406oc.co.uk

I thought the 406 was running a bit better with the new fuel filter housing, but its back.

Basically it feels like the hdi is hesitating at low revs, 1800rpm or so. Almost like either a small misfire, or the turbo isn't spooling.

Thought it was the fuel pump, but no metal shavings in the old fuel filter...
Air filter was also replaced, the old one was dirty.
Ran some redex gold injector cleaner through it last tank, but hasn't helped.

Read somewhere that the EGR might need cleaned, or some sort of turbo solenoid might need replaced?

I'm also finding it difficult to perform a smooth gearchange, as without throttle the engine feels like it is labouring, but with a touch of throttle after changing gear, especially 3rd to 4th, the car lurches slightly. Maybe I need to change my driving style (last car was a GTV).

Cleaned the MAF, made no difference at all.

From what I have searched, it seems like a common problem across the PSA HDi cars and vans, yet there doesn't seem to be one definitive answer.

A few people have pointed towards the EGR, so that will be my next try.

The code reader didn't throw up anything useful btw.

Symptoms are what feels like misfire / hesitation at 1500-1800rpm, and the car feels like it should be driven in a lower gear eg 3rd at 30mph. Difficult to drive smoothly.

I would maybe check / consider the following mate:

air leak at breather hoses / intake

injector rail pressure sensor

fly by wire throttle unit

it seems the ecu is not delivering the correct fuel pressure at those particular revs...

FlySpeck wrote:I would maybe check / consider the following mate:

air leak at breather hoses / intake

injector rail pressure sensor

fly by wire throttle unit

it seems the ecu is not delivering the correct fuel pressure at those particular revs...

Thanks that gives me some more pointers.

I would have thought that if a sensor had went the ECU would have thrown a code or 2 about it or show the engine light (as I noticed when I forgot to plug the MAF back in )

It definitely feels like 1500-1800 it's not getting enough air or something, because it picks up towards 2000.
And at "normal" gearing eg. 4th at 30mph, it feels a bit laboured.

You'd really need to see the live rail pressure to see what's going on, I don't think many HDi'ers would say this is 'normal'.

You could speak to a Peugeot dealer for a 'Global Test' - about £60.00 but pretty thorough. Some independants struggle to get usefull data off of these cars unless they've got really good equipment ££££££

saying that then, how long have you had the car? I have only had mine for a couple o weeks but the turbo makes no useful boost till 2000 so in 4th at 30 mine is dour too. I think the hdi turbo is the size of a tangerine and theres no intercooler on the 90.

I would buy an £80 tuning box off evilbay and that will whack it up to 115bhp, a very useful lift.

FlySpeck wrote:saying that then, how long have you had the car? I have only had mine for a couple o weeks but the turbo makes no useful boost till 2000 so in 4th at 30 mine is dour too. I think the hdi turbo is the size of a tangerine and theres no intercooler on the 90.

I would buy an £80 tuning box off evilbay and that will whack it up to 115bhp, a very useful lift.

I've had the car a few months. I've noticed the turbo boost at 2000.
It isn't so much that, it's that it drives ok from 0 - 1500rpm, then it feels like its not getting enough air/fuel, then at 1800rpm it lurches slightly almost like a misfire, picks up a bit then it drives a bit better. It just feels a bit lumpy.
Changing gears also causes it to lurch a bit sometimes, hoping the clutch isnt going.

It is most noticable this phenomena at that rev band 1500-1800.

It just doesn't run as smoothly as my old XUD / Turbo-XUD Citroen diesels, which is a bit of a disappointment.

I know it's not the quickest diesel of the mark, wanted to get the 90bhp baseline running perfectly, then was going to look into tuning boxes. Are those £80 ones half decent in your opinion?

sirwiggum wrote:It definitely feels like 1500-1800 it's not getting enough air or something, because it picks up towards 2000.
And at "normal" gearing eg. 4th at 30mph, it feels a bit laboured.

Dont rule out the MAF just yet. It sounds like it still could be the issue. If you pick one up in a scrappy, you'll know for sure. They're 20 quid or so second hand. I did the same with my HDi and it was the MAF. Check your throttle body and make sure there is no slack with the accelerator cable. It should be tense enough. I dont think there is a problem with your gearbox. The pug gearboxes are a bit notchier than in alfas. My mate said changing gear in a 406 is like stirring porridge

FlySpeck wrote:I would buy an £80 tuning box off evilbay and that will whack it up to 115bhp, a very useful lift.

