Voltage Drop via ECU

[WIL35]

Have linked up to a laptop to try and find out why my 4.2 keeps backfirng and popping when it is idling.

The Voltage level via the ECU is only about 9-10V, I've checked the battery and both sides of the big fuse with a voltmeter and they are all showing 12.22V!

What would cause this difference?

[marcus1970]

WIL35 said:

Have linked up to a laptop to try and find out why my 4.2 keeps backfirng and popping when it is idling.

The Voltage level via the ECU is only about 9-10V, I've checked the battery and both sides of the big fuse with a voltmeter and they are all showing 12.22V!

What would cause this difference?

Don't know.

However, my guess on the popping/backfiring is that you may need to reset your throttle pots. At an even bigger guess, are your adaptives well down into the minuses?

MB

[WIL35]

One of the adaptives is negative the other is positive. When the engine isn't running TP is set at 18 on the bank with the negative adaptive and the TP on the bank with the positive adaptive flickered between 17.8 and 18.4.

[marcus1970]

WIL35 said:

One of the adaptives is negative the other is positive. When the engine isn't running TP is set at 18 on the bank with the negative adaptive and the TP on the bank with the positive adaptive flickered between 17.8 and 18.4.

You'll probably find that the negative side is the one that pops and bangs the most on idle. It's quite common for it to be one side more than the other. How negative is it?

Mine was popping like a goodun on the even bank on warm idle, with the adaptives showing around -30 to -37.5 (very negative).

I moved the throttle pot down a notch or two on that bank and the adaptives went down considerably. I now have a warm idle of around 1000rpm and no pops and bangs unless the engine is on uverrun.

It's not perfect, but it's much better and I'll give it a tweak when time permits.

MB

[ridds]

I'd check and clean your earths.

[WIL35]

marcus1970 said:

WIL35 said:

One of the adaptives is negative the other is positive. When the engine isn't running TP is set at 18 on the bank with the negative adaptive and the TP on the bank with the positive adaptive flickered between 17.8 and 18.4.

You'll probably find that the negative side is the one that pops and bangs the most on idle. It's quite common for it to be one side more than the other. How negative is it?

Mine was popping like a goodun on the even bank on warm idle, with the adaptives showing around -30 to -37.5 (very negative).

I moved the throttle pot down a notch or two on that bank and the adaptives went down considerably. I now have a warm idle of around 1000rpm and no pops and bangs unless the engine is on uverrun.

It's not perfect, but it's much better and I'll give it a tweak when time permits.

MB

Yes it is the offside bank that is popping, with a negative adaptive of about -13. It is also spitting out black stuff from that exhaust pipe.

I've cleaned the earths that go to the chassis behind the nearside front wheel.

Marcus, when you said you put the TPs down, how much was it? Was it down to 15?

[Tokyokev]

Sorry to jack this thread, but I also have two black streaks on my rear - seems to be tiny black spots spitting out....not oil, more like dryish soot.

Running too rich?

K


Sorry forgot to add that I just cleaned the air filter as it was gunked up, and now the black spotting has reduced significantly.

Edited by Tokyokev on Friday 22 June 06:24

[marcus1970]

WIL35 said:

marcus1970 said:

WIL35 said:

One of the adaptives is negative the other is positive. When the engine isn't running TP is set at 18 on the bank with the negative adaptive and the TP on the bank with the positive adaptive flickered between 17.8 and 18.4.

You'll probably find that the negative side is the one that pops and bangs the most on idle. It's quite common for it to be one side more than the other. How negative is it?

Mine was popping like a goodun on the even bank on warm idle, with the adaptives showing around -30 to -37.5 (very negative).

I moved the throttle pot down a notch or two on that bank and the adaptives went down considerably. I now have a warm idle of around 1000rpm and no pops and bangs unless the engine is on uverrun.

It's not perfect, but it's much better and I'll give it a tweak when time permits.

MB

Yes it is the offside bank that is popping, with a negative adaptive of about -13. It is also spitting out black stuff from that exhaust pipe.

I've cleaned the earths that go to the chassis behind the nearside front wheel.

Marcus, when you said you put the TPs down, how much was it? Was it down to 15?

Don't forget yours is a 4.2 so they will be a tad higher than mine. Don't get caught up on the text book figures - they are a good starting point, but as each engine wears etc things change. Personally, from what you say, I'd probably only move it so it drops to around 17.5'ish and see what you get. -13 doesn't sound too bad. What are your lambdas telling you? Nearer 1.5 or 0.3/5?

