Hi everyone, I'm new to the forums but not new to owning a cavalier. I got my first 2001 Cavalier z24 automatic (her name was Lilith) in February 2008 and after two wrecks totalled her, I bought another 2001 z24 automatic in April this year. I knew when I bought the second one (I named him Taco) that he had some massive issues, but I ignored it because I still have the mechanically sound, albeit ugly, Lilith in my driveway. There were a lot of parts in Lilith that were new or had been replaced in the year before, and I kept all of them and also stole parts like a hub assembly as needed to repair this car.

Anyway, that car took an insane amount of repairs to get into running order (I had to idle it in traffic on the way home so it didn't stall, if that gives you any idea). I've had small issues that I didn't bother to really fix - there appeared to be a vacuum leak in the HVAC system so the car woudl run rough when it was on but ran perfect with it off, I replaced the stock stereo with an aftermarket head unit and noticed it occasionally caused the headlights to dim, stupid little details, but the car was a dream for the past several months. I finally felt comfortable letting Lilith go to her junk yard grave a few weeks ago since Taco was being so wonderful. Then Saturday things went crazy. This is a long story, with a somewhat happy ending.

Saturday the car ran great as always until I parked at home for half an hour. When I went to leave, I got 2 miles down the road when the car started shaking like an overpowered V8 (I'd know, I own a supercharged 95 camaro too) and within a few seconds of the shaking, the Trac Off light came on and the engine threw a code for a random misfire. And at one point threw a secondary code for cylinder 3 misfire. I immediately replaced spark plugs and boots, no luck. Long story short, I ended up purchasing and installing - throttle position sensor, spark plugs, boots, iginition coils, ignition coil housing, ignition control module. I already had decently new cam and crankshaft position sensors. Nothing fixed it and it was getting worse. I tried using the practically new PCM from Lilith and both PCMs had the same codes, same issues. I ran through almost 10 gallons of gas in less than 50 miles but I couldn't smell fuel anywhere.

When I checked my fuel injectors after all of the above, I found cylinders 3 and 4 stuck wide open, cylinders 1 and 2 were random. So I replaced all 4, still nothing. It was then that my friend noticed where the shaking was originating - my catalytic converter and the cat was glowing RED hot behind it. When we backed off the catback, we found the cat was clogged, almost not allowing any air flow, and the internal honeycomb was crumbling. So we hollowed it. Given the late hour, we partially hollowed it, called it a night, agreed to continue next evening after work. Drove to work (46 mile round trip) yesterday like that and noticed a huge improvement but still random misfire and Trac Off light and shaking and terrible MPG.

We finished hollowing the cat last night and c-clamped on some straight pipe and used spacers on the rear o2 sensor. While that stopped the shaking completely, the random misfire and trac off light stayed on. We checked the spark plug gap, everything, no improvements. Until actually I think we stumbled on someone's post on here and discovered that we should check the wheel speed sensors. They were terribly dirty and cleaning them did fix the entire issue. I guess in these cars if that sensor doesn't signal right, it triggers traction control which then closes off two cylinders in order to regain control? Suddenly, it made sense. That was one hell of a chain reaction problem!

Anyway, so the car has run perfectly since then. I need to re-examine my fuel consumption but it is definitely not wasting gallons like it was when this started. And no codes so far from the catalytic converter. Actually, aside from sounding like a pissed off weed whacker, the car seems to really like being without a cat. And oddly enough, the HVAC system leak I thought I had seems to be gone.

So I now have this question. Will running without a catalytic converter affect my car in any way (good or bad) besides failing emissions? I just ran through almost $1,000 in parts in 3 days, I don't have the money to replace the catalytic converter yet, but I don't want to damage my car either. Emissions don't matter - I just passed a week before this crap happened. I know I have to replace it before I do emissions, I just need more time to get more money.

interesting story, i know when my z threw a coil set it dumped fuel and ruined a cat. universal ones from summit work well if you get them welded in.

Thanks for posting. I'll keep that in mind.

I don't know but I think the only thing downwind of the cat is an oxygen sensor and the muffler. I don't think a missing cat would harm them. Not sure.