Discussion
Give up with the digital test meters- if you are measuring across the injectors you have 12v on one side, and a 12 v signal on the other that drops to 0 for the duration of the injectors being open. A DVM rapidly scans the voltage and tries to average it out for the display- so how will this work if one millisecond its at 12v, the suddenly at 0 next scan? It will be coincidental if its 12v or 0 v when the DVM scans so no reading will be accurate or reliable, you really are making life hard for yourself . If carting a laptop about is a pain, get a cheap windows 10 tablet and usb adaptor and leave RG connected and running. Any screen shots of long / short term fuel trim need to be done on a warm engine. Your screen shots look like everything is stone cold, and the lamdas need heat to give a readings and start working. You can turn on all the sensors if you are just watching what goes on, but for logging, Id limit them to the ones i suggested or the total data from the sensors makes setting up spread sheet to read them gets difficult..
In terms of what affects the injector timing- both banks start with the same pulse width, but its then tweeked depending of what the lambda feedback is doing. This instantaneous tweak is the short term trim, so it should constantly cycle around a mid point add / remove fuel if things are well. If its constantly adding or removing fuel, then something is out of spec'. The long term trim is only active at idle to set the basic fuelling up if the short term trim is cycling too far one way, and takes at least 2.5 mins to stabilise on a hot engine, If the engine is below about 90'c it wont alter The long term trim becomes locked once you use the throttle and increase the revs and will only move again next time (if needed) the engine idles
Mind you, before you get too bogged down, do the basics- take out all 8 spark plugs and compare the colours. If one bank is fuelling incorrectly the plugs will all be a different colour, and also don't forget RoverGauge is a fuelling / ECU tool and wont pick up ignition faults easily. It also only logs fuelling faults after some minutes of poor running if the lambda outputs stop cycling completely. If they keep switching, even badly, then no fault code is logged. If you want to use 2 DVMs, then put wires on the lamda outputs black and white wires, (both sides) and run the cable back into the cabin to the DVM. On a warm engine they should cycle between 0 and 1.2 to 1.4 v, a DVM can read this slow signal. The switching at idle is very slow- it can be seconds, but should increase to about 1/2 a second as the RPM rises. If the output voltage sicks at 0 when the fault occurs, you have too little fuel, or if it sticks over 1.2 its too much.
Here is a set up with an analogue gauge that works a treat I built before RoverGauge to read the voltages:
In terms of what affects the injector timing- both banks start with the same pulse width, but its then tweeked depending of what the lambda feedback is doing. This instantaneous tweak is the short term trim, so it should constantly cycle around a mid point add / remove fuel if things are well. If its constantly adding or removing fuel, then something is out of spec'. The long term trim is only active at idle to set the basic fuelling up if the short term trim is cycling too far one way, and takes at least 2.5 mins to stabilise on a hot engine, If the engine is below about 90'c it wont alter The long term trim becomes locked once you use the throttle and increase the revs and will only move again next time (if needed) the engine idles
Mind you, before you get too bogged down, do the basics- take out all 8 spark plugs and compare the colours. If one bank is fuelling incorrectly the plugs will all be a different colour, and also don't forget RoverGauge is a fuelling / ECU tool and wont pick up ignition faults easily. It also only logs fuelling faults after some minutes of poor running if the lambda outputs stop cycling completely. If they keep switching, even badly, then no fault code is logged. If you want to use 2 DVMs, then put wires on the lamda outputs black and white wires, (both sides) and run the cable back into the cabin to the DVM. On a warm engine they should cycle between 0 and 1.2 to 1.4 v, a DVM can read this slow signal. The switching at idle is very slow- it can be seconds, but should increase to about 1/2 a second as the RPM rises. If the output voltage sicks at 0 when the fault occurs, you have too little fuel, or if it sticks over 1.2 its too much.
Here is a set up with an analogue gauge that works a treat I built before RoverGauge to read the voltages:
Hi Blitzracing, thanks for the thoughts, can I just confirm that the cheap tablet needs to be windows 10?, they obviously get cheaper still at windows 8 and I have no other use for it as I have an Android already.
I fully agree with your thoughts about measuring a PWM signal on a multimeter and obviously it cannot read an absolute figure, but I must say that from trying it does display a very stable signal that rises and falls smoothly with the revs so it looks like it at least has relative value, but I have seen enough from that anyway now, looking on the web DVM/ scopes can be had quite cheaply with at least the ability to save screenshots.
While poking around looking at the lambda cable I saw that there is another identical connector under the plenum, is this normal??.
You mentioned the long term maybe taking 2.5 mins to fully reset itself, that seems very close to how long my issue occurs ?
So what would happen if I lost my lambda signal for a short time?, how long before the ecu gave me a load of fuel to compensate??
