Poor idle and stalls + onboard computer fuel use

[pcspinheiro]

Thank you for that info! Then that is the only sensor (and the one I unplugged) which makes it weird that the coolant temp was showing so low when looking at the live sensor data if the dash shows correctly... And then again the ECU should be revving the engine up if it thought it was cold... Hum... I think what I will try next is to clear all fault codes (they cannot be cleared with the engine running for some reason) then monitor simultaneously, at idle, the RPM and relevant sensor data like idle valve, throttle position, inlet pressure, etc, to see if one of those has changes that match the brief surges in RPM. Then test again while driving and see which ones follow the sinking of the RPM when shifting. Unless the new ECU was programmed wrong when the previous owner had to change it there must be something there!

By the way, do you get those diagrams from the Citroen service box DVDs or from logging in to their website? I found them for download "elsewhere", is this free information or an illegal download?

Best wishes,

Paulo.

[Mandrake]

I honestly don't remember by heart how I got to graphing the data but it was when you go to live sensor data then there is a bouton that looks like a graph with a sine wave, if you click that you can choose up to 6 parameters to record. Press record or start, don't remember, then stop and it will display. Don't try to use the save to disk button, I did and it just made lexia crash and forced me to manually shut down the computer. I did a print screen then pasted elsewhere.

I've just spent the last 10 minutes searching on my Lexia for any button to enable graphing sensor data and cannot find anything. I've checked the live sensor data on both Engine ECU and Gearbox ECU and there is no sign of a button that looks like a sinewave, so I can only assume that this functionality is not possible with the ECU's in a 98 Xantia. Pity...

What version of Lexia software are you running ? If you go into "Configure your Diagnostic Tool" -> "General Configuration" -> "Tool Configuration" you will see a screen with software and hardware versions. Mine says Lexia (500.44)

Does anyone know if this is the latest version, and has anyone else used the parameter graphing function before ? It would be SO useful if I could find a way to get that to work...

PS the save to disk button works fine for me - it captures a snapshot of the data on the screen for later access. The snapshots are accessed from "Consult stored data" -> "View memorised parameter measurements" -> "Standard parameter measurements".

[Mandrake]

By the way, do you get those diagrams from the Citroen service box DVDs or from logging in to their website? I found them for download "elsewhere", is this free information or an illegal download?

Its from the Citroen Service box DVD's, yes.

Technically, I'm sure its an illegal download, but then so too are the cloned Lexia's, as the software has to be patched/hacked to work with the clone interfaces, and to get around the software activation.

The way I look at it is that we do what we have to do to keep our cars working when they get to an age where the manufacturer no longer cares about supporting them. In the days before computers and electronic manuals, we might have photocopied an official service manual from a friend in the trade (also technically illegal) because they weren't readily if at all available to the general public and those outside the trade or dealerships.

Electronic manuals and ECU's requiring proprietary diagnostics tools to configure and diagnose them have upped the stakes a bit and made it a lot more difficult for the home handyman to maintain a car, so getting hold of technical documentation and diagnostic software has become a lot more essential to maintaining a car on your own...so although technically illegal I don't see it as being fundamentally any different to photocopying a printed manual.

[pcspinheiro]

I will check what version I have (the DVD had V47 written on it. There was an update to V49 in there, I think, but I did not bother installing it). I will also trace what steps I followed to get the plotting of the data but I need time to do this connected to the car. This weekend at the latest.

FYI, it does not "plot as you go" but instead records data and when you press stop it displays it. Still very useful, I think!

Cheers!

[pcspinheiro]

Hi again and sorry for taking so long to reply, but time is what I currently miss the most...

Here's how I do it:

Go to diagnosis>test by function>power unit>Engine>Injection>parameter measurement>personalized parameter measurement

then, once you select what you want to display (up to 6) the graphing button should appear (engine may need to be turned on). I forgot to check the software version...

Concerning my problem, I could not find a strict relation between any parameter and the changing in engine RPM... The idle valve position did oscillate a bit but that did not always match the RPM, the intake manifold pressure followed the RPM surges better but I guess that could a a consequence and not a cause... Therefore I initialized the adaptive learning and followed instructions but the low idle persists...

I'll keep you posted if I find the fault and solution, but there was a logged error on the BSI about the wrong coolant temp being communicated...

[Mandrake]

Thanks for the tip on the graphing, I don't remember seeing the personalised parameter measurement option but I'll take another look.