MB

[marcus1970]

Tokyokev said:

Sorry to jack this thread, but I also have two black streaks on my rear - seems to be tiny black spots spitting out....not oil, more like dryish soot.

Running too rich?

K


Sorry forgot to add that I just cleaned the air filter as it was gunked up, and now the black spotting has reduced significantly.

Edited by Tokyokev on Friday 22 June 06:24

Mine was chucking out black bits as it was running too rich. Cleaning out the air filter etc will help as it means more air to mix with your fuel.

MB

[Tokyokev]

marcus1970 said:

Tokyokev said:

Sorry to jack this thread, but I also have two black streaks on my rear - seems to be tiny black spots spitting out....not oil, more like dryish soot.

Running too rich?

K


Sorry forgot to add that I just cleaned the air filter as it was gunked up, and now the black spotting has reduced significantly.

Edited by Tokyokev on Friday 22 June 06:24

Mine was chucking out black bits as it was running too rich. Cleaning out the air filter etc will help as it means more air to mix with your fuel.

MB

thanks marcus...I think the throttle pots need a fiddle and maybe Lambda sensors...am gonna put it into the garage in a couple of weeks.

K

[Peppe]

WIL35 said:

Have linked up to a laptop to try and find out why my 4.2 keeps backfirng and popping when it is idling.

The Voltage level via the ECU is only about 9-10V, I've checked the battery and both sides of the big fuse with a voltmeter and they are all showing 12.22V!

What would cause this difference?

Hi !

If you look at the wiring diagrams you will see that the 12V supply for the ECU goes from the battery to the rear of the car and then back too the ECU in the passenger footwell. On its way it passes the 100A fuse under the dashboard, about 5 connectors, ignition control module, fusebox and imobiliser, im not sure about the imobiliser.
I had a very noisy 12V going to my ECU and a voltage drop of about 1-2V. After that i had been trying to clean all connectors and so on, i cured the problem by putting an extra relay in for the ECU 12V (Found that solution here on PH). The car runs smother and better after that i made this change.

// Peppe

[SimonSparrow]

Peppe said:

WIL35 said:

Have linked up to a laptop to try and find out why my 4.2 keeps backfirng and popping when it is idling.

The Voltage level via the ECU is only about 9-10V, I've checked the battery and both sides of the big fuse with a voltmeter and they are all showing 12.22V!

What would cause this difference?

Hi !

If you look at the wiring diagrams you will see that the 12V supply for the ECU goes from the battery to the rear of the car and then back too the ECU in the passenger footwell. On its way it passes the 100A fuse under the dashboard, about 5 connectors, ignition control module, fusebox and imobiliser, im not sure about the imobiliser.
I had a very noisy 12V going to my ECU and a voltage drop of about 1-2V. After that i had been trying to clean all connectors and so on, i cured the problem by putting an extra relay in for the ECU 12V (Found that solution here on PH). The car runs smother and better after that i made this change.

// Peppe

Sounds good, did you just run 12v from the battery to the ECU (switched by the original 12v feed to the ECU)?

[Peppe]

SimonSparrow said:

Peppe said:

WIL35 said:

Have linked up to a laptop to try and find out why my 4.2 keeps backfirng and popping when it is idling.

The Voltage level via the ECU is only about 9-10V, I've checked the battery and both sides of the big fuse with a voltmeter and they are all showing 12.22V!

What would cause this difference?

Hi !

If you look at the wiring diagrams you will see that the 12V supply for the ECU goes from the battery to the rear of the car and then back too the ECU in the passenger footwell. On its way it passes the 100A fuse under the dashboard, about 5 connectors, ignition control module, fusebox and imobiliser, im not sure about the imobiliser.
I had a very noisy 12V going to my ECU and a voltage drop of about 1-2V. After that i had been trying to clean all connectors and so on, i cured the problem by putting an extra relay in for the ECU 12V (Found that solution here on PH). The car runs smother and better after that i made this change.

// Peppe

Sounds good, did you just run 12v from the battery to the ECU (switched by the original 12v feed to the ECU)?

Yes thats how i did it. Just remember to put a fuse in between, i do not remember what amp i used on the fuse but it was the same as the one that is for the ECU in the fusebox.

Peppe

[SimonSparrow]

I'm thinking about doing this over the next couple of weeks when I get some time, exactly how have you guys done it? I've found out that pin 6 on the ECU connector is power, but have you fed 12v straight into the ECU connector, or further 'upstream' in the wiring harness?

I'm also thinking or running a dedicated earth wire to the ECU/battery - has anyone done this?