407 very intermittent surging

[EDC5]

Vehicles with CC and auto boxes can seem to behave oddly if the box changes gear while the CC is attempting to put on speed. Have noticed that some Inj-ECU-operated CCs will call for "full throttle" if CC is resumed with it set to a much higher speed - the car can be in quite a hurry to achieve the higher speed. If an auto box is in the mix too, it can get quite exciting!

On my X7, the engine ECU and the AM6 seem very well integrated. when resuming a much higher set point, the gearbox will kick down one or even two gears (if on a steep hill) without any excessive revs. I suspect the engine ECU can forewarn the AM6 what it's intentions are.

As an aside, when accelerating hard and a gear change occurs, I assume the AM6 ECU can temporarily cut the throttle as it makes it's own gear change; as the revs don't surge but remain static until the next gear is fully engaged.
This is not something I experienced whilst driving a Peugeot 308 with the ETG6 gearbox; when it decided to change gear the revs shot up and it was up to me to lift off the throttle whenever it started changing gears.

[moizeau]

Thanks for the replies. The speedo behaves itself impeccably. The first time, just before the surging occurred it had accelerated very fast resuming a higher CC setting, Yesterday after it went back to normal following the surging, which happened following a brisk acceleration without CC (which wasn't at my right foot's request, and it didn't rev above 2.5K but changed gear like short shifting) I did select a gear manually and the surging continued. 5 sec of power, 5 secs of nothing ... repeat. It's only happened twice in over a 1000 miles, so yes Marc, very intermittent. Both times the surging disappeared after it had been allowed to stand in the naughty corner for a while switched off. Not sure what the vapour, smoke, steam was. Yesterday after I tried to recreate it, but couldn't, using severe revs, manually and automatically in 34 deg ambient, no issues with the v/s/s. I've never seen the engine temp go above about 93 in any driving condition
Just charged the laptop up, so I'm off for a drive.
Thanks all so far

[white exec]

Vapour/smoke/... Possible that there's some stray oil getting into the air intake (? turbo) intermittently, and the engine is surging while it consumes this? Have a look in the intercooler and intake pipework. Breather....turbo....
Rather like intermittent and v.short duration runaway...?

[moizeau]

No issues what so ever, no faults, nothing. I'm half pleased, but half not. I'll have a look at the intakes Chris, thanks. I would expect any oil drinking to cause high revs permanently until it's been consumed, unless the 'puter sees that the revs are too high and closes something down? Also when the surging occurred I booted it to see if it would clear? No. The surging, I forgot to mention, only raises the revs to 1800 then drops them to 500, repeat. It's fine at the moment and has only done this twice.
Cheers

[moizeau]

Just had a look Chris, the large pipe coming from the top of the intercooler going into the plenum is very clean. The one just below it going down into the depths is a bit of an oily beast, though the oil isn't visible from above. I only found it trying to find the screenwash cap that fell off and is currently hiding on the undertray.

[moizeau]

Next chapter... did it again today at 60mph in 6th, so I manually selected 6th on Chris's advice. This time the surging was far less. The engine sounded as if the clutch was slipping or it had dropped down a gear. It would sound like this for 5 secs then go back to normal for anywhere up to a minute. It did it it 4 or 5 times then cured itself! When I got home I plugged the 'puter in without switching the engine off.....and it's given me 3 codes. All within the injector ecu.

First..U1118 Communication comfort LAN
From...Distant
No communication with BSI-intermittant

Second..P1693 Remote control ECU wakeup
Start or stop request invalid-intermittant

Third..U2001 Main wake up request missing or invalid-intermittant

Any advice very gratefully received

[moizeau]

Done some surfing on other sites and there seems to be a multitude of possibles relating to these codes as well as the surging.

Water ingress in fuse box? Looks nice and dry.

