406hdi(90) losing power

[Blackbob]

Hello.. Although my first Pug was a 504 pickup, about 25yrs ago, I've only just discovered this forum, so much more informative than a Haynes manual! My problem is this.. From time to time my '99 406hdi(90) loses power completely, however unlike any of the other threads I can find on here the car doesn't grind to a halt, but stays at idle speed. As soon as you feel it 'die' you can (a) take your foot off the throttle then press it again, the engine will pick up as if nothing had happened; (b) press the throttle hard to the floor and it will also pick up again. though it doesn't seem as lively. (c) put the car into neutral and the engine doesn't stop, it just goes back to idle. I've tried 2 ex-scrappy throttle position sensors and checked for clean connections, but had kinda learned to live with it.. Until last week when it had a major tantrum, still starts/idles perfect but no power, only smoke, from reading here I reckon it may be wastegate/MAF/ cat, havent had time yet to find out. Turbo itself still ok though. Anyone any ideas if the two things are related? BTW the car's an ex-taxi, now at 264k and not using any oil, bought at auction (without MOT) for £280, more comfortable to drive than our Jag X-type and with more useful boot.. Was offered £50 for the 406 (while still running, and with 6 months MOT) by those people who Buy Any Car.. NO WAY!! Hope you guys can help get us back on the road again!

[highlander]

Was offered £50 for the 406 (while still running, and with 6 months MOT) by those people who Buy Any Car..

Eh? Those very same people quoted my '99 petrol 406 saloon as being worth £750. Didn't take them up on that though as I know I can get more for it privately when I do come to sell it on.

As for the problem you've got - throttle position sensor (TPS), possibly? I wouldn't have thought it's going into limp-home mode as that's normally accompanied by all sorts of warnings, and the 406 doesn't go out of limp-home mode when you stomp on the accelerator. One of the people on this forum who is actually knowledgeable about these things will come along in a minute and tell me why I'm wrong again but that's my initial guess and I'm sticking to it (I don't know much about cars)

Oh, and welcome, by the way!

[steve_earwig]

Hi BlackBob, welcome

hrottle position sensor

But he already replaced the tps. Twice. It wouldn't account for the smoke naiver.

I'm a bit reluctant to say anything as my diagnosis this week has been pants But a couple of points:

(c) put the car into neutral and the engine doesn't stop, it just goes back to idle.

Isn't that normal, or is that still with the throttle pedal down? Is it an automatic?

still starts/idles perfect but no power, only smoke

It doesn't rev at all now?

[highlander]

hrottle position sensor

But he already replaced the tps. Twice. It wouldn't account for the smoke naiver

My bad apparently my reading skills roughly equal my mechanical skills today!

[rwb]

air getting into fuel lines? (Or something causing fuel starvation)

[ianjoh]

I think it is the EGR causing your problems. It may not be fully stuck open but I certainly think it is not fully shut. Not easy to work on but blanking it off would be your best bet.
If it was air or a blockage causing a fluctuation in fuel rail pressure then the ecu would sense this and put it into limp mode.

[Blackbob]

Hmm thanks for your help you guys, given me food for thought! Don't think it's drawing air as there's no coughing, it just dies, until you either lift off the throttle or floor it. Gonna investigate tomorro, don't know much about EGR wotsit.. yet.. Can't see it managing to pull itself up onto ramps in its present state, got big jack tho

[stevie3]

Hi, Just looking at your losing power problem, my stepson has a (90) hdi on 99 plate he had similar problems to you and others on this site.
He went down the same route as a lot of people on here, air flow, throttle position, egr valve, etc ect. He went to a nice lad around the corner from him who hooked up his laptop with lastest software and it started throwing codes out which helped a bit but didnt solve the problem UNTIL he moved the the wiring loom and the throttle position values went daft. Turns out the loom had been chaffing and cut through a wire (earth) i believe to the throttle position sensor, this problem had been going on for 12 months or more especially when it was raining and many replaced parts but is now cured.

This may not be the problem with your car or many others on here with cutting out / losing power problems but a simple check of the visible parts of the loom especially on the left hand side as you look into the engine bay may shed some light on the problem. I own a 04 (110) 406 estate with 77000 on it and i checked ALL visible pipes and wires on it and found even at this early stage things were starting to rub and wear and ive had to make slight adjustments.
This is my first post as I have only just registered on this site also I am not am a mechanic but my stepson and I have owned several old pugs between us 405s/406s and a couple of 306s aswel so come across problems all the time. Good luck hope you sort it out. Steve.

[ianjoh]

I would second that.
I have had 3 faults caused by broken and chafed/shorted wires, if the power comes back due to lifting off the throttle quickly it could be because the engine movement has temporarily cured the fault.
I had a particular problem with surging when doing roundabouts ect that was caused by the loom shorting on a bracket at the top of the engine just before the ECU.
Under the battery tray is also worth a look - I will upload a photo if I can find it of mine laid bare ( the car that is )

[Blackbob]

Quick update.. May be tempting fate to say it but I seem to have sorted my car, with the help of the wise and intelligent people in the 406oc Looks like it was the EGR, pulled the little pipe off the diaphragm-looking-bitty and stuck it on a bolt conveniently sticking out of the bulkhead, and the car has run fine since. Your chafed-wiring theory does sound very plausible though, I never thought of that, was convinced problem was throttle cable, or sensor, or pedal.. Ok so I'm destroying the ozone layer by not using EGR, but I've not got any other bad habits PS I'd forgotten what a comfortable car the 406 is to drive, after using the wife's Corsa