Regarding the wrong coolant temperature fault logged by the BSI, was this before or after you disconnected the coolant temperature sensor ? It may have been logged at the point you unplugged the sensor.

Are you still seeing the incorrect coolant temperature on the Lexia live data from the engine ECU ? Try getting a reading first thing in the morning when the engine is totally cold and before starting it, at this point the reading should match ambient temperature and that of the inlet air temperature sensor within just a few degrees. What does the Lexia reading change to if you unplug the sensor ? (It should either go very high or very low)

If it still says 40-45 degrees with a cold non running engine your next step is to replace the coolant temperature sensor.

One other question - you say the BSI had logged a coolant temperature reading fault, is there a coolant temperature reading in the live data of the BSI that you can compare with the engine ECU reading ?

[pcspinheiro]

Good points you raise there! I will check the error codes again since I deleted all of them this time and then turned off the ignition, so any that appear should be recent. There was one thing that struck me when looking back at some data recorded simultaneously; the inlet air temp was reading 50 C when it was a mere 1 C outside! Sure, the engine was warmed up, but would that bring up the air temp to 50C on air constantly flowing through? There was no fault whatsoever related to that sensor. I could try to disconnect it and see what happens but I suppose if that sensor is telling the ECU that the intake air is very hot (therefore less dense) that could lead to a fuel/air unbalance. Don't know if that could explain my problem though...

I will just pick your brains with another thing while waiting on the results of playing with the intake air temp sensor; I get a lot of white smoke (looks like steam really) from the exhaust but this is more when the engine is also warm. I'm dreading a head gasket failure although I do not notice any coolant disappearing (at least not noticeably) or any mayo in the oil and do only drive short runs at a time so it could also be lots of water in the exhaust system that then turn to vapor when I accelerate harder. Any thoughts? I also did not see any discoloration in the spark plugs and, at least in my 2 months ownership, the engine doesn't overheat and the fans cut in when it's too warm bringing down the temp fast... however, I'm seriously considering getting one of those CO2 tests for the coolant to see if I can get some peace of mind...

thanks again

[Mandrake]

I've noticed the same thing with the air temperature inlet reading on my V6 - actual ambient temperature is barely above freezing but when the engine is fully warmed up the air inlet temperature is reported as around 40-45 degrees. It seems this reading is valid though because if the car is left overnight to completely cool the air inlet temperature reading (as well as the coolant temperature reading) are both within 1-2 degree C of the actual outside ambient temperature reported on the dashboard... so yes, it does seem that the inlet air is warmed a lot as it travels through the air intake system in a hot engine bay, so your reading of 50 is believable.

Just check both inlet air temperature and coolant temperature first thing in the morning after the car has rested for at least 12 hours and before the engine is started, and as long as both read very close to ambient conditions they are probably ok.

Regarding the smoke/steam, I also have the same "problem", it only seems to be an issue in very cold weather, about 5-6 degrees and below there is a lot of what looks like smoke/steam, however there is no lost coolant, the oil is fine, no smell of smoke, and I've been assured by others on the forum that its just condensation. The V6 certainly seems to put out a lot of it!!

If it doesn't do it in warmer temperatures it can't be smoke, as a faulty engine would smoke at any ambient temperature.

I posted the following video in another thread back in early October (around 5 degrees ambient temperature) showing the steam and was assured its normal in cold temperatures:

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Now that temperatures are in the -3 to +3 range its even more prominent and obvious than shown in the video. I also do lots of short trips so I suspect you have nothing to worry about, just lots of condensation in the exhaust system generating a lot of vapour, much like steam from your breath in the same conditions...

[pcspinheiro]

Cool, I'll check that as soon as possible. I will try to get a video of the steam and post here for opinions.

EDIT: I was fooling around with the Lexia this morning and did some actuator tests, the last of which was to the idle control valve. When I used the car again in the afternoon to pick up the kiddos it would start the engine then stall in 1 sec before I had time to do anything!!! I was beginning to think it would go nowhere but then I managed to keep the revs up a little with the gas pedal and went on, always keeping it revved up slightly above 1000 RPM; it was running quite rough. If careless when shifting the revs would drop to something like 300... Twice it stalled while shifting, dash lights went out, but it came back to life (no gear engaged!!! ). I was freaking out but on next start up after sitting parked for sometime it was running again, maybe better than usual. Maybe the ICV was left in the wrong position after the tests and the ECU would not acknowledge that? I just hope it doesn't happen when the misses is driving it, she would just abandon it in the middle of the road

Will try to check for stored fault codes...