Loud rattling noise at low RPMs (only under 2,500)
04-12-2009, 11:44 AM
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Loud rattling noise at low RPMs (only under 2,500)
Hey. I haven't posted here before, but I've been lurking for a while. 
Recently my S2k has started having a pretty bad rattle at lower RPMs. It's the strangest thing... I start the car and it sounds horrible. I start driving, and the second I cross over 2,500 RPM like clockwork, the noise instantly stops. Every time (driving or idle), it always silences exactly when the RPM exceeds 2,500.
*Videos w/ sound at bottom of post*
My roommate is far more of a gearhead than I am, so he's helping me try to diagnose it. We began by pulling the CEL's that started popping up. It was showing 5-6 codes, one for every cylinder misfiring, and two more miscellaneous misfire-related codes. We then performed a full compression test on all 4 cylinders, and they showed perfect compression. We thought it might be a valve adjustment issue, so we dove into the engine and checked the spacing. The gaps between all the valves were perfect.
After toying around with it, we ended up unplugging the two cables on the front left of the engine for VTEC, and the problem went away! I thought, "Okay, it's a vtec issue, I'll just keep it under 6k RPM and fix the vtec later." Well, within a day or two, the sound hadn't returned so we decided to plug vtec back in and see what happened. When we plugged it back in, the noise was still gone. Weird. It now appeared whether or not vtec was plugged in, the problem wasn't affected. Thinking back, I don't know the vtec system very well, but I didn't think it kicked in at all until 6k RPM... so I'm not sure how this would have affected anything. I kept driving it, and about a day later the problem returned. I checked my oil and found it was low again. I topped it off, and the rattle remained. Is it normal for an S2000 to burn through that much oil in just a few days?
Okay, continuing to diagnose after that... reading around S2ki, it seems the next logical step was the Timing Chain Tensioner (TCT). We replaced the TCT with a brand new one, and the problem went away again! Great, that fixed it, right? Nope. A day or two later, the problem came back, and we noticed noticed my oil was pretty low (but not causing any lights or anything). We topped off the oil, but the problem persisted, so we decided the TCT may have died again. This time I took the worm gear out of the new TCT and took it up to a local power coating shop to get it sandblasted. We tossed the sandblasted worm gear back into the TCT and reinstalled that in the car again. No luck- the issue is still there.
I took it by the dealership early on (big mistake), and they told me that rattle means my engine was shot, and they had some great prices for me to replace my engine with a brand new one (ha!).
So here we are today. I'm worried driving the car as-is may cause damage (the noise is loud and sounds pretty bad at low RPMs).
Anyone have any recommendations, or have had any experience with issues like this before? I appreciate any and all replies... I really want to get my car fixed again. Thanks!
----
Here are two videos I've uploaded two videos to YouTube showing the issue:
This one is from the engine bay, so you can hear the clear-cut starting and stopping of the sound as the RPM goes up and down:
[media]zr3lsu0W0nE [/media]
And this one is from the gauge cluster, so you can see the actual RPMs themselves going up and down, however from this angle it's much more difficult to hear the engine, so you have to listen closely to make it out:
[media]foVmeVcRrSA [/media]
Recently my S2k has started having a pretty bad rattle at lower RPMs. It's the strangest thing... I start the car and it sounds horrible. I start driving, and the second I cross over 2,500 RPM like clockwork, the noise instantly stops. Every time (driving or idle), it always silences exactly when the RPM exceeds 2,500.
*Videos w/ sound at bottom of post*
My roommate is far more of a gearhead than I am, so he's helping me try to diagnose it. We began by pulling the CEL's that started popping up. It was showing 5-6 codes, one for every cylinder misfiring, and two more miscellaneous misfire-related codes. We then performed a full compression test on all 4 cylinders, and they showed perfect compression. We thought it might be a valve adjustment issue, so we dove into the engine and checked the spacing. The gaps between all the valves were perfect.
