Easy and free fix for vz v6 engine miss (faulty ECU)

[mechanic]

Good lord... there is so much misinformation in this thread. It is plain misleading and wrong on so many levels.

 

[Fu Manchu]

Either the best pun ever, or you should be pointing out the misinformation and provide some reference or explanation of why and what the solution is.

 

[Fu Manchu]

So I performed the splice after 2 odd years of procrastinating and persisting with erratic performance. Always cylinder 2 misfire. 300 and 302 codes every time this happened.
I could manage the vehicle by backing off and or changing down to 3 when the going got tough and revving it out a bit. Then it felt like it would clear out somewhat and run smooth - just right on the edge of throwing the codes again. Mostly noticeable at idle and slowly adding load to the engine in top gear when converter is locked, towing, AC ect.
Then on the weekend it finally just stayed. Threw the codes and wouldn't go away. Rough idle all the time very erratic all pointing to cyl 2.
Performed the splice to cylinder 2 to cyl 1 and took a little while to clear out and begin running smoothly and idling smooth but definite improvements. But the powertrain error and engine light wont go away. I have cleared the code and it disappears but comes on next engine start. Has anyone had this after a splice or could it be another issue?
Also drove around for a bit with my diag tool connected to laptop and notice o2 sensors on each bank a little strange. I would have thought they would read fairly similar but bank 1 is reading around .83 volts and bank 2 less than .1 at idle. Pic attached if anyone has any ideas.
If anyone would like to see data of any other sensor to help diagnose (if you can be bothered) let me know.
Anyway apart from the powertrain light the car seems to be running heaps better thanks for the help so far.

Edit - have already changed the plugs and coils before doing the splice.

Get the cats checked out. You can do it but you will need an infrared thermometer.

Check pre and post cat temps.

A blocked or inefficient cat can cause misfires in severe cases, erratic performance in some circumstances, and affect the engine management system (eg. o2’s).

On a less extreme level, test the o2’s.
They do need replacing periodically.

If you start a new thread on o2’s, I will post some simple tests you can do yourself on Saturday when I’m home, or better still other helpful forum members might find the thread link to the test o2 topic.

 

[Fu Manchu]

In reference to 60HOM's diagnosis steps in 2013; Probably stupid question but i'm confused what is faulty here in this statement below? Would i need to replace the injector in this case? "If the miss moves then your coil pack is faulty, if it stays then and the spark plugs are good then its your inj which means your ecu has dropped out that inj due to a possible short from that coil pack.". Also, if possibly the coil pack has shorted then does that mean coil pack is faulty or or we talking about the wiring to it's plug?
Actually i have Cylinder 2 down and the ODB2 error is "P0202 Cylinder 2 - Injector Circuit Problem", troubleshooting it now.

I was getting the same fault with injector 1. There was no fault with the circuit. Once I replaced the cats (there’s a thread on my woes with the issue) all the faults, glitches, performance probs went away. Tests on the cats checked out ok, they weren’t.

 

[mechanic]

you should be pointing out the misinformation

Since when is driving two injectors off one signal a 'fix' for a problem? A temporary band-aid to get you out of trouble... sure, but doing this creates so many other problems with power/torque, exhaust emissions, cylinder/manifold wetting, misfires etc. The reason engineers designed sequential injection was to solve problems and improve design.

 

[Fu Manchu]

Well move on mate. Get over it because this is working for lots of people.

 

[Samoyed]

Well for about 4 weeks, the old vz started to idle rough. Got a scan done. Came up, 4 / 5 cylinder coil malfunction and 5 injector malfunction.
Replaced:

Coils.
Spark plugs.
Injectors.

Still no change.

Checked air flow sensor.
Checked throttle bottle etc.
Car doesn't over heat, also no blown head gasket. ECU?????

Car ran fine when hot.
So....
I checked ALL connections to coils, and the the injector connections.......and found number 5 injector wire (3v) had no current, so bridged that wire to number 4 cylinder, all works perfectly. Apart from the fault that still comes up, so my guess, with limited knowledge would be the ECU.

Thank you to those individuals who posted previously about this thread, although a quick fix, and by no means the correct one, it works, it does the job, until I get a few $$$, to possibly/ maybe get another ECU.
CHEERS

 

[Guardiana1]

G'day mate , New member here .
I worked for Holden for around 10 years total in parts and service , always owned Commodores , Dad 45 years for Holden as a mechanic and FJ's.

Just jumping on this thread as a first post as I just purchased a VZ last week with this exact issue ....shaking itself to pieces , engine powertrain light on, surging , trying to adjust itself to keep running at idle and outright terrible miss .

I was honestly looking to do this injector splice as a temporary fix as I thought "here we go" , plugs, coils, injectors , ecu etc etc was going to be the running $$ order for the next month .

Used a scan tool on her and found injector circuit /open cylinder 6.
After clearing all codes , had cylinder 5 injector circuit low pop up as well as the above cylinder 6 injector circuit .

HOWEVER
Popped the bonnet , took covers off and had my suspicions.
Checked all coils , no change .
It was then I noticed the tiniest white wire wrapped up hidden behind black electrical tape .

Someone had already done this injector bypass from 6 to 5 injector and wrapped her up and tried pushing the convolute back over . I'll give em that , was well hidden/done.

Long story .....
But I pulled the spliced wire free that had been soldered in to splice the 2 injectors and cut it in half .
PROBLEM SOLVED .
Car runs perfectly, codes cleared permanently, no return issue as yet .

So there is truth in the earlier comment on this thread by "mechanic" about it not necessarily being a good thing .
But also truth that it does work if it's really needed to get things running , by others posted here .

I just came by as a reader for years and thought it's worth signing up & mentioning my recent experience with this drama .

So it can most definitely work in reverse too..

Hope this helps anyone that just bought a 3.6l VZ , check for that injector bypass wire first as it too may have already been done & causing the issue as it was mine .

Cheers guys & good luck !!

 

[Fu Manchu]

So since it was done, someone actually fixed the original problem and the patch up caused the problems to continue.

Love the feedback. Great knowledge to share with others

 

[Guardiana1]

So since it was done, someone actually fixed the original problem and the patch up caused the problems to continue.

Love the feedback. Great knowledge to share with others

Cheers Fu Manchu, appreciate it mate .
This forum is an excellent source and the Go To for Commodore info . An honour to be able to give a bit back on this one and hopefully it might help someone out.

Spot on ! That's exactly what I think has happened brother .

I'd say by looking at it and the fact that I found two replaced coils (one hiding in the map pocket/ one in the cargo tool bay lol)
the patch has probably been done two owners ago or so maybe .

Previous two likely haven't been able to fix it and tried replacing no 6 coil twice over .
All other coils are original .
( Didn't want to take the manifold off maybe?)

I thought I was going to be in for a beauty , but turned out the OG patch as you said that originally had worked , was now the culprit.
Happy days . Cheers mate.

On a side note , this was one of those "always regularly serviced ", "runs great" sellers .
Oil classification : Got any blacker ?
(Likely 80k old)