HDI bad when cold

[mjb]

Hey guys, been a while. So so busy... :/

Had to ditch the wife's hdi136 C5 due to:

• an undiagnosed probably suspension failure causing the outsides of new tyres to wear to the wires in a couple of weeks
• the need for another 2 tyres
• a very temperamental suspension pump - likes to blow fuses
• need for new brake pipes all round
• probably discs+pads
• ANTIPOLLUTION F**OFF
• needs work on rear suspension
• the fact I hate it
• ...and so on

and we've got her a nice shiny new (2009, 163k) C5 X7 estate. Quite a few toys, 2.0 HDI 140 DW10BTED4. Very nice it is too! When warm...

When it's warm, it runs absolutely perfectly. Cold however, it takes a while to start, then it's bouncing around at an unsteady 1300rpm sounding like it's not firing on one pot. White smoke out the back, engine's bouncing around on the mounts (which'll probably need replacing after this is fixed). When cool, not cold, it starts right away, but occasionally misses.

Lexia says injector 1 is blocked when the engine's bouncing off the bonnet. Before I go buying an injector and likely paying someone to change it (at 163k I'm not expecting it to play nice), does anyone have any input? I can't think of anything other than a properly knackered injector that'd cause this...

Also, which one is number one when viewed from the front? Left or right?



I knew something was up with this thing - too cheap, and the guy had it all warmed up for us. Also the rear wash/wipe fires at random - going to empty the tank in no time until I get the COM2000 fixed. Guy said "it's automatic" <BULLSHIT ALARM ON>. Yeah. Figured I can sort the COM2000 without too much trouble, and worked out there's probably a cold running issue, but figured with it running so well when warm, it can't be too bad...

The ECU log shows it's had faults cleared over a number of diag sessions the last few months. Reckon the previous owner (bought it from a breaker/used car dealer, not the owner) spent a pretty penny diagnosing this, and didn't like the dealer's quotes on replacing the injector and COM2000 so decided to get shot of it

[Welly]

Hello mjb!!

I'm thinking leak-off test and live diag readings for injector correction and stuff?

But something that screams out at me for some reason is a wiring issue like a chafed wire or bad connector on the injector loom maybe.

Are you sure there's not a diesel leak over night?

Other than that it might be worth checking for things like crank sensor but that shouldn't be affected by temperature, well no electrical problem should really but: French....

Good luck with it though and I hope others can help further, been pretty quiet here of late.

[Doggy]

Hi Matt,

I think No. 1 is at the gearbox end but, on Bosch-equipped 406's at least, if you disconnect one injector plug then fire it up, you'll get an EML and an injector N open circuit message.

As welly says, looking at the injector correction values in live data should help. Values of +/- 1% or thereabouts indicate everything's OK, big correction values should point to the culprit, (or possibly the one that 'fired' before it).

As I understand it the ecu uses the cam and crank sensors to determine how much the engine accelerates after each main injection pulse. If one cylinder leads or lags the others the injection volume for that cylinder is 'corrected' by the indicated percentage.

A leak off test will also show up a faulty injector. If they get bad enough, the HP pump can't shift enough volume to start the engine, maybe it could affect idling too.

Injectors aren't always impossible to remove, I swapped the set in my first 406 fairly easily. I soaked the wells with WD40 for a week or so before trying. Don't know whether it helped, but mine came out easily.

[mjb]

But something that screams out at me for some reason is a wiring issue like a chafed wire or bad connector on the injector loom maybe.

These PSA cars are bloody good for noticing shorts or open circuits - I know from experience the ECU would absolutely report something electrically wrong there.

Are you sure there's not a diesel leak over night?

Certain. Apart from under the PAS reservoir (possible leak...), the engine is perfectly clean and dry.

I think No. 1 is at the gearbox end but, on Bosch-equipped 406's at least, if you disconnect one injector plug then fire it up, you'll get an EML and an injector N open circuit message.

Obvious, but I completely missed it. Thanks

As welly says, looking at the injector correction values in live data should help. Values of +/- 1% or thereabouts indicate everything's OK, big correction values should point to the culprit, (or possibly the one that 'fired' before it).

Doesn't actually report a value on injector 1 when this is happening but when warm, the values are pretty much zero

As I understand it the ecu uses the cam and crank sensors to determine how much the engine accelerates after each main injection pulse. If one cylinder leads or lags the others the injection volume for that cylinder is 'corrected' by the indicated percentage.

Makes sense. If it were a rotating sensor I could see that being an issue on one part of the rotation, but it's likely the same mechanism as ABS rings and crankshaft sensors, which would need a big chunk of steel to break to cause the ecu to report just one injector knackered, and it wouldn't suddenly rematerialise when warm

Biggest clue to reinforce it being an injector for me is the violent shaking, like it's not actually firing on one cylinder...

Injectors aren't always impossible to remove, I swapped the set in my first 406 fairly easily. I soaked the wells with WD40 for a week or so before trying. Don't know whether it helped, but mine came out easily.

Actually, I've looked at this thing and there's virtually no corrosion anywhere at all in the engine bay bar the engine block These might come out easily!

https://www.icloud.com/sharedalbum/#B09 ... 0B49135700

To do a leak-off test do I just pull the braided hoses from the injectors put new bits of pipe on going to bottles?


My BMW failed its MOT. I forgot to replace the locking wheel nuts I had removed with the non-locking jobbies I bought. That's it. No advisory again! Last year it passed first time too! Pretty good going for the only unmolested 540i manual estate in the country I never actually had a PSA car pass without failing first, even my beloved v811hae coupé

[Doggy]

To do a leak-off test do I just pull the braided hoses from the injectors put new bits of pipe on going to bottles?

Pretty much - looky here: viewtopic.php?f=1&t=14490&hilit=wobble