Penelope, I see you frequently have alternative views so feel to express those
Time is running short now for this year so not sure how many more chances I will get for testing as I intend to tidy up the engine Bay Area over the winter period
I fully agree with your thoughts about measuring a PWM signal on a multimeter and obviously it cannot read an absolute figure, but I must say that from trying it does display a very stable signal that rises and falls smoothly with the revs so it looks like it at least has relative value, but I have seen enough from that anyway now, looking on the web DVM/ scopes can be had quite cheaply with at least the ability to save screenshots.
While poking around looking at the lambda cable I saw that there is another identical connector under the plenum, is this normal??.
You mentioned the long term maybe taking 2.5 mins to fully reset itself, that seems very close to how long my issue occurs ?
So what would happen if I lost my lambda signal for a short time?, how long before the ecu gave me a load of fuel to compensate??
Penelope, I see you frequently have alternative views so feel to express those
Time is running short now for this year so not sure how many more chances I will get for testing as I intend to tidy up the engine Bay Area over the winter period
Windows 8 should be OK, but its not called Windows Hate for no reason. Never got my head around it personally. You can get RoverGauge on android to run on your phone, but it takes a bit more setting up, you basically need to decide what readings you want to make up a display.
https://www.pistonheads.com/gassing/topic.asp?h=0&...
As for the cable- its extended by TVR so quite normal- you can tap wires from either connectors by pushing nails in down beside the internal connectors. The problem you have at the moment is if you think the injector timing is changing and causing the fault, the ECU must be making that change for a reason. Getting voltages direct from the lamdas is a really quick way of looking at the fuelling without getting to bogged down in RoverGauge, but your fault wont be anything to do with the long term trim. It could for example be a misfire- the Lambda probes see unburnt mixture as a lean mixture as they both have lots of oxygen in the exhaust, so the ECU pops in lots more fuel, that wont fix anything as its not being burnt. The ECU is supposed to be able to pick up misfires in the left or right bank, but its really not that smart to pick out a single cylinder. It really only flags errors when the fuelling is so bad the lambda probes stop switching, typically over a couple of minutes.
https://www.pistonheads.com/gassing/topic.asp?h=0&...
As for the cable- its extended by TVR so quite normal- you can tap wires from either connectors by pushing nails in down beside the internal connectors. The problem you have at the moment is if you think the injector timing is changing and causing the fault, the ECU must be making that change for a reason. Getting voltages direct from the lamdas is a really quick way of looking at the fuelling without getting to bogged down in RoverGauge, but your fault wont be anything to do with the long term trim. It could for example be a misfire- the Lambda probes see unburnt mixture as a lean mixture as they both have lots of oxygen in the exhaust, so the ECU pops in lots more fuel, that wont fix anything as its not being burnt. The ECU is supposed to be able to pick up misfires in the left or right bank, but its really not that smart to pick out a single cylinder. It really only flags errors when the fuelling is so bad the lambda probes stop switching, typically over a couple of minutes.
Edited by blitzracing on Monday 23 September 18:08
Thanks for the link, I will give Android a go and see if I can ask it to read as you recommended previously
I hadn’t figured on a misfire or such being able to signal more fuel, how would the ecu get out of what sounds like an ever worsening loop ?, if that was the case though would the lambda stopping cycling give me an alarm code?
If only one cylinder was misfiring would I easily notice that?, I’m sure I have read about people running on seven and not being aware of it, or have I just dreamt that up?., but on that note I was just thinking that I have never noticed a misfire beforehand but it’s possible that it always comes after lifting off the throttle and then noticing the big loss of oomph when re applying, but I’m not 100% certain on that one.
So the lambda sensor signal needs to change for a couple of minutes to change the output, to see that I really need to record it or have a small display on the steering column or dash top due to the very intermittent nature
I hadn’t figured on a misfire or such being able to signal more fuel, how would the ecu get out of what sounds like an ever worsening loop ?, if that was the case though would the lambda stopping cycling give me an alarm code?
If only one cylinder was misfiring would I easily notice that?, I’m sure I have read about people running on seven and not being aware of it, or have I just dreamt that up?., but on that note I was just thinking that I have never noticed a misfire beforehand but it’s possible that it always comes after lifting off the throttle and then noticing the big loss of oomph when re applying, but I’m not 100% certain on that one.
So the lambda sensor signal needs to change for a couple of minutes to change the output, to see that I really need to record it or have a small display on the steering column or dash top due to the very intermittent nature
Paulprior said:
Penelope, I see you frequently have alternative views so feel to express those
Nothing to do with my viewsThere are correct and incorrect methods of testing and the methods that you are using are incorrect
Connecting volt meters to injector signal cables is not the correct method
blitzracing has above explained why in detail
Circuit voltages need to be checked directly at the components that could be causing the problem before delving deeper
Paulprior said:
As I have already said, I completely agree with what Blitzracing has to say and why, unfortunately I do not agree with your last paragraph, measuring at source or destination shows different things sometimes, rather than right or wrong.
