Original owner of a 2005 Cobalt LS with an engine issue that's difficult to replicate and diagnose.
Everything generally runs fine, no leaks, performs well, always starts up smoothly, all mechanically good, maintained throughout its life primarily at the servicing GM dealer. Never been in a collision, flood, modified, etc. Kept very clean.
A few months ago, the car began exhibiting intermittent stalling and nearly-stalling incidents where it seems to "recover" itself quickly enough to continue running. Never struggles, just dies. Doesn't matter whether you're idling or cruising, highway or city driving. The problem is, there's no DTC generated, not even anything pending according to my Autel AL319 reader. Curiously, the runtime since engine start parameter resets whenever I experience one of the almost-stall events, even though the engine doesn't fully quit running.
These hiccups occur maybe once every few times the car is driven, without any common conditions. The check engine light comes on as soon as it begins to stall, but goes off within one second, usually when the engine RPMs go back up to normal. It happens so fast that unless you're staring at the dash, or accelerating hard and feel the brief loss of power, it's barely noticed. If the engine does completely quit, it's immediate, as if the ignition had been abruptly shut off, and I can always restart it without difficulty, suggesting it's not misfiring. Ignition switch never comes out of the run position on its own.
First attempted remedy, I had the throttle body cleaned, but the problem persisted. Then, I checked the fuse boxes and everything seemed snug, no sign of contamination or anything blown/burnt. Had suspiciously similar ignition module problems
with a different (Ford) car I used to drive, so I tried replacing the ICM, but that didn't fix it, either.
Sure, something common like a corroded ground connection is possible (often a nightmare to locate) but I'm beginning to wonder if it's rooted in an electrical or fuel delivery fault. Should I try getting the fuel injection serviced? If the injectors are dirty and/or the fuel filter is slightly clogged, could these conditions cause random engine shutdowns without any codes, yet otherwise operate perfectly normal?
The odometer just hit 78000km (say, 48000 miles) so yes, it has very low mileage; gets used once or twice a week, lately... formerly used the vehicle to commute to work during its first six years or so.
I have online access to the chiltonlibrary.com database (mostly a replica of GMSi) and have not found any applicable tech bulletins.
Eight years ago, I had the TCM replaced at the stealership after the car suddenly acted like it was electrically possessed while running, but I've read numerous accounts that apparently it's a common problem.
Seeking help/suggestions from the audience...