Below par battery? Turns over and starts very well but does go into eco mode quite quickly...15 mins. I have a new battery on the BX which I bought 2 months ago and over specced the battery so it would be good for the 407. I can swap them? The BX won't care. Is the method of battery changing with BSI reset - Leave for 5 mins after opening the drivers window the switching off, change battery, turn on side lights?

Plastic air doser valve?

Sticky EGR? Would this have also caused the smoke from the rear of the engine bay that I saw once?

Sorry for so many questions but all my knowledge of cars is old school and this is a steep learning curve.

[white exec]

Wonder whether the apparent shifting down a gear could be torque converter lock-up coming and going? It would sound similar. Not sure whether t/c lock-up only occurs in top gear...?
Sorry I can't help with the fault codes.
BTW, how is the fluid level in the box?

[moizeau]

Cheers for the response Chris, I was just reading the oil change thread when I noticed the notification. I have 7 litres of JW3309 waiting for me in my workshop. I'm going to plug the diag in and familiarise myself with the relevant gearbox pages first. The cars done 167000 on original oil!

[EDC5]

That's quite an incredible mileage on the original oil. My oil was black after 57k miles so it might be in very poor condition after that mileage.

Does this surging only happen during hard (or moderate) acceleration; could the lock up clutch be worn to the point where it cannot grip hard enough so it slips.

Potentially the oil may be in such bad shape that the gearbox oil pressure cant be maintained high enough for lock up to occur fully?

[moizeau]

Cheers EDC5, it's only gone into 'surge mode' 3 times, the first time was after hard acceleration until it it the CC speed then surged, the second time at very low speed in, I think third gear, and yesterday whilst cruising at 60mph in top. Just checked the oil change thread (several times) and found the relevant pages in Diag. Am I right in saying:
1 - Run engine until g/box hits 58 to 68 degs
2 - Turn off engine and remove drain plug (drains about 3 litres)
3 - Refit drain plug and fill with 3.5 litres
4 - Warm g/box oil to the same as before whilst going through the box
5 - Remove level plug and wait for the drip, drip
6 - Refit level plug
7 - In my case repeat above
8 - Reset counter
9 - In my case repeat again in a month but with only 1 change

Thanks again

[EDC5]

So it surges at a steady speed then, the revs rise but not the speed or the entire car accelerates during the surging. I'm trying to work out if the surging happens when the transmission is locked up or not.

Yeah that procedure is correct only you don't need to measure the temperature before the first drain; I took the car to get the gearbox oil as hot as possible for the first drain.

Also when you are checking the level if you don't get a good stream of oil before the drip-drip then there isn't enough oil in the box. Add 500ml and do it again.

I'd be interested to see the state of the oil when you drain it. Remember to take a pic

[moizeau]

It does alter the speed of the car, but the surge has varied from similar to 'boot it' for 5 seconds then nothing for 5 secs to yesterday when it was very gradual and it didn't alter the speed a great deal, equivalent of dropping down a gear (revs rose) but I confirmed it remained in 6th by manually selecting it. Off to citroen now to see how available the o ring and washer is. I have got a selection of oil friendly o rings from when I rebuilt the Epic pump.
Yes I will take a picture, I imagine very black, possibly burnt and very liquid.
Thanks for the confirmation of the change.

[moizeau]

One quick question EDC5, can you remember what size pipe fits in the filler hole? I can then pick up a bit of tubing to stick on the end of my funnel. Thanks

[EDC5]

you might be better off going to a Vauxhall dealership for the o ring and washer. If you've read my other post (AM6 oil change) I give the GM part numbers for that. (the Peugeot / Citroen dealers near me didn't want to bother ordering one in for me!)

Not sue about the pipe specifically but anything smallerthan 20mm O.D. should fit I reckon; maybe 15 to be safe?

It seems bizarre that the revs can rise yet the speed hardly change in a given gear; the only conclusion i can think of is that it's not locking up properly and the engine and gearbox are effectively decoupled for a brief moment.