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-   -   Flat Spot (http://www.autobanter.com/showthread.php?t=26023)

joe March 5th 05 12:52 PM

Flat Spot
 
Hi,

My car has developed an annoying flat spot at very low revs, just as you let
the clutch off it hesitates & then picks up this is around 850-950 rpm.

This makes for jerky or even stalling at pull away in stop start traffic,
unless you rev it to 1000rpm then its ok, if it was just that I might live
with it but there is another side to it that is really annoying.

As your going along in traffic at about 40mph if you ease off the
accelerator a bit & then the traffic speeds up & you push the accelerator
(softly or hard) the car stumbles like a kangaroo stutter which is driving
me mad.
Now before I give money away I want to know this, could a re map of the ECU
fix this problem?

The reason I'm being so cautious is that I phoned up 2 separate BMW
Independents & ,without seeing the car, they told me it would need the
Dual-Mass Flywheel changing & it was not a flat spot!??!!

I then took the car to another Independent & he has told me its definitely
NOT the flywheel,he in fact laughed out loud when I told him what had been
said, it was in fact a fuelling problem, coupled with (excuse the Pun) there
is some wear in the Prop exaggerating the flat spot.

So I thought I'll have the Prop overhauled & have the ECU Re mapped , but
will they be able to stop this ??

THANKS IN ADVANCE FOR SOME KNOWLEDGEABLE IN PUT
JOE



keith March 5th 05 01:56 PM

"joe" > wrote:

>Hi,
>
>My car has developed an annoying flat spot at very low revs, just as you let
>the clutch off it hesitates & then picks up this is around 850-950 rpm.

- snip stuff
>
>I then took the car to another Independent & he has told me its definitely
>NOT the flywheel,he in fact laughed out loud when I told him what had been
>said, it was in fact a fuelling problem, coupled with (excuse the Pun) there
>is some wear in the Prop exaggerating the flat spot.


i traced my "prop wear" to a worn outer CV joint. I could hear a
slight clunk as i engaged first, from stopped. In my case that would
be the clutch drag too!

I have heard that the flexible coupling or guibo (between prop-shaft
and gearbox) can also fail with age.. how old is your car?


keith


joe March 5th 05 07:14 PM

1994! I've contacted a local firm that rebuilds & balance's Props ,so if it
gets a bit warmer soon I'll take the Prop off & let them rebuild it .

There is a slight clunk from the middle of the car if you listen hard & drop
the clutch a bit quickly ,I've also realised now that at 60-70mph threes a
very slight vibration so its all pointing to the Prop , not cheap but at
least its not as serious\Expensive as the BMW garages made out.

I had a clutch kit fitted 66,000 miles back when it had to have a
replacement engine, the clutch is so light & smooth , these garages only
lose custom & get a bad name by all this lying.
"keith" > wrote in message
...
> "joe" > wrote:
>
> >Hi,
> >
> >My car has developed an annoying flat spot at very low revs, just as you

let
> >the clutch off it hesitates & then picks up this is around 850-950 rpm.

> - snip stuff
> >
> >I then took the car to another Independent & he has told me its

definitely
> >NOT the flywheel,he in fact laughed out loud when I told him what had

been
> >said, it was in fact a fuelling problem, coupled with (excuse the Pun)

there
> >is some wear in the Prop exaggerating the flat spot.

>
> i traced my "prop wear" to a worn outer CV joint. I could hear a
> slight clunk as i engaged first, from stopped. In my case that would
> be the clutch drag too!
>
> I have heard that the flexible coupling or guibo (between prop-shaft
> and gearbox) can also fail with age.. how old is your car?
>
>
> keith
>




[email protected] March 7th 05 02:58 PM


joe wrote:
> 1994! I've contacted a local firm that rebuilds & balance's Props ,so

if it
> gets a bit warmer soon I'll take the Prop off & let them rebuild it .
>
>


If indeed it is the prop it might just be the rubber guibo. I don't
know how much work it is to replace the centre bearing but I'd guess
not much. The prop should come balanced from the factory. It could be
the flywheel though, at least in part. ...or engine mounts or similar.

On another car I have a garage diagnosed a "missing centre bearing" and
quoted UKP 325 (~US600) for a recon propshaft. Actually it was just
the rubber bearing support that had degraded and cost UKP 15 for a new
one. In fact, all that's there right now is a loop of old fuel pipe.



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