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Question about mufflers and stalling

Hi there. I have a 2000 Cavalier that I bought from my uncle about 6 months ago. It ran fine until about 6 weeks ago, when I started noticing a noise coming from my muffler at low RPM. I thought it sounded like a rattle, but was unable to find anything loose. I assumed (in my infinite auto repair knowledge) that if there were a hole in the muffler, the noise would be constant. A few days later, the car started stalling at stoplights or when I was slowing to very low speeds. The problem is not constant, some days it is fine. I saw no visible damage to the muffler or exhaust system near the rear of the vehicle. The last thing that popped up is a slight hesitation when I press the gas pedal. The RPMs drop when I start to press it, but as I press it farther, the engine jumps back to life. The car always starts fine right after it stalls, as well. Do you think all these issues could be due to one bad muffler? Thanks for any thoughts.

No, they are not likely to be related to a bad muffler–if you even have a bad muffler. The noise that you hear at low RPMs could well be just a loose heat shield on the exhaust system, which is merely annoying.

As to the cause of your driveability problems–Did your uncle provide you with maintenance records for the car? If not, then unfortunately you have to assume that no maintenance has been done, and start from that point. As an example, if the car has ~90k on the odometer, have the 90k maintenance–as specified in the Owner’s Manual–performed.

If the car is overdue for spark plugs, fuel filter, air filter, transmission fluid change, coolant change, etc. you want to replace all of those items before trying to analyze the reasons for the driveability problem. With any luck, it just needs to be brought up to date with maintenance.

Thanks for the ideas. My uncle gave me what he had, which amounted to what only he had done to the car. (new tires, replaced a leaking oil hose). He did not drive it much for the year he owned it. He got it from my grandmother, who owned it for several years. While she had it it was maintained well, but she lost all records for the vehicle. The car only had 60 K on the odometer when I got it. Before my grandma, one person owned the car, and before that person, it was a rental car. I didn’t know about that until after I bought it, and my uncle gave me the carfaqs report he had done on it. The rental thing made me nervous because of what I had always heard about rental cars, but it seemed to run fine the first 4 1/2 months I had it.
I’ll have the basic tune up steps you mentioned done, and see if that solves the problem. I should have done that right away, I suppose. Thanks again.

While I agree with VDC that they are not likely related to a bad muffler, they could be. The muffler contains metal baffles inside that should they deteriorate and come loose can cause both noise replicating a hole and intermittant blockage of the exhaust system resulting in power loss and/or stalling. I took a system (one-piece welded intermediate pipe, muffler and tailpipe) off once and could shake it and hear the loose piece(s) rattling inside. The symptoms were the same as yours.

I Agree. Also, The Catalyst In The Convertor Can Break Loose.

I wouldn’t think it is as likely that the catalyst would plug up the exhaust the way a faulty muffler or resonator would. With the car parked and engine off, try kicking the tailpipe back and forth a couple of times. Usually you can hear a rattle if that is the source of the problem.

Well, I guess that it is possible that a blockage in the muffler or the catalytic converter could be the source of the problem, but since the OP stated that the problem seems to go away at higher RPMs, I discounted that possibility. Wouldn’t a blockage in the exhaust system get worse at higher RPMs?

OP–In addition to the basic maintenance, add a muffler and converter check to your list, just in case!

I was Thinking The Same Thing, But What About Something That Moves Under Higher Pressure?

The “muffler noise” thing may be a red herring.

If the check engine light is on, many (some?) auto parts stores will read the codes for you, for free. If any, bring the codes here for advice.
When you change the engine coolant (“anti-freeze”), change the upper and lower radiator hoses. Then, later, maybe next summer, one won’t burst and leave you stranded.

I thought of that, CSA, but that doesn’t usually make a noise like an exhaust leak.