Slow(er) diesel

[dragonface78]

My 406 110 HDi is quite noticably down on power and a fair bit on economy compared to my mate's identical Pug. Any ideas what the most likely culprit is? It starts fine and revs fine. No engine warning lights on the dash. Can't hear any of the whistling that would indicate a boost leak.

Cheers


Jim

[Invalid Boy]

Aha! Welcome to club406!

Your car will store an error code for this. Can be caused by one of a range of sensors- the air mass measuring device can fail, as can temp sensors and so can vacuum tubing (pennies to fix!) after all that the codes need erasing as the car will be in limp home mode.

Common rail diesels are highly strung compared to their forebears...

[hillbillyracer]

I've not had much to do with the HDI engines, but as IB said the airflow sensor would give these symptoms & they go all the time on other diesels. You only get a light coming on if it fails completely & they dont, they just send the wrong value back the ECU but still within it's operating range so no fault code or light.
My mate's Rover 25 TD did a few, often if you knocked the ignition of & back on as you drove it'd come right for a while.

[dragonface78]

Thanks for the responses. Will have a look at the vac tubing to start with. After that will get it on a diagnostics machine - will it have to go to a dealer or any independent garage??

[dragonface78]

Just re-read your post HB - if there's no fault code guess there's no point putting it on a diagnostics machine! Might have to swap some bits off my mate's car to see what effect that has.

[Popshot]

I have an MG ZS diesel and the MAF is a common goer on these too. It never shows up on any warning light. If you disconnect the MAF on an MG the car goes into a mode that makes a best guess at the fuelling instead of relying on the simply wrong reading it's been getting. If the car goes noticeably better without the MAF it's knackered. On an MG disconnecting it doesn't bring on any warning light either so no codes need clearing. Check the same is true of your car before trying it.

[Invalid Boy]

Just re-read your post HB - if there's no fault code guess there's no point putting it on a diagnostics machine! Might have to swap some bits off my mate's car to see what effect that has.

VW's PD cars see a code of 17564 generated by this and Colin (who I bought my 406 TD from) had fault codes on his 406 HDi from MAF failure. However, as Kev says some faults on some cars (even on OBDII) do not get logged fault codes for operational failure.

A cheapie fault code reader (~£30 on ebay) will indicate codes and reset the dash. Getting hooked up at the dealer usually costs at least double that for a one-off.

Do bear in mind that the code is nothing more than an indicator!

[dragonface78]

£30! Bargain! Still, swapping bits off my mate's car is free and as usual I'm skint!

Cheers

[dragonface78]

Unplugged the afm and it made no difference so bought one for £30 off eBay. Finally got it delivered and fitted the other day. Progress is now acceptable rather than painful and seems to be more economical.

Cheers for all the advice.

[Evodelta]

Do you really have a face like a dragon?