What is this?

[knockknock]

3100 V6 ('99 lumina)

Please excuse my auto-tard self, but what is this 5-pin thinger right on the coil pack? Photo attached.

For some reason it dramatically reduces the knock in the mornings or at any time of day if it's disconnected. Granted it cruises like shit (stumbles a little) but it dead silent when cold. When it's connected it runs fine but sounds like shit. Wires are too messy to trace, guessing it might go into one of the relays but who knows, I'm hoping someone here might know offhand or has a wiring diagram and would let me know

(sorry for crappy cellphone pics)

[bszopi]

Umm... I'd keep that plugged in if I were you.



That connector is the connection between the ICM and the ECM. Withou that plugged in, the ICM is controlling the spark, NOT the ECM. And that is not a good thing.

[86euro]

I didn't think the car would even run with that unplugged.

[Guest]

Your car runs without that plugged in?

The coils will be reverting to static timing, based solely on input from the crank trigger. I know the car will run with one or two wires disconnected, but all of that plug disconnected? I'll have to try that.

[Superdave]

Your car runs without that plugged in?

The coils will be reverting to static timing, based solely on input from the crank trigger. I know the car will run with one or two wires disconnected, but all of that plug disconnected? I'll have to try that.

should be 0 degrees advanced.. i bet that's why thers no knock..


/me tries it too...

[3400-95-Modified]

Now how do you know it reduces knock... are you scanning? or do you mean your hearing knock you can physically hear and it removes that?

If you can hear knock then you have big problems elsewhere.

[knockknock]

Now how do you know it reduces knock... are you scanning? or do you mean your hearing knock you can physically hear and it removes that?

If you can hear knock then you have big problems elsewhere.

Knock / slap / tick / etc. are terms thrown around loosely by the uninformed such as myself. Don't get me wrong--I have that infamous piston slap ticking in full force and can be physically heard under load or at idle for a short time. My car also has another devilish nose that is more than a slap or tick but it's not a true knock such as detonation and is nowhere near a bearing or rod knock. Whatever this hollow echoing-knocking noise is, it's gone with the connection removed (and I'm left with just the light piston ticking) but if connected I'm greeted with a marching band when I drive for the first quarter mile.

I was just curious as to what the connector did (or didn't do) is all. not trying to figure out what the noise really may be--without tearing it down (don't care that much as i said just curiosity) it's been loosely accepted (by the fine members of this forum, other GM forums and my mechanic himself) as just a bad case of piston slap or a bad wrist pin (although the "knock" only happens when goosing the throttle and not on deceleration). the car has been doing it since the first winter i've had it and it hasn't gotten any worse or better. it did develop out of nowhere during winter 2005 and hasn't gone away last summer or this one.

[SHOoff]

Curious as I read that post and think of things to ask of the very knowledgeable here.

With that plug unhooked and the PCM not seeing any engine speed, or position, what's going to happen to the injection cycle? If the engine is still running and the the ICM isnt showing anything to the PCM, wouldn't that mean that the injectors are left open? Which may explain the absence of the ticking sound?

And the injectors at 100% when the engine doesnt need it (like cruise) would explain it running rough and stumbling really bad.

[Mr.H.O]

I beleive injector pulse width changes considerably but the PCM/ICM wont full field the injectors though.

Is there any possibility that you're experiencing a pre ignition pinging possibly related to your EGR system? Have you had and Emission test done recently? What were your nox, HC and CO readings like?

[bszopi]

The injectors shouldn't goto 100% all the time. They will go to a "fail-safe" mode that is factory programmed into the PCM. The ICM is also now in "fail-safe" mode and controlling spark independent of the PCM.

[Juglenaut]

The ECM would rely on the Mem-Cal for stored information on recall to limp-on mode, truely most cars would run like crap with the connector unplugged. The ECM tracks little info bits over the engine milestones and is able to block learn the fire of the injectors and fall back to batch pulse according to recalled pulse per rpm curve and A/F.

Something either fell out of time mechanical or software or the engine has a mechanical problem that needs to be addressed.

[rvbilly]

Use This

Hi ,or you could eliminate the injectors and put one of these in ,LOL LOL