406 Exec 2.0l Idling Rough/Chunky

Hi, I have recently bought a 2000 406 Exec 2.0l which is a beautiful car
and is very tidy (it was the natural replacement for my trusty 405 auto
that was recently a right off after 6.5 years). However it is not as
smooth as it should be. Sometimes (but not always) the car has a rather
rough idle which makes it feel like a diesel, it also seems sometimes to
surge and drop back in power when driving. A friend describes it as a bit
chunky.
I have had it tuned and the chap was mystified by it. Apparently the ECU
readings are all spot on, his thoughts were firstly a dirty fuel injector,
or secondly the timing belt is out or lastly but doubtfully it needs a new
coil pack.

I have since run through slick 50 fuel cleaner twice and have added slick
50 engine treatment to the oil. I have had the fuel filter replaced by my
local garage and his thoughts were a sticky rocker. Since then I have
MOTed the car at the same garage so the emmisions etc are all alright. I
find it hard to believe the timing belt is out (though I think that the
prev owner had this changed at the last service) as surely it would have
much more severe effect if this is the case. Don't want waste money on a
new coil pack on a whim - has anyone got any ideas?

Thanks in advance
Euan

 

i have an 1800cc, and sometimes it happens to me, but it soon goes away and
it all settles down. i know its a little worrying and disconcerting though.
one time it was because i had put a few revs on it; i had my foot resting on
the throttle inadvertantly, didnt even realise, any way then i switched it
off. Because its an auto choke the next morning it was a bit rough, and my
daughter waiting outside the lock up said she could smell petrol, it was
flooded. Yes i know what the problem was; maybe its a fuel
distribution/carburetion fault!?
just a thought, it might spark the thought trains a bit.
regards, Mark.

 

.. Don't want waste money on a

Likely as not is the coil within the injectors because I had all that done.
Still no joy like a bag of potatoes on a cold start took it to a dealer,
couldn't find a thing on the diagnostic. Next morning he tried it on a cold
start, yep bag of *****. stripped the injectors found a damaged "coil".
Replaced said part, works a treat

 

Thanks guys
I guess I have been putting the foot down quite a bit so Taking heed to
Marks comments I was much more sedate in my driving and I have to admit
the car wasn't idling like it has been. However John's suggestion seems
very viable - maybe I miss understood when I thought he was talking about
a new coil pack. So maybe it will be a trip to the dealers after all. Can
you remember how much this cost you John to give me an idea what to
expect.
Thanks again
Euan

 

I'll have to check back but I think it was around the £200. 00 mark but that
does include the VAT. But do make sure that they test it COLD ie they've had
it over night and HAVE to start it cold. If it's the price is any different
I'll post again.

 

Well it has taken a long time to sort this one out but apparently the
problem was the Oxygen Sensor and I have now had this replaced for about
£200 and things seem to be much better. Not perfect but I think this is
possibly the injectors are dirty/clogged as it has been running rich for
so long. Euan