Car issues

[RedHeadedStranger]

Anyone around here know anything about cars? I have a 97 gmc 1500 and yesterday as I was driving it seemed to be louder than normal. As far as I know all the exhaust and pretty much everything else is stock, but it sounded almost like it was straight piped, definitely louder than before. The engine also started "skipping" for lack of a better word, maybe misfiring I guess, not really sure. There was a rattling sound in the exhaust, and I crawled underneath and looked around and that was coming from the catalytic converter. I assume the cat is shot, would that cause any if the other problems? Any help would be greatly appreciated.

 

[malador]

You might check to see if the converter is plugged.

 

[Tex]

Part of the 'honeycomb' of the cat probably broke loose and plugged up the exhaust-way. This will cause excessive back pressure and make your engine run rough.

 

[RedHeadedStranger]

Awesome, I'll look into that in the morning. Thanks y'all

 

[DirtyOldDuck]

If the engine sounds like it is straight-piped, you might also check to make sure there is no hole in the exhaust. Back pressure from a clogged cat can cause a break where the exhaust pipe connects to the exhaust manifold on the engine.

 

[dkwolf]

Also, if the cat is plugged, the downstream oxygen sensor isn't going to be getting the readings it expects, so it'll start messing with your air/fuel ratios to try and fix it. But the 'louder' comment perplexes me; when mine (gradually) plugged up, the truck got quieter. Granted, mine WAS straight-piped from the cats back.

 

[Misplaced_Canuck]

Could be a cracked exhaust manifold, happens a lot on Jeep Wranglers of the day. [Yes I know it's a GMC he's talking about]

MC

 

[Jacob_Marley]

If the engine sounds like it is straight-piped, you might also check to make sure there is no hole in the exhaust. Back pressure from a clogged cat can cause a break where the exhaust pipe connects to the exhaust manifold on the engine.

Take a 6 foot length of rigid tubing if you can find one ... an old PVC pipe works well, and with the vehical running put one end of the pipe to your ear and point/pass the other open end slowly along the length of the exhaust ... you will be able to note where the leak in the exhaust is when you come to it.

Don't forget to run it slowly past anything that has a seam or crimped seam on a flat or sheet portions of its structure.
The seams on things like mufflers, catalytic converters etc can blow out on an old vehical.

 

[RedHeadedStranger]

Double post

 

[RedHeadedStranger]

Thanks for all the suggestions, I'll probably start by replacing the cat since I know that's broken, and check all along the exhaust for leaks/holes and go from there. I'm hoping the engine running rough is just an effect of the cat going out, I'll just have to see I guess. Thanks again everybody

 

[BrewerBear]

Look at the exhaust where the left and right side join into one.