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Vibration ! shudder ! popping!

OK, i’m gonna be as specific as can be (considering I’m not a mechanic…)

I got in my car, started it up with no problems, no warning lights, put it in gear and drove 5 miles at 50-55mph. It was purring like a kitten, shifted smooth (5 speed manual, 1996 Cavalier Z-24, 2.4 liter, dual exhaust, 72,000 miles). I came to a stop sign, facing upward about 10 degrees. (PS: I’m an expert at smooth clutching, even on inclines; I’ve driven mostly manuals for 40 plus years) Then I put it into first and, all of a sudden, OUTTANOWHERE !!! BOOMCHICKABOOMCHICKA, ETCETCETC…it was shaking like a banshee !!! I limped in the 3 lowest gears about 1000 feet to a stop. I looked at the temperature gauge. Normal. No warning lights. Then I shut it off. 6 hours later, before I cranked it, I checked the oil level. OK. No oil in the cooling fluid. OK. Then I cranked it in neutral, and drove it 150 feet into a Sears repair facility. (I work in the main building.) I left it running 5 minutes while I got a mechanic. He popped the hood and the whole engine was REALLY shaking in neutral. He suggested a vacuum leak, loose electrical connection, or bad plug. (but why would these things happen SO FAST with no warning…from smooth running to bonkers in a flash?)

He suggested I take the slow route back home, because he was closing for the night. Which I did. Here’s what happened on the way home. Shaking and sputtering. Shifting from first to second to third was smooth for the clutch (hydraulic) but the engine kept wanting to cut out, the higher the gear, and I had to goose the gas, just to stay turned on. When I went downhill, it did go into 4th gear, but still shuddered, but not as bad as in the lowest 3 gears. When I came to level ground or going slightly uphill, the shuddering was worse, and I had to start all over from first gear again. It sounded like misfiring muffler or exhaust manifold leak sounds: pop pop pop…and loud. Even in neutral. But the temp gauge was dead on. And still no warning lights. Finally I parked it in my lot, and shut off the engine. I popped the hood, and noticed smoke coming from the rear of the block. AND I smelled clutch burning. Could a vacuum leak spill motor oil onto a hot block? A gasket? If it’s the clutch, why would a separate mechanical system cause the shuddering and popping? Hmmmmm…this is one for the books. I have been too busy to go out and start it up again, which I will do tomorrow. I will check all fluids again, including the hydraulic transaxle (clear fluid). And I will confirm the color of the smoke. Any brave souls out there with a yen to point me in the right diagnostic direction? THANX !!!

a failed timing chain comes to mind. but that would be highly unlikely at this mileage. stop driving it. you may turn this from a minor repair to a total

Your first step is pulling the codes, followed by a number of diagnostic steps.
It oould be something as simple as a failed plug wire, failed CPS, failing fuel pump, etc. and yes, these things can appear suddenly.

At this point there is no way to make much of a guess about the problem because it could be one or more of a hundred things.

One quick check. Look at each spark plug. Are they all screwed in tight?

I believe that this engine has a coil pack with each of 2 coils firing 2 cylinders. If one of these fails, becomes disconnected, or the igniter output transistor for that coil quits, the engine will run on the other two cylinders but very poorly. The dead cylinders will be dumping a burnable mixture into the exhaust which will cause the popping and will overheat the catalytic converter and exhaust manifold burning off any accumulated oil. This type of failure does not give any warning, i.e. one minute everything is fine and the next it is barely able to drive the car. If you have an induction timing light, connect the probe to each plug wire to see if all are firing.

Hope that helps you in your troubleshooting.

I agree. Step 1 is to attach a timing light and see if each plug is firing. If you find that each plug is firing, I would suspect the fuel pump or stuck EGR valve.

It does not feel like a vaccuum leak to me. These newer fuel injected cars would compensate the fuel mixture. It wouldn’t run perfect, but probably better than it is.

Check your motor mount’s !!!