Exhaust problem?

[rendyx]

This began after doing my upeer 60k yesterday. I've noticed it has gotten worse today, the exhaust sounds very rough (bummppphh, bumph, bumphh, bummpphphhhh, bumph, bumphhhhhh), and seems to "skip" a lot. Now one thing I am considering is that the t-stat must have been bad for some time, as replacing it made the heat up quickly, and always do so, not just some of the time. I drove for an hour yesterday, and it never got above "C."

Is it possible I have killed a cat, and it is falling apart? I know I have bad mufflers, but it doesn't seem like they'd cause htat, or even for the floor to shake a bit with the skips. The motor seems to run fine, it slows a tiny bit with the sound, but perhaps whatever is causing it is just affecting the motor too. The sound is definately from the exhaust system.

I may take a better look under there tomorrow and see if there's anything obvious (holes in pipe, etc.). Btw, running the codes gave nothing besides the usual ACT and knock sensor problems (codes 24 & 25). Thanks for any help!

 

[Rob94]

Sounds like you are experiencing a misfiring cylinder. The exhaust system does not produce sound. It simply transfers it from the engine. When is the last time you changed you plugs? Any oil in plug wells? You need to do a little investigating to find the cause.

 

[revhardSHO]

do a cylinder balance test on your motor...that will tell you if your draggin some pistons. I doubt it though, since you say it seems to be running properly.

Another thing you should check is the y-pipe-to-resonator connection. Mine completly blew apart during an "illegal street race" and the noise level went through the roof, alot more viberation too.

good luck

 

[sdpatt]

That sounds like a misfire. As said before, try the cylinder balance test. Did you replace the plugs and wires and with what kind? Check the bolting to the intake and the ground strap to the back, passenger side upper intake bracket bolt.

 

[Modemagic]

Rob94, he changed his plugs and cleaned out the oil and stuff either yesterday or the day before, during his 60k! I'm thinking a ways back when I had some exhaust troubles on a cavalier I have. I jacked the car up in the air, had a buddy stick a board over the exhaust tip while I was under the car. Once he did that, I saw the exhaust leak instanly dumping out of the holes. Just something to think about Pat.

 

[ScotSHO]

sdpatt:
Check the bolting to the intake and the ground strap to the back, passenger side upper intake bracket bolt.

On that note, maybe that blue aftermarket ground cable we removed was the motor to body ground? I looked on my 95 and there is a ground strap from the body to the back of the motor. Try replacing that to see if it makes a difference. I doubt it's the cats getting plugged.

Scot

 

[rendyx]

Scot Hewitt - 95 mtx:

sdpatt:
Check the bolting to the intake and the ground strap to the back, passenger side upper intake bracket bolt.

On that note, maybe that blue aftermarket ground cable we removed was the motor to body ground? I looked on my 95 and there is a ground strap from the body to the back of the motor. Try replacing that to see if it makes a difference. I doubt it's the cats getting plugged.

Scot

I'll bet that's the cause! I just thought of that, and I wonder if it did serve a purpose, maybe we were wrong about it being some stereo thingy. I'm gonna try that out tomorrow. Thanks guys!

And the cylinder test passed fine, so I wonder if it is the strap, and if it is causing any sort of random misfires.

The blue strap was found when Scot and I did the upper 60k. It appeared related to aftermarket stereo stuff, or some sort of ground problem (probably the latter in this case). And the plugs are AGSP32PP, wires are WR-4033. Plugs gapped to .044", and dielectric compound on all connections.

<small>[ February 16, 2003, 11:08 PM: Message edited by: rendyx ]</small>

 

[rendyx]

That seemed to do the trick, at least right now! It now sounds about the same out of the exhaust as it did before.

I'm still concerned that something may be happening with the grounds, so I'll be doing some further investgation. I suspect checking the resistance between the engine and the negative battery terminal would help. I'll keep you posted when I do this step.

Any other reasons the car may have a misfiring issue, which perhaps a previous owner tried to solve by adding more ground straps?

Another though, would engine degreaser leave an insulating film on the manifold brackets? I know if leaves something behind, but I didn't think it would cause poor conductivity for a ground.

<small>[ February 17, 2003, 02:14 PM: Message edited by: rendyx ]</small>