This is all very basic to me and I fully understand how it may not be for theeDue to the fault being Intermittent
If the Inputs (Positives and Negatives) at the components (Lambda Sensors) haven't been proven good, it is a total waste of time checking the outputs
If the Inputs (Positives) at the components (Fuel Injectors) haven't been proven good, it is a total waste of time checking the Lambda Sensor outputs
If the cables from ECU to Injectors (Negative Switching) haven't been proven good, it is a total waste of time checking the Lambda Sensor outputs
I hope for your benefit that it isn't unfortunate for you to disagree with my methods of testing
Paulprior said:
Thanks for the link, I will give Android a go and see if I can ask it to read as you recommended previously
I hadn’t figured on a misfire or such being able to signal more fuel, how would the ecu get out of what sounds like an ever worsening loop ?, if that was the case though would the lambda stopping cycling give me an alarm code?
If only one cylinder was misfiring would I easily notice that?, I’m sure I have read about people running on seven and not being aware of it, or have I just dreamt that up?., but on that note I was just thinking that I have never noticed a misfire beforehand but it’s possible that it always comes after lifting off the throttle and then noticing the big loss of oomph when re applying, but I’m not 100% certain on that one.
So the lambda sensor signal needs to change for a couple of minutes to change the output, to see that I really need to record it or have a small display on the steering column or dash top due to the very intermittent nature
The lambda switching is pretty crude at best, not helped by TVR putting them downwind of the precats. The ECU will simply crank up the fuel with a misfire to try and get the lambdas to cycle evenly, but of course it wont ever if its not being burnt. The ECU has I believe about 20% ability to change the mixture, so the idea would be it runs out of its 20% and then flags an error. The truth is its simply not that sensitive- as the firing cylinders will now be low in oxygen as the mixture is far too rich, but mixed with unburnt mixture with excess oxygen it may look just fine to the ECU, so no fault codes. The later GEMS ECU can pick it up accurately as it counts pulses off the starter ring, and when a cylinder misfires the pulse rate drops for just that 90' of Crank cycle. If you want a simple display for the Lambda voltages you can use a LED VU meter, but set to read up to 1.5 volts. The easiest option however is an cheap analogue mutimeter, as it physical movement can show you the cycle rate nicely, if you can get one with a full scale reading at 2.5 volts DC. I hadn’t figured on a misfire or such being able to signal more fuel, how would the ecu get out of what sounds like an ever worsening loop ?, if that was the case though would the lambda stopping cycling give me an alarm code?
If only one cylinder was misfiring would I easily notice that?, I’m sure I have read about people running on seven and not being aware of it, or have I just dreamt that up?., but on that note I was just thinking that I have never noticed a misfire beforehand but it’s possible that it always comes after lifting off the throttle and then noticing the big loss of oomph when re applying, but I’m not 100% certain on that one.
So the lambda sensor signal needs to change for a couple of minutes to change the output, to see that I really need to record it or have a small display on the steering column or dash top due to the very intermittent nature
https://www.ebay.co.uk/itm/YX-360TR-Es-Analogue-Me...
Edited by blitzracing on Wednesday 25th September 19:38
So I did as recommended and measured the pulses on the black and white cables on the left Lambda, the needle was quite slow to move and never reached more than 1V before dropping off again, frequently the pulse never reached more than about 0.2 to 0.3V, I also decided to see what would happen if I disconnected the lambda, absolutely nothing that I could notice, I guess that means that a bad sensor or cable cannot be causing my issue ?.
Just out of curiosity, what causes those pulses in terms of timing and output??
Time to try and get RG on Android I guess
Just out of curiosity, what causes those pulses in terms of timing and output??
Time to try and get RG on Android I guess
I have also been looking at scopes, there are quite a lot to choose from for very little money, many state that they have a recording function but no one yet has responded to being asked if the recording is a continuous time logged trace or just screenshots?
What is the reason for the occasional unusual waveform on that display ?, for info I have the precats removed and the main one still in
What is the reason for the occasional unusual waveform on that display ?, for info I have the precats removed and the main one still in
You could also get something very portable like this
https://www.ebay.co.uk/itm/Mini-DSO-Portable-DS211...
Or a scope / DMM
https://www.ebay.co.uk/itm/Upgraded-MUSTOOL-MT8206...
https://www.ebay.co.uk/itm/Mini-DSO-Portable-DS211...
Or a scope / DMM
https://www.ebay.co.uk/itm/Upgraded-MUSTOOL-MT8206...
Its one of these units built into a 14CUX case. This sits in parralell with the cars ECU so I can grab any sensor signal on the way in. The logger is not quite fast enough for ignition pulses though.
https://www.ebay.co.uk/p/Velleman-K8047-4-channel-...
[
I liked it as it grabs 4 channels at once easily and takes very little setting up, unlike my Pico scope.
This is left and right lambda AFM and TPS
https://www.ebay.co.uk/p/Velleman-K8047-4-channel-...
[I liked it as it grabs 4 channels at once easily and takes very little setting up, unlike my Pico scope.
This is left and right lambda AFM and TPS
Edited by blitzracing on Thursday 3rd October 17:11
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