I think the consensus on here is that a remap is the way to go rather than tuning boxes who fool ECU's and eventually ruin engines.

Welly wrote:You'd really need to see the live rail pressure to see what's going on, I don't think many HDi'ers would say this is 'normal'.

You could speak to a Peugeot dealer for a 'Global Test' - about £60.00 but pretty thorough. Some independants struggle to get usefull data off of these cars unless they've got really good equipment ££££££

Thanks I'll ring round the local Pug stealers for a diag. Global Test. :thumbs:

eoin27 wrote:

sirwiggum wrote:It definitely feels like 1500-1800 it's not getting enough air or something, because it picks up towards 2000.
And at "normal" gearing eg. 4th at 30mph, it feels a bit laboured.

Dont rule out the MAF just yet. It sounds like it still could be the issue. If you pick one up in a scrappy, you'll know for sure. They're 20 quid or so second hand. I did the same with my HDi and it was the MAF. Check your throttle body and make sure there is no slack with the accelerator cable. It should be tense enough. I dont think there is a problem with your gearbox. The pug gearboxes are a bit notchier than in alfas. My mate said changing gear in a 406 is like stirring porridge

FlySpeck wrote:I would buy an £80 tuning box off evilbay and that will whack it up to 115bhp, a very useful lift.

I think the consensus on here is that a remap is the way to go rather than tuning boxes who fool ECU's and eventually ruin engines.

I'll maybe try another MAF, I'll get onto Traynors and see what they have.
Accelerator cable was slightly slack, though I then adjusted the pin too much and it became worse to drive, have put the pin where the cable is now just tight enough and drivable.

Yea the gearbox isn't quite as tight as the GTVs was. Though it was noticable the other way coming from a Xantia before that too!
Was half expecting it going back to the PSA stable.

There was another thread at the weekend about tuning boxes, that a remap is advised. Theres a local firm will do it for a few hundred, so if I could get the baseline 90bhp running well, I will consider this to allow safer overtaking etc.

Thanks for your input! Appreciate it!

well obviously a remap is (or should be) specifically tweaked to suit the torque map and airflow characteristics of the exact car, but at the end of the day they can only increase the injection pressure on a diesel.

diesel tuning boxes dont and cant ruin an ecu, thats daft. they just apply a blanket fuel pressure increase offset over and above the value sent from the ecu to the rail pressure sensor / regulator. Its the old "IAT resistor" power boost crap that are used on petrol cars to fool the ecu into injecting on the cold enrichment map that can cause problems.

the boxes come with factory plugs and are supposed to be set to as close to a remap as possible, and i know id rather spend £80 than £300 to get nearly the same result on a 10 year old work horse but its a personal choice.

I don't have much experience of remaps or anything. From my pocket's point of view, the £80 box is definitely preferable. Like you say, on a commuting car.
I was scared by previous comments that compared them to the resistor-in-a-box. Would like to get the engine sorted and then see about increasing the overtaking power a bit

Regarding the MAF replacement - Is it worth doing a soft reboot of the ECU to get it to pick up the MAF and to kick off the learning algorithms? (idle, town run then an italian tuneup?)

Cheers!

Disconnected the EGR by the blue plug and it made no difference.
I will see what the new MAF does the I'll drop it in to Pug dealer for the diag test.
Cheers.

the maf may be at fault and only testing or replacement will show it up.

you may find an ecu reset works but if the maf is faulty still, it wont change. sometimes they can get wet if you hit a big puddle and will act up until the electronics dried out (happened to me) but grabbing a cheap one off a scrapper would be a good way to go.

I would say that before you visit a garage for a diagnosis then it would be worth checking all the wiring to sensors *really* well to check for wear, splits, shorts etc just in case it's a simple wiring fault. It would even be worth checking the look of the massive multi-pin plug on the ECU (although I could never get mine off and daren't pull it too hard) but on some cars the pins can corrode a bit and cuase intermittant problems. Always disconnect the battery for a while before messing with anything important.