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My HDi is hunting when you start the engine from cold sometimes aggresively. Its my dads one. Its been like that for a long time but now that its mine, i want to get it sorted. I think its the high pressure pump. Can these be fixed or will I replace them. If it needs to be replaced can anyone recommend a good site? Or will I make a trip to the scrappys?

can you explain a little more. when you say hunting are the revs going up
and down or is the tickover permanantly high ???

Apologies. Revving between 850 and 1050 revs at less that 1 second intervals. So, basically its like the engine is vibrating really aggressively. Since its a diesel its loud and annoying. When I set off the revs are still unstable until such time as the engine warms up, then its fine. However, if i turn off the engine and turn it on again while the car is warm, it hunts. This can be resolved by a quick tap of the throttle. This only works when warm. When cold, its loud and agressive all through the gears until it warms up again. Extremely annonying I tell thee

Total ignorance: Does the throttle position sensor have a switch in it to tell the ecu it's meant to be idling?

Oops, read your last post properly this time. Just thinking aloud there

Can I have two more guesses? The pressure regulator or whatever it is that actually controls the air flow (I've no idea what!).

I think you're going to have to get a proper diagnosis done here I'm afraid, go for something with "Bosch Service" written on it and avoid anything with a picture of a lion...

Surely if it was the fuel pump, you'd have issues while driving? I'd rule out the TPS too as that would more likely cause stalling and irregular idling. Sounds to me like the idle control valve/solenoid is iffy and unable to hold the throttle open. Try cleaning it?

steve_earwig wrote:Total ignorance: Does the throttle position sensor have a switch in it to tell the ecu it's meant to be idling?

Nah the TPS is a simple variable resistor, like the volume control on an old stereo. 12v goes in one side, and somewhere between 0v and 12v comes out based on how open the throttle is

And the fourth wire is for..? Hold on, dur silly me, I'm looking at Haynes

have a read of this it might be worth a try

viewtopic.php?f=1&t=4815&p=47026&hilit= ... ter#p47026

Well. I can rule out the throttle body, the AFM, the air filter. My uncle the mechanic told me that the HDi's have two fuel pumps. A low pressure one in the tank and a high pressure on up front. The high pressure one is at fault and is sending inadequate amounts of fuel to the injectors intermittently. But when it warms up its ok again. New High pressure pump is needed. On eBay they only have water pumps and tank pumps with sender units. I'll get it sorted though.

I found out something cool today!!!!!!
When you hold down the CD button on the Stereo it goes into shuffle mode!!!!!!!!!!!!!!!!

That could apply for when it does it when it's cold but the bit where it does it hot until you blip the throttle? If it's sending low pressure intermittently wouldn't have a more pronounced effect when you're accelerating? Maybe it is the high pressure pump giving you all these problems (and I'm hoping for a post where you say it fixed it) but I reckon you should get the fuel pressure measured before you start forking out cash! I have a feeling the HP pump takes a lot of setting up too.

The HP pump should deliver a solid 298 Bar at idle - I mean every HDi on the road should read the same unless the pump's failing.

Have a scout around in this place you may it quite helpful http://www.ilexa.co.uk/forum/index.php/board,22.0.html

Did you resolve this issue? My V6 does the same but it also does it ocassionally during normal driving which is a bit worrying cos it could accelerate into the car in front!
Would appreciate new advice. Thanks

I'm not exactly sure but it's very unlikely to be the same sort of thing that affects a diesel. As I'm sure you know, the Haynes for the 406s doesn't cover the V6, so I'm not sure of the set up. There are a couple of owners on here so maybe they'll be along with some suggestions, there's also the 406 Koupe Klub (http://www.peugeot406coupe.com) where there's lots of V6s so probably well worth a search. What have you looked at so far?

Thought for the day: Lambda sensor.

Thanks for that, will check out the coupe site. Haven't done anything yet, under the bonnet looks like something from outer space, it's enough to be able to top up the various reservoirs! Cheers Sheila

she3x406 wrote:Did you resolve this issue? My V6 does the same but it also does it ocassionally during normal driving which is a bit worrying cos it could accelerate into the car in front!
Would appreciate new advice. Thanks

Give the idle control valve a good old clean out with carb cleaner. Not looked for it on the V6, but it should be a metal cylinder in-between the throttle body and the air box (connected to the small pipe coming out of the back). Give the pipe a good clean too, and the throttle body, and of course it never hurts to replace the air filter and give the air box a good clean