After toying around with it, we ended up unplugging the two cables on the front left of the engine for VTEC, and the problem went away! I thought, "Okay, it's a vtec issue, I'll just keep it under 6k RPM and fix the vtec later." Well, within a day or two, the sound hadn't returned so we decided to plug vtec back in and see what happened. When we plugged it back in, the noise was still gone. Weird. It now appeared whether or not vtec was plugged in, the problem wasn't affected. Thinking back, I don't know the vtec system very well, but I didn't think it kicked in at all until 6k RPM... so I'm not sure how this would have affected anything. I kept driving it, and about a day later the problem returned. I checked my oil and found it was low again. I topped it off, and the rattle remained. Is it normal for an S2000 to burn through that much oil in just a few days?
Okay, continuing to diagnose after that... reading around S2ki, it seems the next logical step was the Timing Chain Tensioner (TCT). We replaced the TCT with a brand new one, and the problem went away again! Great, that fixed it, right? Nope. A day or two later, the problem came back, and we noticed noticed my oil was pretty low (but not causing any lights or anything). We topped off the oil, but the problem persisted, so we decided the TCT may have died again. This time I took the worm gear out of the new TCT and took it up to a local power coating shop to get it sandblasted. We tossed the sandblasted worm gear back into the TCT and reinstalled that in the car again. No luck- the issue is still there.
I took it by the dealership early on (big mistake), and they told me that rattle means my engine was shot, and they had some great prices for me to replace my engine with a brand new one (ha!).
So here we are today. I'm worried driving the car as-is may cause damage (the noise is loud and sounds pretty bad at low RPMs).
Anyone have any recommendations, or have had any experience with issues like this before? I appreciate any and all replies... I really want to get my car fixed again.
Thanks!----
Here are two videos I've uploaded two videos to YouTube showing the issue:
This one is from the engine bay, so you can hear the clear-cut starting and stopping of the sound as the RPM goes up and down:
[media]zr3lsu0W0nE [/media]
And this one is from the gauge cluster, so you can see the actual RPMs themselves going up and down, however from this angle it's much more difficult to hear the engine, so you have to listen closely to make it out:
[media]foVmeVcRrSA [/media]
04-12-2009, 12:40 PM
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I just updated the original post to include a clarification on the vtec issue.
Any other ideas?
So far I'm leaning toward replacing the timing chain tensioner AGAIN (@SgtB)... but I would like to get a few ideas for other possibilities first.
Any other ideas?
So far I'm leaning toward replacing the timing chain tensioner AGAIN (@SgtB)... but I would like to get a few ideas for other possibilities first.
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04-24-2009, 12:28 PM
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ah-ha! finally someone with the same exact problem/noise/issue i have! 
ive had this problem for a while, what ive done was injectors, valve adj, TCT, oil, and problem persist.
after posting for help ( https://www.s2ki.com/forums/index.ph...ic=661922&st=0 ) a guy name John (ComposiMo) pointed out that the 'shoulder' that the cam gear sits on is worn/broke. which causes the cam gear to not seat flat and could cause a little slack in the chain. but when the engine is rev'd high enough (2300-2500RPM) it pulls the chain to where its not slacking enough to cause the chain slap. very easy to check, just go to my thread.
the part isnt expensive at all, the catch is that to replace it, youll have to take the cams/shafts/rockers out. i havent done so yet, but i will soon enough..hope this helps, and dont waste another cent on a TCT, not yet ...
ive had this problem for a while, what ive done was injectors, valve adj, TCT, oil, and problem persist. after posting for help ( https://www.s2ki.com/forums/index.ph...ic=661922&st=0 ) a guy name John (ComposiMo) pointed out that the 'shoulder' that the cam gear sits on is worn/broke. which causes the cam gear to not seat flat and could cause a little slack in the chain. but when the engine is rev'd high enough (2300-2500RPM) it pulls the chain to where its not slacking enough to cause the chain slap. very easy to check, just go to my thread.
the part isnt expensive at all, the catch is that to replace it, youll have to take the cams/shafts/rockers out. i havent done so yet, but i will soon enough..hope this helps, and dont waste another cent on a TCT, not yet
...