STALLING Chevrolet Aveo 1.2 20122 A12XER

STALLING Chevrolet Aveo 1.2 20122 A12XER
Got an interesting case and could use some info: It's a 2011/12 Chevrolet Aveo, 1.2 A12XER engine. Car starts and runs fine, then intermittently cuts out. At that moment there is pulse to the ignition block (a module), there is good feed , good grnd and no change in the grey/black wire (going to ecu but no idea what it does). Still my amps drop and disappear so the spark is gone. Customer already changed plugs and wires before car came to me but as it certainly seemed coil I changed it for another brand (they placed NGK, I used Hella) and after replacing NGK plugs, changed them for bosch (torqued OK). No change. Made several images and wondering why the coils are cutting out.
Lot of times no restart till after some time letting it sit. So either electric stuck or problem with heat I assume. It seemed to me idle went up a bit before stalling but don't see it in injection pulse so might be mechanical issue causing extra heat? Already had car running on battery instead of alternator to sample an a/c overload out of the situation (was a bit high at times). No change.
Timing have no good reference for this car, though with an Opel , also A12XER there is no difference vvt connected, taking in-/out vvt connectors off, it's not ok. Also seeing about 50 percent VVT adjustment on idle, which seems weird to me? Gas test tells me lambda works fine and trims are within 10% long  and short together (nothing special).  On stalling while scoping timing did not see obvious changes before stalling.  Still need to record live data MAP etc while stalling but since injection pulse don't change before stalling no big suprises to be expected. Connector coil checked visually and wiggled, no change in scope images but still on the cards.
Anybody any input on this and anybody has correct timing reference image on scope? Sorry for the long text - want to give as much info as possible.            

I don't have a diagram but if the ignition module (is it a separate module?) is getting pulses from the computer to fire the coils and you have no current ramps, you've caught the failure in action. Confirm good power and grounds and good connection between module and computer and call the ignition module.

It seemed to me idle went up a bit before stalling but don't see it in injection pulse so might be mechanical issue causing extra heat?

When you do manage to get it running again, unplug the module and see if it stalls like you describe.

I agree with jreardon on this. To me this sounds like a ignition control module failure but check power and ground of ICM and feeds to and from pcm to confirm.

Garage did that before bringing the car to me (not diagnosing it in deep but just as a trial) and as I came to the conclusion you did , I replaced it as well. Were it that simple , would it have been fixed in short terms already

wrote:

It seemed to me idle went up a bit before stalling but don't see it in injection pulse so might be mechanical issue causing extra heat?

When you do manage to get it running again, unplug the module and see if it stalls like you describe.

-- if I take connector off it will stall, no doubt, since the module is an overhead ignition coil for all 4 cylinders. But again; it's just the amperage (coil building field) that is gone, not the 4 pulses to time/signal them and also not the feed or the ground. It certainly looks like coilpack/module (1 item) but after 2 new ones and new sets of plugs I don't believe in such a thing (different brands also). Right now only 1 thing is most logic and that is a connector, even though it's not visibly and not to be replicated so far (it's the only thing between measured / scoped values and the failing coilpack/module). Only other thing might be engine heat inflecting on the coilpack/module?

 

Hmm might be worth running a thermal imager over the engine compartment to see if something is going on inside a wire then. Did you load test the wiring with a 4amp bulb?

With the new info given I would look more towards pcm given that. Possibly a solder joint or a loose pin at icm. 

took scope images right at the coil, so I would be certain to see or power, ground, or pulses/signals would be lost on their way , they are solid as a rock until after the coilpack stops working. Please let me know the extra function of testing with a bulb. The car runs fine and does strain all above during that . Don't get me wrong, I really appreciate the ideas you ring up here!

The thermal check is not a bad idea, but even better on the coilpack self to see or 1 of the coils (4 in them) is out of league. Had a test prepared on paper already to see wether or not it fails on the same signal/pulse (cylinder) so that would be an indication also

With a (4 amp turn signal bulb) test bulb and connector hook one end to ground and connect the other end backprobed to one end of disconnected harness (ICM connector) and at the other end of disconnected harness (pcm connector) backprobe a fused wire supplying 12 volts. If bulb lights brightly ie same as if it was hooked up to battery then your wire is good. But also wiggle harness around the full length to see if there is a flicker or loss of illumination. This is a sign of a break in the wire internally.

Hope this helps you

I am aware of the test in this case it does not bring that much extra. The power and ground are tested with scope at the connector of the coil. If a wire issue would be the cultprit, we would see a drop in voltage or rise in voltage (grnd) when the issue occures... it does not. It is already stressed, by way more amps than 4 of the bulb by the coil.

Only possible extra it could do is testing the harnass but that is only 1 moment test, it won't stress with the heat of the coil backfeeding in it the way the coil does. So even though it does give a testing solution indeed, it's not solid?
 

SOLUTION: as other options were rooted out and a test with the connector still presented no issues (with the bulb, checking amps etc) still welded another connector into place and that solved it. The only thing that might have given a clue was that at the last test just before cutting off the connector I stressed it gently again and noticed a SLIGHT drop in amperage for maybe 2 ignition events... no more. Even when not restarting, a test of the connector with loaded circuit etc revealed nothing... It's one of those little mysteries that I hate since you should always be able to prove what the issue was (kind of did by but not like I want)