Rough running

[Paulprior]

I have been running on the replacement LR ECU for a few weeks but only short journeys and all ok, however, yesterday i went out for a 100 mile run, it started ok for maybe 20 miles, then i had the normal rough running, followed by a few hiccups, followed by a complete cut out, i did the normal reset of the immobiliser and carried on, by the time i had reached 40 miles a more severe misfire occured to the extent that i could not carry on because of severe shunting, so i pulled over and refitted my original ECU and just laid it on the carpet, the other had been beside the battery, it took a little while to start, only fired after putting the accelerator to the floor, i continued my journey, stopped for lunch and then drove back in which time it ran perfectly.
So to me it still looks like a overheat problem, but i cant believe the second ECU has exactly the same issue, any ideas ?????

For Rover Gauge, can i hook it up and record, or do i need to take screenshots when running good and bad ??

Paul

[Paulprior]

So back on my original ECU, still thinking about heat so i fixed it with velcro to the battery box and didnt enclose it, took it for a 60 mile trip yesterday and by 40 miles it played up in various ways several times, pulled over and laid it on the floor, the rest of the journey and the same trip back and it ran perfectly.
took it for a little drive today to warm it up and started exploring the cables etc near the ecu, at one point the engine started running badly, play again with the cables but i cant stop it, opened the bonnet and measured on the outside of the precat area and measured 270 drivers side, 170 passengers side, after a few minutes it started working again as it always does, tried messing with the cables again but i could not repeat the fault.
So what can one cool manifold mean, no spark but as far as i know these are common apart from the HT leads to all cylinders.
Fuel pressure i believe is common to both sides.
Injectors are switched per side, so maybe not working or permanently open ??, i believe the 12V is common but obviously splits somewhere, so maybe a fault after the split, is there any reasonably easy way to run another cable and join somewhere?
the ground goes back through the ECU, i guess a break or a short here would cause the problem, again, is there an easy way to run another cable for testing?
Can RG show me something if i work out how to use it?, i do have the software and cable??
Any other thoughts??, my wife is suggesting i should consider buying a more reliable vehicle, obviously i said no to this, its very frustrating because i know its going to be a stupid little thing when i eventually find it

[Paulprior]

I found the loom with injector wiring, but not exactly easy access as it’s below the plenum, so I gained access to the wiring in the tunnel as far as possible and everything looks very good, started the engine and pushed, pulled, twisted and swung around as much as possible but to no effect, now confused, I was certain it had to be the ecu or cabling close to it, only thing I can think of now is to make a breakout lead into the injector connector to confirm that they are on continuous or off when I get the misfire

[Paulprior]

Some very interesting comments

To Steve I would be very grateful if you would update me as you hopefully progress, I will certainly try that as soon as I get home, it will be a good excuse for a drive

As for Loubaruch interference possibility I will check the case earthing, and should I admit to still having the original metal plug extenders??, I will fire her up at night and look for any sparks, but an interesting theory

Finally thanks to Dr Mike Oxgreen for a new word to explain a very unusual plug numbering system that I have never seen before, just not sure when I will ever use this new knowledge, but we will see

Thanks guys for some directions that I had not considered

[Paulprior]

Hi FoxTVR430
Thanks for the thought, but yes tried that one and all ok

[Paulprior]

I have tried out the previous suggestions, checked that the ecu is earthed, the internals are ok, removed the plug cover and seal, but still no change, so In the absence of a scope I connected up some multimeters to measure the voltage to the injectors, measured st the supply from the main relay as well as the ecu ground switching on pins 11 and 13, when driving normally this results in a supply voltage of high 13s and the switching being low 13v at Rickover and dropping as the revs rise, circa 10v at 3000rpm, yesterday while ticking over it started to run rough while in the garage, as soon as it started I get the below
The left meter is the left bank of injectors, central is the right bank, right is supply voltage
After maybe 1 or 2 minutes I get the below signals

Then onto this

At this stage it coughing and spluttering as if it’s nearly working, then finally this when it’s running smoothly again

So it looks like the left bank is firing for too long and flooding, then after a few minutes it gradually resets back to normal, this is the way it always happens and looks to be controlled in doing so, does anyone have any idea why the left bank decides it suddenly needs a lot more fuel than it should ??

[Paulprior]

Thanks Blitzracing, I will try and do that, for my understanding, what are “short and long term trim “
The difficulty is going to be catching it with the laptop connected, I guess I will need to connect every time and run and maybe only start logging when the problem happens and stop it when it clears, is there a time stamp with the log so we can compare against the time when the problem starts and stops ??
I seem to recall discussions about running RG on a tablet, is that a possibility ??

[Paulprior]

Thanks for that Steve, I will connect RG and hope to record on its next rough running although due to the intermittent nature it could be some time before I respond again, but one question, the Lambdas are individual per bank, is it possible that s dodgy signal from one of these could cause such a big fuelling error ??

[Paulprior]

So I have RG hooked up, I’m not reading anything for engine temp or fuel temp, is that normal??, on the dash I have 80 deg
Is the page setup correctly for what I need to be displaying, long term or short term ??

[Paulprior]

Thinking about it, it could be that as i was going to make a log file while driving i switched off most parameters as recomended by Blitzracing, i assumed that this would only affect the log, but i guess its the display as well, i will try again tomorrow

[Paulprior]

Following the comments above i have swapped over the Lambda sensors and been driving around with just 2 multimeters connected to measure the injector signal as best as possible, an indication at least, as well as having RG hooked up most of the time, i have covered around 500 miles without any fault at all until yesterday, about a mile from home after a great days driving, Lake Bala, the Evo triangle, Horseshoe pass and the Ponderosa.
Un fortunately i didnt have RG connected up yesterday, the missus is getting a bit fed up with laptops and multimeters, and when the fault happened the meters were on the floor and she had somehow pulled the leads out, so i stopped quickly, connected the leads, left bank has a lower voltage, left hand manifold colder
Rg shows no alarm of any sort, from that can i conclude that they are good, especially after swapping them around, what would the RG or the ECU need to see to set an alarm?.
So Hypothetically what could be my possibilities if i assume that i am overfuelling on the left bank and the time taken running rough is the time the ECU takes to reset its long term trim to be in the right area?, if that is a possibility what could cause the issue to start with, a dodgy sensor cable from Lambda to ECU ???, if so how long does that signal need to be low, just a few seconds or less for a bad connection???
Any thoughts welcome as always

[Paulprior]

Measured at battery earth on all, main voltage measured at the main relay, injectors at the ECU, pins 11 and 13 I think

[Paulprior]

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

[Paulprior]

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

[Paulprior]

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.

[Paulprior]

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

[Paulprior]

Yes the earth is good at back of the block, I have even run an earth strap from there direct to the battery negative

[Paulprior]

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

[Paulprior]

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...

[Paulprior]

That looks a very useful tool, just unfortunate its not quite fast enough for the injector signals which i really need to clarify, this looks like it should do the job at a decent price, what do you think?