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From: moray on 23 Aug 2008 15:57

"Derek" <derekhtodd(a)spamsmapspamyahoo.co.uk> wrote in message
news:g8p23o$q0p$1(a)energise.enta.net...
> Derek wrote:
>
>> Tim.. wrote:
>>
>>>
>>> "Derek" <derekhtodd(a)spamsmapspamyahoo.co.uk> wrote in message
>>> news:g8n18l$8tr$1(a)energise.enta.net...
>>>> Hi,
>>>>
>>>> Does anyone know if there is a low cost fault code reader for a 1998
>>>> Renault
>>>> Megane Scenic RT dTi 1.9 engine. It keeps going into 'limp' mode until
>>>> ecu is reset.
>>>
>>>
>>> when exactly does it enter LOS mode?
>>>
>>> Turbo actuators are sods on these- they over-boost then the ECU goes
>>> into
>>> LOS.
>>>
>>> Tim..
>>
>> Thanks to all who've replied so far.
>>
>> I'm tempted to go for the Argos one since if it doesn't work they'll take
>> it back - I didn't define what I meant by low cost - just not Renault's
>> full 'testbook' or whatever they call it! The 100 quid version seems to
>> be
>> a better buy as it does 'live' data?
>>
>> When I'm saying it goes to LOS, it has the symptoms of that (see below),
>> but no dash warning light (bulb is working!).
>>
>> I've been having a good look at things. The engine 'sounds' fine and
>> smooth - smooth is funny term for a Renault dTi but hopefully YKWIM!
>> Engine appears to be limited to just over 3000rpm, and under load runs
>> out
>> of breath before that - clearly no turbo happening. Last night removing
>> battery power for a while would restore normal engine behaviour, until
>> driven for a short while. It MAY well have been after some boost that
>> this
>> happened, but it now seems to be stuck in the 'limited' state.
>>
>> I'm trying to use Haynes 3395 for this, but it doesn't seem good for the
>> F9Q engine,in particular. I'm not seeing a lot of evidence of vacuum
>> activity within the engine, but the brakes seem fine, so am going to look
>> at this next. An intermittant problem doesn't suggest that a hose has
>> come
>> off, but I suppose there could be a split somewhere? The normal 'sigh'
>> noise you hear on switching off is not happening.
>>
>> Turbo actuator - I assume this is the wastegate actuator on the dTi? Is
>> it
>> vacuum powered via a solenoid? How would I test it (fault code reader?!)
>> Access looks a little awkward as it's round the back of the engine under
>> the dashboard - remove air hoses, I assume?
>>
>> Many thanks,
>>
>> Derek
>
> OK, no splits that I can find in the vacuum hoses. There is a large bore
> hose and a very small one coming from the camshaft driven vacuum pump. if
> I
> clamp the main hose with pliers, and remove the small hose (which goes to
> the EGR solenoid), I don't feel much if any vacuum when I block the small
> hose with my finger - should I? Haynes; "As a guide, after one minute, a
> minimum of 500 mm Hg should be recorded." at idle with a gauge on the main
> hose.
>
> Is it reasonable to conclude that the pump is the culprit, or could there
> be
> other explanations?

Likely.
With the engine running, you should feel noticable vacuum on the end of the
pipe from the pump, but a leaking brake servo could also be the cause.

Easiest way to check, is feel how much vacuum you get at the small pipe with
the servo connected, then disconnect the main pipe from the servo. Block the
big pipe with one finger, then feel how much vacuum you get on the small
pipe. If you get noticeably more on the small pipe, then the servo is the
culprit.

Of course, the proper way to check would be using a vacuum gauge.


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