Exhaust noise...sounds like when a fast motorcycle slows down and has that bubble...

[jimdigs]

sounding gargle in the exhaust. boom diddy boom boom.
Why would my exhaust be sounding like this? I just rechecked my timing. Grounded out the STI, my RPMs are steady at 700. Checked my timing and its a bit above 10, maybe 12-14, with a timing light.
Thanks in advance.

[WmWatt]

Do you have a vacuum guage? I'd clean all the ignition wires, cap, and rotor, clean and check gap on sparkplugs. Easy and costs nothing to do.

[jimdigs]

I do have a vacuum gauge. I'll throw that on and look for what? The exhaust plugged up? If I remember right don't you snap the throttle and watch the gauge to see if it goes up and snaps back down, something like that?

[Movin]

Maybe it is not staying in decel fuel cut, or cutting fuel at all during decel.

[WmWatt]

Yeah, slow restoration of vacuum can be a plugged exhaust but vacuum guage will also show engine miss. There's a "sticky" permanent article at the top of this webpage which lists vacuum guage diagnostics. It's the first thing I try when the engine sounds funny.

[jimdigs]

I put my vacuum gauge on and it held steady just above 20. Plus when I flicked the throttle it acted as it should and went way down to 0 quick then above 20 and back down to 20. Any other thoughts?

[WmWatt]

Something loose inside catalytic converter or muffler? Hard to say without hearing sound. Try tapping on exhaust components? Place hand at tail pipe and feel for change in exhaust gas pressure?

[jimdigs]

Something loose inside catalytic converter or muffler? Hard to say without hearing sound. Try tapping on exhaust components? Place hand at tail pipe and feel for change in exhaust gas pressure?

The exhaust does sound louder too. Thanks for trying to help with this WMWatt it is appreciated. I'll try tapping around stuff.

[sketchman]

My B6 swapped car does this too. Though I'm still getting 40mpg and it runs great, so I haven't worried about it.

I wonder about the thought of it not doing decel fuel cut as Movin suggested. Could be as simple as a TPS adjustment. Maybe if the TPS isn't sending closed throttle and the ECU sees RPM still up while it's coming down it's not completely cutting fuel.

[tooldude]

^seems most likely.

[jimdigs]

My B6 swapped car does this too. Though I'm still getting 40mpg and it runs great, so I haven't worried about it.

I wonder about the thought of it not doing decel fuel cut as Movin suggested. Could be as simple as a TPS adjustment. Maybe if the TPS isn't sending closed throttle and the ECU sees RPM still up while it's coming down it's not completely cutting fuel.

I'll test the TPS. Thanks.

[jimdigs]

Ok, so today I put the vacuum gauge back on because when I thought I was checking for exhaust by snapping the throttle it was not what I was needing to be doing. Supposed to keep it reved up to 3000 and keep it there and see if the vacuum gauge stops dropping at the steady 3000, if it does drop then you have a clogged exhaust. Well, I did this and everything looks good. But when I place my hand over the muffler I barely feel anything coming out?!?!? Everything checks out great according to the gauge but my exhaust is clogged somewhere. What say you?
I did not test the TPS yet. I will if I can't figure out this exhaust thing. I did try tapping on the exhaust and muffler but didn't hear anything out of the ordinary but really don't know what that would be, maybe something loose sounding.

[WmWatt]

Try unbolting the mufler from the tailpipe? They say to unbolt the catalytic converter from the exhaust manifold but unless it's relatively new I think you'll find the heat has rusted the nuts and putting pressure on would probably break something. Be careful with the muffler nuts as well. Penetrating oil overnight might help but beware running the engine would burn it off. Not difficult. I've changed my own muffler. I've also taken the muffler off and tapped the rust out and put it back on.

[sketchman]

Did you test the TPS? I just did mine. It was off. Going to test drive it in a few, and I'll report back if it fixed it or not.

[jimdigs]

Did you test the TPS? I just did mine. It was off. Going to test drive it in a few, and I'll report back if it fixed it or not.

Yes I did. It was fine. Continuity where it was supposed to be.