Engine revs dropping when braking

[scfc_151]

I have a 2001 306 hdi with 217.000 miles

Intermittently I get the revs dropping to the point where it feels like it will stall when pulling up to a junction. 

If I take my foot off the brake when stationary and re-apply the revs return to normal.

I thought about a vacuum leam but cant find anything obvious.

Any help appreciated

[toseland]

vac leak wont be too obvious if it is indeed the issue.

the vac on these is supplied by a pump rather than manifold vacuum and I don't think the vac has any further input to the engine side of anything on the HDi.. will likely be corrected if I am wrong however.


Try this: When rolling on a CLEAR empty piece of road, get up to 30mph and then depress the clutch and immediately release the throttle pedal and idle..

if the revs die down below you know its not a braking issue but an issue when you release the engine to an unloaded idle state and that would point to another area.. TPS, MAF sensor etc

There is a clutch switch on these, it sits just at the top of the clutch pedal and is only clipped in gently.. the switch should be closed when the clutch is released and open when you depress the clutch. Might be worth a check.

do the revs drop below "normal" (about 900) and present the symptoms you described above?

are there any loose connections or wires around that could (under braking) be moved forming a worse connection ?

Have you had any work done on the MAF sensor recently?

[pug306driver]

clutch switch, thanks for the heads u[p on that one toseland, noted that in my note book.

don't want to shanghi this thread or muddy the waters, but does the ecu increase revs slightly when clutch is pressed when car is moving at above say 20mph, in expectation of a down ward gear change??  have noticed this happening, and easy to achieve with ecu control, or it may be my big feet!

[toseland]

clutch switch, thanks for the heads u[p on that one toseland, noted that in my note book.

don't want to shanghi this thread or muddy the waters, but does the ecu increase revs slightly when clutch is pressed when car is moving at above say 20mph, in expectation of a down ward gear change??  have noticed this happening, and easy to achieve with ecu control, or it may be my big feet!

Its some electronic unicorn magic that holds revs steady in an effort to make gearchanges more smooth on most HDis (haven't seen one without) and some of the other models. on cars fitted with Cruise, its one of the automatic disengage inputs, (as is braking) for the CC

I dunno if it does it on the HDi but I know some VAG models and other cars will restrict revs if the clutch is depressed to say 3250 or something to protect the engine, don't think Peugeot do this on our cars.

when you look at it you will see what I mean about it being clipped in, its a ribbed piece of tube that just slides into position via a little clip.. mine fell out and it was strange to drive to say the least.   clipped back in, engaged properly and it improved it markedly

[scfc_151]

Hi

Thanks for all the info. Theres a quiet road on my way home from work tonight so ill give it a go

[scfc_151]

vac leak wont be too obvious if it is indeed the issue.

the vac on these is supplied by a pump rather than manifold vacuum and I don't think the vac has any further input to the engine side of anything on the HDi.. will likely be corrected if I am wrong however.


Try this:  When rolling on a CLEAR empty piece of road,  get up to 30mph and then depress the clutch and immediately release the throttle pedal and idle..  

if the revs die down below you know its not a braking issue but an issue when you release the engine to an unloaded idle state and that would point to another area..  TPS, MAF sensor etc

There is a clutch switch on these,  it sits just at the top of the clutch pedal and is only clipped in gently.. the switch should be closed when the clutch is released and open when you depress the clutch. Might be worth a check.

do the revs drop below "normal" (about 900) and present the symptoms you described above?

are there any loose connections or wires around that could (under braking) be moved forming a worse connection ?

Have you had any work done on the MAF sensor recently?

Hi

I tried this the revs stayed as they should.

[toseland]

possibly a loose wire or connection or other electrical problem... wonder if something is pinching a fuel line?

[scfc_151]

possibly a loose wire or connection or other electrical problem...    wonder if something is pinching a fuel line?

I must admit I forgot to mention this happens during cold weather. 

Could it be lack of electrical power if the battery isnt 100%?

[toseland]

I dunno... I doubt it..

have you had any code readings? might be something there possibly, might even just be when the engine is cold if the temp sensor is not up to scratch..

[Ruan]

Would bet on fuel pressure regulator in the high pressure pump jamming.