Revs drop while braking - Page 2

Robbberd · 13th July 2012, 07:30

Quote:

Originally Posted by Jakg

Wierd issue, this...

If I'm cruising along, and pop it out of gear, and start to brake, the revs obviously fall off - but rather than fall to idle (~800 RPM), it falls a bit further (~600 RPM), which makes the engine quite harsh (akin to being on the edge of stalling).

Once the car stops, the revs stay at ~600 for half a second and then it returns to normal idle.

And all of this is while out of gear

Any ideas? Car idles fine, if I pop it out of gear but let it coast it idles properly as well.

Anybody ever get to the bottom of this , mines just started doing it yesterday ??????

weird ???

COLVERT · 13th July 2012, 07:40

I don't suppose you'll get an answer from the OP as he never did come back to tell us how he fixed the problem.
Maybe he ran out of brakes and had to use a tree to stop.

Colvert. ( Still plump for low vacuum though.

)

Robbberd · 13th July 2012, 07:50

hi , how would that be checked ?
bearing in mind in a numpty at mechanincs lol

stuartie007 · 13th July 2012, 07:51

I don't believe it's a vacuum/popping it out of gear related problem. My car has been doing this for months, I don't pop it out of gear. It happens when idling at lights etc or sitting In traffic, many days when I start the car it idles low too.... It should idle at 625rpm but sometimes drops to 575, as if it's going to stall, but it doesn't. Yet to find out why my car has been doing this. My under bonnet stop went a couple of months ago so the in tank pump is probably knackered too, could this be causing a fuelling issue?

Robbberd · 13th July 2012, 08:29

would , some injector cleaner etc etc help the issue , is it maf/map sensor related, egr is bypassed on mine too..

Jakg · 13th July 2012, 08:34

I read somewhere this was some ECU anti-stall thing.

I never "fixed" it

HarryM1BYT · 13th July 2012, 08:37

Quote:

Originally Posted by John Hutch

My son passed his test last year, and I was eventually banned from trying to teach him myself because things have changed since I passed my test (probably about 1960)
The main thing was that changing down when approaching lights etc is frowned upon - you are told to coast and brake, hence the probable reason behind the enquiry.
I was told that brake pads are cheaper to change than clutch or gearbox.
(I still go down the gears though!)

As you slow you are supposed to stay in gear, not press the clutch, just use the brake alone. At the last moment before the engine stalls, you press the clutch and select what ever gear you need, or neutral if coming to a complete stop.

I was originally taught to use the gearbox to slow too, I now use a mix of methods - which ever suits the occasion. Generally I don't need to use the brakes much at all, relying upon planning well ahead.

Robbberd · 13th July 2012, 09:23

Quote:

Originally Posted by HarryM1BYT

As you slow you are supposed to stay in gear, not press the clutch, just use the brake alone. At the last moment before the engine stalls, you press the clutch and select what ever gear you need, or neutral if coming to a complete stop.

I was originally taught to use the gearbox to slow too, I now use a mix of methods - which ever suits the occasion. Generally I don't need to use the brakes much at all, relying upon planning well ahead.

even doing it as you have described , in that last instant as you clutch/brake /come to a stop... the revs drop quite low ( anti stall as someone mentioned ???), so low you think it will stall , and then they rise back up to idle..You still have to clutch when stopping , there is no escaping that one.
it is a weird one...

Robbberd · 13th July 2012, 09:50

Quote:

Originally Posted by Jakg

I read somewhere this was some ECU anti-stall thing.

I never "fixed" it

hmm , whats causing it to stall though ???

Jakg · 13th July 2012, 09:56

I think it sees revs dropping, not in gear, clutch not full engaged, your going to stall and does "something".

I think.

13th July 2012, 07:40	#12
COLVERT This is my second home R75 Saloon. Join Date: Feb 2009 Location: France/or Devon. Posts: 14,003 Thanks: 3,851 Thanked 2,167 Times in 1,816 Posts	I don't suppose you'll get an answer from the OP as he never did come back to tell us how he fixed the problem. Maybe he ran out of brakes and had to use a tree to stop. Colvert. ( Still plump for low vacuum though. )

13th July 2012, 07:50	#13
Robbberd Loves to post MG ZT Join Date: Feb 2012 Location: Wrexham Posts: 407 Thanks: 64 Thanked 5 Times in 5 Posts	hi , how would that be checked ? bearing in mind in a numpty at mechanincs lol

13th July 2012, 07:51	#14
stuartie007 Newbie MG ZT+ CDTI 135 Join Date: Mar 2012 Location: Belfast Posts: 18 Thanks: 0 Thanked 0 Times in 0 Posts	I don't believe it's a vacuum/popping it out of gear related problem. My car has been doing this for months, I don't pop it out of gear. It happens when idling at lights etc or sitting In traffic, many days when I start the car it idles low too.... It should idle at 625rpm but sometimes drops to 575, as if it's going to stall, but it doesn't. Yet to find out why my car has been doing this. My under bonnet stop went a couple of months ago so the in tank pump is probably knackered too, could this be causing a fuelling issue?

13th July 2012, 08:29	#15
Robbberd Loves to post MG ZT Join Date: Feb 2012 Location: Wrexham Posts: 407 Thanks: 64 Thanked 5 Times in 5 Posts	would , some injector cleaner etc etc help the issue , is it maf/map sensor related, egr is bypassed on mine too..

13th July 2012, 08:34	#16
Jakg This is my second home N/A Join Date: Feb 2010 Location: Suffolk Posts: 6,867 Thanks: 0 Thanked 397 Times in 302 Posts	I read somewhere this was some ECU anti-stall thing. I never "fixed" it

13th July 2012, 09:56	#20
Jakg This is my second home N/A Join Date: Feb 2010 Location: Suffolk Posts: 6,867 Thanks: 0 Thanked 397 Times in 302 Posts	I think it sees revs dropping, not in gear, clutch not full engaged, your going to stall and does "something". I think.