What is causing the engine on my 01 chevy cavalier to lope

Question edited for clarity.
Question moved to model category..

Jeff, our professional automotive electronics technician provides a great answer.

Jeff Armer
Dec 22, 2023
Ignition control module going bad could cause this. Test for spark when it happens, you know how to do that? Pull a spark plug wire an hold a screw driver in the end an close to engine ground, have someone crank the engine.

You should see a blue or weak white spark, or do you see nothing?
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Since it is an 01. First thing is to do a compression test for the cylinders. Look at the plugs also. Have the codes checked. Even if the light is not on.

Engine misfire. check engine light on ? Have you ever replace spark plugs ?

it is an 01 cavalier.

you PCM has spot a problem in the engine control system.you have bad sensor or EVAP leak or cylinder misfire.any auto parts store will code scan vechicle see what cause check engine light to flash on.they will code scan vechicle free go by auto zone.

Yes.
The cat could restrict the exhaust flow and cause the engine to run hot.
You would also notice a reduction in power and the check engine light would probably be on.

Check for a light in the dash that says SECURITY when it fails to start. GM has had problems with their antitheft systems for a long time. When these systems fail, they misinterpret the failure as an attempt to steak the vehicle, thus causing the system to turn off the starter. Read about it and find solutions on this link.

http://vatspasslockpasskeysecurityhelp.yolasite.com/

ENGINE LOPING CAUSED BY.LEAKING BY VACUUM LEAKS AT THE INTAKE MANIFOLD.CHECK ALL BOLTS ON THE INTAKE MANIFOLD TO MAKE SURE THEY TIGHT.YOU COULD HAVE LEAKING EGR VALVE OR PLUGGED PVC VALVE.DO A COMPRESSION TEST TO CHECK FOR LEAKING HEAD GASKET.DO A FUEL PUMP TEST CHECK FUEL PRESSURE.IT SHOULD BE 35 - 45 PSI.IF FUEL FILTER HAS NOT BEEN REPLACED.REPLACE IT FIRST IF FUEL PRESSURE TO LOW.DIRTY FUEL INJECTORS WILL CAUSE LOPING.TIMING CHAIN WORN.IGNITION TIMING OFF AND WORN LEAKING VALVES.AND WORN CAMSHAFT LOBES.ALL ABOVE WILL CAUSE ENGINE LOPING OR SHAKING.

So did you do all this to fix the loping or the loping came after the repairs? you have a 4cyl or v6??? Find someone with a scanner to check the PIDS.(scanner data)

try cleaning your idle control valve, make sure you dont have any codes in your computer, if you do address those codesl