Vx - Does knock detection cause spark misfire?

[Charlescrown]

I'm not sure if you blew air thru the correct hose. It's the hose that comes off the fuel pressure reg back to the tank. The hole size inside the tank is only abt 1.5mm and a tiny bit of dirt can block it. If you can connect your fuel pressure gauge between the regulator and the return line and see what reading you get. There should only be a low reading. If it's as high as the pressure on the supply side it's blocked. A simpler way is the disconnect the retrun hose and rout it into a container. If the car then idles properly then check for a blockage. Be careful as there will be about 2L a minute flowing in the return line so you'll need a big container if you run it too long.

[JohnDee68]

Thanks Charlescrown.
Yes, that was one of the lines i blew threw. At the time I had the tank out and of course, forgot it still had fuel sitting in that line and it mad a mess under the car. I also checked the other lines while apart and there which all blew through as would be expected.

An update on today's findings:

I did a fuel pressure line test, it came up within specs around 40psi. I tried to do a injector bleed using my (china) injector pulse tool. The new injectors wouldn't operate while there was more than about 25psi in the fuel rail. I investigated further and found that even off the car and fuel rail they wouldn't operate using my testing tool. I first suspected the tool was at fault, so tried it on the previous injectors i had replaced for the new ones. It worked fine. So, that didn't seem right to me that all 6 new genuine injectors were failing to operate like the old ones on the tool. I checked them again and they still were hit and miss as to even operating. I measured the injector resistances and they were ALL 9.8 ohms. Which according to my manual, that is a failing to their operational range needing to be 11.8-12.8ohm. The old ones measured close to 12 ohms.

I wasn't sure that such a little drop of resistance would cause the issues of the tool not activating the injectors. So I decided the best way would be to fit all the old injectors in to the car and see what happens to the fuel trims. After fitting the 6 old injectors back in to the car. It resolved the major negative fuel trims instantly as they came back around the zero. Though running rough, hiccups and non smooth throttle, the engine fuel trims were reasonably ok considering the old injectors being used. The previous fault of O2 sensors not always staying in Ready state returned as did the closed loop mode not sustaining as it did with the new injectors fitted. But the fuel trims were around the 0, give and take +-8%. So I am hoping at least my fuel economy might be more bearable for a few days while i work out what to do about the injectors.

So, I am now questioning if the injectors resistance of the new injectors really is a fault in the injectors as per the Gregorys service manual or is it just possibly that presumably at least 2 or more failed injectors are able to be professionally cleaned and be able to return to as good as new again?

Also, why do they function electrically fine on the car, but not on the bench via my china tool? Could it be the tool needs a minimum 12 ohm load to actually operate or just not able to output more than 1000mA ?

Anyone know of anyone in SA who might be able to assist me in getting my injectors looked at and tested as I cant afford to purchase a new set at this stage.

Thanks guys.

[MudDuck514]

SNIP

Also, why do they function electrically fine on the car, but not on the bench via my china tool? Could it be the tool needs a minimum 12 ohm load to actually operate or just not able to output more than 1000mA ?

Thanks guys.

With the lower resistance, the injectors WILL try to draw more current. I would suspect that the tool is incapable of supplying the needed current to operate the injector.

Mike

[JohnDee68]

With the lower resistance, the injectors WILL try to draw more current. I would suspect that the tool is incapable of supplying the needed current to operate the injector.

Mike

Thanks Mike, I was thinking that may be the case here.
I also presume that when the service manual suggests a resistance check. It is to basically check for the extremes of either short or open circuit in an injector to determine if it needs replacement.

[immortality]

Sounds like counterfeit injectors. Unfortunately if that is the case then the bin is the only appropriate place for them.

[JohnDee68]

Sounds like counterfeit injectors. Unfortunately if that is the case then the bin is the only appropriate place for them.

I think it is unlikely, this time. If they are they are very well done. But I can't confirm it.

I want to try and test them myself on the bench just to see what ones if not all have actually faulted. As I'd like to use them if they end up being better than my older mix of injectors. I'd be interested in what they actually were doing to cause the excessive negative fuel trims so equally even on both banks.

