Just as an FYI to everyone who may have this problem in the future, I wanted to detail my adventures over the weekend with my 1995 Neon.

Starting last week (3/6/11) I began hearing a strange noise everytime I really wanted to get on it and accelerate. It sounded similiar to the constant shhhhhhh sound when it is raining and the tires are kicking up a good spray. I also noticed that when it was cold, it just did not want to get going as easily from dead stop in 1st gear without having to give it more juice then normal.

Also, I had changed the oil and filter not long ago, and by the time I had put 2K miles on it since that time, I had to put 4 quarts of oil into it. That was really strange and caused me to look high and low for oil leaks (none found). I began to think that maybe I had lost some compression/etc. so I did a comp. check - all OK there too.

Then on Thursday of last week, on my way into work, I heard a loud pop and then every single time I added more power by pressing the accelerator, I heard the sound, even reving some at idle. I also noticed a loss of power. On my way home, I was afraid I would not make it home. It would idle, but any acceleration caused the car to buck, and sputter, and moan pitifully trying to go. I had a 1/2 tank of gas and it ran down to 1/4 just going 26 miles from work to home!

About a month ago, I got an EGR error code that cleared itself out, so I thought that maybe it had gone completely bad (no error codes at all however). I checked vacuum lines and EGR and did not find a visible leak, but I did hear an exhaust leak coming from the manifold. So I took off the airbox and sure enough, the doughnut gasket had pieces showing, so I thought that it was the source of the sound problem - and it was, but not the real underlying problem.

When I took the pipe off, the gasket was completely blown out! So I fixed it by putting on a new one, but then the car would not even back out of my driveway it was so pitiful! No power, would not idle, giving all kinds of error codes including misfires and MAP sensor errors. I briefly thought I had majorly screwed something up! I checked the plugs just in case I had damaged one when doing the compression check, and they were completely carbon'd up (I had just cleaned each of them when I pulled them for the compression check earlier).

I then began to suspect that I had a plugged cat and/or muffler. So, I took the pipe off, fired it up, and it ran like a champ! Loud as hell, but great! I probably pissed off about 20 neighbors late Sunday afternoon by driving it around the neighborhood, but I was happy that it wasn't worse.

I just don't have the tools to work on an exhaust system, nor did any local parts store have a cat in stock, so Monday morning, I took it to my local exhaust shop and they fixed me right up - fairly cheaply too for just over $250 (including labor, parts, and taxes). The cheapest OE fit cat I found online without shipping was $130. I had told the guy that I did not want any future troubles, so go ahead and replace the muffler too, but this guy was so helpful and honest that he told me that a) my muffler was fine, and b) would last longer then anything he had in stock and recommended I not replace it! I will go there as often as I need any exhaust work done!

Now the car runs quieter and smoother then EVER before. It easily accelerates, shifts cleaner even from stop. I notice that it does not take as much pedal to cruise at 60 as it did before, so I bet my gas mileage is going to get much better - and I was averaging 34mpg before this all happened. Oh, the car has 176K miles and the cat was the OEM original.

Now I am going to keep an eye on my oil situation, but I am hoping that since the car was having to work so hard to breathe and the back pressure of not being able to properly exhaust is the reason I was burning so much oil so quickly - but that remains to be seen.

 

I had a very similiar incident about 2 years ago with a clogged cat. I got more of a rattle noise though. Had the cat replaced and all was good. I still think I have some debris trapped in the muffler but it still runs good and I averaged about 35mpg on the freeway.

 

omg i wish i would have found this sooner.
I bought me a LEMON! lol its a 1998 neon R/T DOHC 5spd.

And ive done nothing but stick money into it. (kids, dont buy from indian reservations. they don't know the definition of maintainance or care care)

$2,200 later in parts alone, all 4 wheel bearings, platnium plugs and premium wires, new coil pack, all 4 struts, a drive axle, fuel pump and filter, power steering pump, timing belt (might as ****ing well change that too) numberous evap system leaks and vacuum repairs..

And it still didnt run worth a hell. I got it running, but after i ran a full can of seafoam through the fuel, and a can of seafoam spray through the throttlebody and intake, it got worse. I finally got mad and cut a hole in the bottom of the cat and the difference was unbelieveable.

Runs like a champ. Have yet to replace it, but im more worried about the grinding noise still coming from the tranny. x_x

 

I'm glad to hear that you found your problem. As for mine, the gas mileage jumped 3mpg and I have yet to burn a quart of oil. Having a plugged cat (or even partially plugged) is awful because there is no warning, no error codes and unless you have over 100K miles, no one even thinks about the cat.