V6 knock until CEL sets, may be “left bank knock sensor circuit malfunction” related.

[Rawrs]

Hey guys,

I’ve had this problem for a good couple of years now but it’s only now started to get worse. In this period of time I’ve done probably 70,000km.

Ok, so what started happening was the check engine light would set when accelerating. No apparent problem, it just sets. Had this checked. I can’t remember the actual trouble code itself, but it was for “left bank knock sensor circuit malfunction”. This didn’t have any apparent impact on the car so I left it on the back burner for a while. Admittedly longer than I should have. Now I have a new problem.

When accelerating under certain loads, the engine will start to knock or maybe ping quite loudly until either you let off, or the CEL sets. If you pin it, it will ping less. If/when the CEL sets, there will be a tiny, momentary pause, probably while the ECU retards the timing, and sets the light, at which point the engine shuts up and you can drive it around all day quite happily, although it will be a tad sluggish, probably because it’s running a standard ignition map, at least that’s what it feels like.

No misfire, no rough idle, starts first time, every time, with the exact same amount of cranks, and it will not knock on idle. BUT I found the CEL is often slightly easier to set when the engine is cold, but it won’t knock until it’s warmer. I’m thinking there might be something funny going on with the closed and open loop modes.

As I’ve said, I’ve had the problem in a minor fashion for a couple of years, but it’s now starting to become very worrisome. I’d like to know what it is and if there is anything I can do to avoid grenading the engine. I’m somewhat sceptical that a failed knock sensor could present in this way, but I honestly don’t know.

I’d love to have one of you Ecotec whisperers to chime in with your thoughts.

I’m also thinking about getting one of those ALDL cables that you shove into a laptop, but I’m wondering if you can get mode 6 data, or whatever the ALDL equivalent is, if there is one. I’d love for someone to come for a drive and actually have a look at this engine and see what is actually going on. Thankfully it takes all but 30 seconds of driving, and the problem seems to be extremely well defined, if odd and worrying. If it helps, I’m in Brisbane.

Cheers,
Rory

 

[Rawrs]

Hi all;

I'm sorry to bump, I'm sure there must be a rule against this, in which case, I apologize, and won't do it again!

But I'm completely lost as to what to do for my car. The only thing I can think of, is hooking up an ALDL cable and seeing if I can get something resembling mode 6 data, at least see if AFR plays a part, or if there might be a deceptive little part of problem causing all this, a vacuum leak from the currently badly leaking valve cover gaskets, anything.

Any ideas at all? It's getting to the point where I'm starting to worry. Once the CEL sets, it's fine to drive it how you wish - it will not knock or make bad noises. But to set the CEL, takes specific actions to do, and doesn't always work. Before the CEL sets, even moderate acceleration causes the knocking. Letting off the throttle shuts it up, as does absolutely pinning it, sort of. It makes it sound less worse, for want of a better phrase, but not go away completely. Only the CEL setting makes it go away completely.

Any takers at all? Absolutely any ideas you could throw my way would be greatly appreciated.

Cheers,
Rory