish it around the o2 sensor wire without having to remove it in most cases.

I think the sound is always there, but I noticed that when your motor pitched forward around 2:32, the sound was more pronounced. There is an exhaust donut at the bottom of the manifold thats easy to see that could be leaking but like I said, its hard to tell from a video.

randompacking

thanks! i will look for that.

i think my next step is to pinpoint the actual location of the noise. i will try to do that next time the weather gets cold again.

thanks for everyone's help! you guys are awesome.

udelslayer

You can get an automotive stethoscope from Harbor Freight (or amazon) for under $10. Its a very useful diagnostic tool for this kind of thing...and more.

randompacking

Thanks! i will look to buy one.