I'll keep you all posted to my findings. Tomorrow I need to take the car for a 500km ride. So am hoping the old injectors hold up ok for the trip.

I've ordered a cheap cleaner tool which just fits on a can of carb cleaner. But that'll be nearly 2 weeks away.

[MudDuck514]

SNIP

I've ordered a cheap cleaner tool which just fits on a can of carb cleaner. But that'll be nearly 2 weeks away.

I cleaned the injectors on my 2.4l LD9 Twincam by connecting 2 leads to the injector, connecting one lead to the battery negative terminal and spraying cleaner into a hose attached to the injector while tapping the positive lead on the battery, REALLY quickly.
Did all 4 and the car has been running fine for 3+ years now.

Mike

If you are worried, and have access to them, a 1,000 Ohm resistor in series should limit current to a safe level.

[JohnDee68]

Thanks for that feedback Mike.

I will give that a go once the tool arrives. The cheap china tool is just the same sort of method. It sits on the can of cleaner (carby cleaner) and you run it through the injectors. I am hoping that when it arrives within two weeks, I will be able to at least get 6 working injectors out of 18 (plus another crappy 5 China made ones) I now have around the place.

Am taking the car for a long run today. I will see how the spark plugs look after. They should let me know of what sort of condition the current (old set) injectors are doing?

If I had the money, I would likely buy one of those cheapish injector cleaner tools. The Autool ones which are for about $500 upwards. But I can't afford it at this point.

[JohnDee68]

Hi guys, as this is an ongoing diagnosis issue I thought best to keep it all on this posting rather than start a new one (unless directed otherwise).

I am experiencing weird issues while trying to diagnose this car. (I will update full details a little later, just need to finally get it resolved as soon as I possibly can and no rain outside).

I am wondering if someone who has access to a Vx 2002 commodore 3800 v6 stock system AND the Advanced Engine Diagnostics Software by Envyous Systems. ( I realise I am asking a lot).

I just need some confirmation that another similar car isn't getting the same results as I am, because if they are I am chasing a non-fault (smells and runs Rich and rough). (All with respect to the software - If it does read correctly, then I need to again go over my well worn path of diagnosis) I just need to confirm it is actually giving me correct readings of which I am using to diagnose the fault.
As the values I am getting back don't make sense for my current understandings.

I notice my Injector Pulse Time goes from around 1.6 to 2.0 at idle in both closed and open loop. However, while driving around 1700 rpm, the IPT can go upwards of 200-1000mS. Way too high according to my research online and I don't know why?

A snap shot of values at a given point in time from Advanced Engine Diagnostics Software: While driving on relatively flat road.
In Open Loop Mode !
Engine coolant Temp: 83degC
Vehicle Speed: 97kmph
Engine RPM: 1788rpm
Intake Air temperature: 20degC
MAF: 34G/s
Injector Pulse time: 512.82ms
LH O2: 13mV
RH O2: 27mV
STFT: 0%
LTFT: 12%
Air Fuel Ratio: 17
Knock Retard: 78.75
IAC steps: 82
Spark advance: 25deg
EGR Pintle Position: 95%
EGR Pintle Position Feedback: 213
EGR Pintle Desired Position: 95%
Canister Purge Duty Cycle: 41%

I have noticed (only today), while watching very closely in the log file, that I am now getting Knock and retard ignition timings (very briefly and only occasionally - never before). I wonder, could faulty Knock sensors cause these readings? I cant see how the IPT would be that high though regardless. If anything when a knock happens, the ITP should be less not higher in my logic.

Keep in mind I cant rule out 100% electrical wiring issues as well. I just haven't been able to find confirmation to prove it as a cause. This is also a work in progress to get my car running back to reasonable again. I have replaced too many (actually not faulty) parts already with no positive results.

Thoughts appreciated.

Regards
John.

[immortality]

Where did you get to with the dodgy injectors?

Looking at those numbers you're just cruising down the motorway in lean cruise mode.

The knock retard numbers don't make sense though.