Monday, August 02, 2010 - 03:34 pm, by: Graham Pearce(Grasoar)
Hi Everyone, My V8 appears to be running rich, with lumpy idle, black exhaust smoke and a pronounced intermittent miss when cruising.
Plugs and leads have been replaced, but the inner 2 cylinders on each bank (ie 3,4,5 & 6) keep sooting up while the other 4 are fine.
A mechanic who checked the car said the inner injectors are delivering fuel at 50 times the rate of the outer ones, but he had no idea what was causing it. He felt that it might be the ECU but not a sensor as that would affect all cylinders.
I have tried running diagnostics as outlined on this site, but can't get them to work. An "engine electrical system" error message appears each time the motor is started.
Monday, August 02, 2010 - 03:55 pm, by: Daniel Arndt(Darndt)
First and cheapest option would be to borrow an known working ECU and see if that fixes it. If it is ECU maybe just needs the caps replaced. But check it first with a working one before you do.
Monday, August 02, 2010 - 07:29 pm, by: Nathan Richardson(Richtheblack)
I agree with Nik and Tom, that would be the first place I'd look.
Try disconnecting one coil whilst idling, if no change, that might be the problem. Disconnect the other, if the engine stalls or gets worse, that one is probably good.
How did your mechanic check the injectors? Did he test their duty cycle or pulse rate or just speculate?
Tuesday, August 03, 2010 - 06:51 am, by: Daniel Arndt(Darndt)
Ah yes, coil and ignitor. For some reason I had the idea that each coil served one bank. but then why would there be high tension leads crossing over each bank. So one coil would then serve 2 cylinders on each bank? I think Tom and Nick are on the right track.
Tuesday, August 03, 2010 - 03:10 pm, by: Graham Pearce(Grasoar)
Thanks for the suggestions, guys. I just checked the coil and resistance readings are ok.
Nathan, the mechanic had the car in his workshop for a few days and he said the inner injectors were running at 50 times the frequency of the others, so I presume he was talking pulse rate. He also admitted he was stumped as to what would affect just the inner cylinders.
Tuesday, August 03, 2010 - 05:54 pm, by: Tom Richards(Tomr)
graham, there are 2 coils , did you check both? also check the HT lead from the coil to the disti. It is short so should only read a couple of K ohms. I have seen one that had burnt away at the coil end so have a good visual as well as measuring them
Peter Nitschke Junk Filterer South Australia UZZ30 UZZ31
Tuesday, August 03, 2010 - 10:33 pm, by: Peter Nitschke(Pen)
ECU for sure, an injector pair is virtually on all the time. Swap it with a known good to prove it. Apparently there is also a driver chip that can go faulty and turn injectors on - in pairs, but in my case replacing the caps fixed it.
Monday, September 13, 2010 - 07:11 am, by: Daniel Arndt(Darndt)
Graham, that's great to see your problem resolved. What do you mean by overhauled? I'm about to replace all the Caps in mine. Is that all you have done? There is nothing wrong with mine currently, but for the cost and time I believe its good preventative maintenance. I found this diagram, could anyone advise if is correct for the uzz31?
Thursday, September 16, 2010 - 10:36 am, by: Graham Pearce(Grasoar)
Daniel, the overhaul would normally involve replacing the caps as well as any other faulty/ suspect components but I had already replaced them. Apparently there was some other fault in my case.
I agree that replacing the caps is good preventative maintenance especially if you clean the board thoroughly while you're at it.
From memory, your layout picture is the same as mine, though I have been told that ECUs varied over the years. (Mine is a 91.)
Thursday, October 28, 2010 - 10:32 am, by: Graham Pearce(Grasoar)
Ian, sorry about this belated reply, but I haven't had a chance to get online for the past few weeks.
Injectronics http://injectronics.com.au did the work. Apparently they will only deal with you via their agents. Here in Coffs Harbour I used Bursons, but I believe Repco also has an agency.
It cost me $670, but this could vary depending on what work is required and how much commission the agent decides to add on top.
Thursday, October 28, 2010 - 10:50 am, by: Daniel Arndt(Darndt)
OUCH. $670 for a rebuild of the ECU. I'm in the wrong business. Graham you should have just looked for a second hand ECU. I'm about to replace the caps in mine over the Christmas break. Just preventative maintenance though.
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