Vx - Does knock detection cause spark misfire?

[Charlescrown]

It'll tell you that the circuit was working ok and then with a knock sesor out logging code will then tell you the limp home works. Then just reconnect it and erase the code and moove on with the diagnosis. That figue of the injectros delivering 50% more seems impossible it would run. 50% is a massive amount of extra fuel.

[JohnDee68]

It'll tell you that the circuit was working ok and then with a knock sesor out logging code will then tell you the limp home works. Then just reconnect it and erase the code and moove on with the diagnosis. That figue of the injectros delivering 50% more seems impossible it would run. 50% is a massive amount of extra fuel.

Thanks Charlestown for clarifying that reasoning. It makes sense now and is a good idea. I will do that.

That figure for the injectors was during bench testing in an injector machine. Over a 10min period they put through 85mL as compared to the current originals of 55mL. Sorry, it is 30mL difference and 54.5% change as per the calculator at https://www.omnicalculator.com/math/percentage-change. I know it sounds a lot, but fuel consumption was up near the 20+L/100km with them in which is nearly double what I am estimating currently on this last fill already. It ran like nothing i have ever driven before. It NEVER threw up any codes which amazed me though. Hence my confusion in this whole saga.

I will try that disconnecting of the sensors and see what happens. What is the symptoms of Limp mode in the commodore. I have never experienced it as far as I know.

At times going through the mountains in the eastern states it had a real bad drop in power and vibration/shuddering feel. Felt like i was driving over a road of consecutive speed humps up a mountain road. I couldn't stop or pull over due to no room, so had to continue upwards. Could only get to about 15-30 kmph up the hill or it would feel worse like it was going to explode the transmission. I put that down to transmission / Torque converter aged issues though at the time as it is also the original trans and torque converter.

Thanks for your time Charlestown, i do appreciate all suggestions and thoughts. I am determined to resolve this issue and have my car working like new again, someday.(I don't have a choice).

[Charlescrown]

Limp mode with that code will pull (Ithink) 10 degrees of timing so you will notice a drop in power plus the light on. Its just to confirm the circuit is operating and your program is not corrupted. Where did you get those injectors and were they the same colour as the original ones? Theres lots of rattling things that may trigger a knock sensor and going off the logs it's a lot of knock occuring. False triggers show up under strange conditions not like a real knock which will usually be under acceleration so if it's all over the place it may well be something loose. Check over the exhaust brackets their a common trigger.

[JohnDee68]

Ok, that makes sense about the limp mode. Though the knock tripping in the logs has shown retard degrees upwards at times of 28deg I've seen.
The knock reports in the logs seems to be mainly on acceleration. But unlike the old days when you could hear or even feel a knock. I can't feel anything or hear anything like that from the engine.
Unfortunately I didn't get to work on the car today. But in the next day or so I'll definitely do the knock sensor disconnection and see what happens.

About the injectors that put out more fuel than the current fitted genuine ones, is still in process of dispute while I'm trying to get my money spent on them back. But their confirmed by Bosch to be counterfeit injectors based on three main criteria.

Thanks again. I'll keep this thread updated as I progress.

[JohnDee68]

Ok, I have just taken a look in TunerPro, at the knock sensor settings area.

Any thoughts on this guys.

I see that the Cyl # knock sensor select areas have only the 2, 4 & 6 cylinders selected. Is this correct for the V6 ecotec engine ? It seems a bit strange. I would have thought that either ALL would be selected or just a minimum of 3 & 4 because they are opposing & centre cylinders.

[Charlescrown]

You can turn off the knock sensor in the earlier ECU's with ESC parrams but I don't know on your model.

[JohnDee68]

You can turn off the knock sensor in the earlier ECU's with ESC parrams but I don't know on your model.

Ok, it looks like my Pcm in tunerpro has the ability to turn of the Knock sensor learn mode. Also deselect what cylinders it can apply to. So I might try that first and see if the logs show them as off.
Was I'll today so didn't get to achieve what I had wanted on the car. Maybe tomorrow.

[JohnDee68]

Hi Guys, sorry it’s been a while without any updates. Life issues got in my way.

Anyway, here is an update of events and findings to get back up to date.

I managed to return the O2 sensors which were not quite responding as they should have. I then got genuine (yes confirmed genuine) Bosch O2 sensors at a fair cost and fitted them.
I still had what seemed like miss firing causing a slight roughness at idle. So I went back over the typical things, checking for any obvious issues or signs of failings. On removal of Spark Plug Cyl#5, I noticed some carbon around the outside of the plug.

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This turned out to be coming from the exhaust manifold gasket just above the plug. So I obviously checked the manifold bolts again for tightness. Believe it or not, all but one bolt on each of the manifolds were slightly lose. About 90-270 deg turns required to tighten back up. These weren't lose the other time I had checked them just around the time when immortality had his issue of similarity. (Thanks again immortality for mentioning that.) Unbelievable, but I am continuing to monitor these bolts. If they come lose again, I will lock tight them in next time. I am still working on repairing my home made smoker machine to test the system again fully.

So with the new O2 sensors fitted and the exhaust manifold tightened up. There is a noticeable improvement of fuel consumption. An estimate is around 13L/100km mixed driving. Just from a logical guess and gut feeling.

So I have been running further tests as it still had very poor performance when driving. TunerPro seemed to show a spark timing retardation in relation with knock detections. Not knowing if the original sensors are faulty and getting phantom readings, I thought I would disable the knock detection as a diagnosis method. The car had a noticeable feel of improvement in its performance without any audible knock that I could hear anyway. So I started looking at possible causes for the knock detections. I did enable the knock detection again, while also reducing the knock detection severity of spark timing retard. I have come to the conclusion that the knock is only happening when a lean mixture is happening. This occurs (according to TunerPro) under acceleration times mainly. As the car obviously self retards accordingly. I am talking <5 deg retarding before knock stops, so not major, I don't think. I am still unable to confirm if the original knock sensors are faulty, worn out or still working ok. But for now they seem to be adequate. The car seems more responsive and performing a lot better than it has for many years.

I have also been running in cruise mode as much as possible to hopefully self clean the cat in the exhaust (thanks again immortality). I cleaned the tailpipe end to help in monitoring its new carbon build ups. It is nowhere near as black, but more towards grey colour. Due to previously bad injectors.

Now to current day, I still have the (slight) knock detection under acceleration which I am trying to tune out. While I am also hoping to rebuild my smoke machine to do vacuum and exhaust leak testing soon. I am yet to do a actual fuel economy check as fuel is just ridiculously expensive her at the moment. But I will give you an update when that happens.

Looking at Knock.gif (51.97 KiB) Viewed 642 times

[immortality]

Fit a set of exhaust manifold gaskets, from the factory there are no gaskets and with thermal expansion and contraction without any give the bolts come loose which is why from the factory they have those half moon straps between each set of bolts. Once those are removed they will forever come loose, fit a set of gaskets and there is something that can handle a bit of expansion/compression and should help with the bolts coming loose problem.

[vlad01]

Would be nice if someone would repros of those locking plates, they are NLA and I only have one NOS set left stashed for the last big project. I try to save as many as I can when I do exhausts or go to the wreckers.

Wold just need to CAD up a design and get a shit ton laser cut from prob 24 gauge gal like the factory ones.