Intermittent problem for the clever people

[hz2vl]

Alright here is one for the clever people.

My 86 VL has an intermittent problem that doesn't show up in the diagnostic codes.

Car starts normally, and drives fine for the 1st 3 minutes or so.
The lights in the ECU flash normaly to indicate closed loop tuning.

As the engine temp gauge starts to heat up, there is a period where the leds don't come on anymore.
If I try to accelerate during this period, the engine faulters and stall completely. I have learnt now to just sit by the side of the road for about 3 or 4 minutes, before the engine will start again.

When it starts, it runs rough for a couple of seconds, then comes good.

After this I can drive as far as I like without problems. But there is no indication of it entering the closed loop tuning mode.

Things I have checked: :b:
The Temp sensor has been checked and the plug replaced.
Checked all other plugs for corrosion or faulty connections.
Fitted fuel pressure gauge, checked pumps and replaced fuel filter.
Swapped ECU (exact same behavior).
Checked and rechecked diagnostic codes (nearly know them off by heart).

I have purchased a cathode ray oscilliscope to use to check Air Flow Meter, and Injector pulse signals. Just haven't had time yet.

Iwould really like to have my notebook computer discuss things with the ECU, to find out what is going on, but cannot find the necessary data on the communication protocols or data format. (I have got the plug to connect to the diagnostic plug).

Has anyone had a similar problem?
Does anyone have any other ideas?
Does anyone have any info on the data through the diagnostic plug on the firewall?

Any help would be greatly appreciated

 

[Doctor Bob]

try another o2 sensor?
this seems the next logical step as the system isnt going into closed loop
also i am pretty sure there is no data available from the ecu in these.
Rob

 

[Tasmaniak]

I know everyone screams the same thing, but could it be an earth problem on the ECU? If it happens intermittenly it can often be put down to a faulty wire somewhere...going high resistance. Not to sure when it comes to ECU's though.

 

[smada_85]

It might be your Crank angle sensor in the distributor. I had trouble with my vl it did 3 in 4 months but i got one with a 2 year warrenty from the auto elecs and its lasted a year so far. usualy you have the problem you are describing but after it is at oporating temp and worse above 2000rpm before it stalls. When mine died it didnt show up in the sefl diagnosis so it could be that. Its worth $160 for it though. Where is the plug for the ecu you were talking about? I didnt think that vl's had one.

 

[madsav]

have a look over on your starter motor, there is a creamy coloured wire there, if it comes off the car will run like a hairy goat.i know it took me 2 weeks none stop looking. i think the cream wire goes to the solonied or sumthing

 

[GMH-JC]

Try The O2 Sensor

 

[michaelw]

Check the wiring and the conectors. You have a 18+ year old car, think of all the stress the wires have had. With the engine running "wobble" each conector to see if it corosponds to any fault. Also the contacts might be dirty, buy a can of "co contact cleaner" we call it "electrical make work now".

Mike

 

[seventh path]

there's no data plug to check codes....they came later, you have to rely on the led's.......i had a similar problem a few years back and it was the plug on the crank angle.........it would run rough, stop and then wait and it would start again........but the times i had to wait varied and the last time i had to wobble all the plugs to make it start....

 

[hz2vl]

Thanks (So Far)

Thanks for the good suggestions, ideas.
I will be getting to it again this weekend.

About the diagnostic plug/s.
There is one on a manual,, and two on an automatic.

The engine one is a four pin socket under the bonnet, against the firewall on the passenger side.
So far I have found out that there is an earth, and a 12V power wire.
I have only guessed that the other 2 are data in and data out, as they go directly to the ECU, but I hope to investigate further this weekend, if I don't do too much :drink: .

The gearbox one is a six pin socket under the bonnet, against the firewall on the drivers side. Manual cars don't have this.
Three of these pins share the connection to the three gearbox solenoids, so they have power on them when the gearbox ECU operates the solenoids. I haven't investigated this any further yet.
I am thinking about putting a couple of LEDS on these so I can see if the gearbox is responding when its brain tells it to.

I will keep you informed as more details are collected.

 

[hz2vl]

A Win

Good People
I found a fault, and I can't believe that I cannot find any mention of it in any forums.

In an effort to protect VLs from people that do stuff wrong, holden saw fit to include a 'Reverse Polarity Relay'.

The idea is if someone puts the battery in the wrong way round, and puts the big red clamp on the blue/black terminal, and the black clamp on the red terminal, then this relay operates and open circuits the injectors and one power feed to the ECU.

In the life of the car this relay should never operate.

What it meeans though is that all power to the injectors is via this relay.

It is mounted behind the battery in a good spot to get splashed with acid when the battery gets washed.

Mine was lying loose when I bought the car, and I did the right thing and screwed it back against the mudguard. (Didn't know what it was at that stage).

I was checking stuff, and going over the circuits, as was suggested in this forum, and found mine had a problem. (See attached photos).

It has now been replaced with a piece of 2.5mm wire with two spade terminals as a temporary measure.

This morning it ran the best it ever has :yeah:

I think this check/test should be included for all to read, but I don't know where it should go in the forums.

I have also fitted a single LED, O2 operation detector, that can be made using less than $10 worth of new bits (cheaper if you have some electronic experience/bits). It is ON when the injectors are in 'shutdown' (coasting above a certain number of revs), OFF when in OPEN LOOP (Flooring it), and FLASHING when in CLOSED LOOP (when the ECU is tuning for economy). This is indicating that my O2 sensor is working fine until it has heated right up. I will investigate this further, but I think I will need a new O2 sensor.

I now feel I can get onto some other niggly problems that are annoying me.

Does anyone know anything about the heater hoses?