"stuttering" disco

got me confused, but I think I know where its headed.

Got the disco back after the camshaft change (not terribly worn, but job is
now done) and the airflow meter failure.

So yesterday, heading off to the wilds of salisbury, gave it a bit of stick
to join the M2,

nicely and cleanly up to 90.

and then i felt it. the stutter. well thats the only way i can describe it.
Everything felt fine, but at 70 its got a judder/stutter. Let off the
throttle, the stutter goes.

Arse I thought. Day out ruined. but we didnt overheat, so I kept going.
Then I thought, low on fuel.

So I filled up.

And the hiss from the fuel tank was somewhat impressive - never had it go on
for that long before - serious vacuum.

Anyways, full tank, no difference. 65mph onwards get the stutter.

Well, we then spent all afternoon and evening in lowrange, and had no
problems at all (down a bit on power) but no stutter.

As soon as we hit 65 again, stutter.

So i'm thinking

is it

a) the airflow meter that was put on, still isnt right and I need to get a
new/recon unit

b) an ecu/sensor issue

c) the vacuum that built up in the tank, even without the cap being screwed
on tight

any thoughts / similar experiences?

the only other thing of note is that when the camshaft was changed (I gave
up) they found the engine was somewhat silted up with crap - missed at least
30K's worth of servicing

Si

What about the ignition system? Had a few bouts of this kind of crap
which turned out to be ignition amp related (although a new ignition
amp on its own didn't actually properly sort it). If they aren't new
I'd slap a new coil, ign amp and probably plugs on it.

That said, I'd have thought ignition problems would be apparent at a
certain RPM, not a certain speed.

Does it stutter on hard acceleration only, or on part throttle as
well?

You can run with the fuel cap off for a bit to see if that is an
issue?

The ECU may have stored a code or two.

I'm assuming it's a V8 by the way you talk casually about 90 mph...

--
Tim Hobbs

"Tim Hobbs" <[email protected]> wrote in message
news:[email protected]...
> What about the ignition system? Had a few bouts of this kind of crap
> which turned out to be ignition amp related (although a new ignition
> amp on its own didn't actually properly sort it). If they aren't new
> I'd slap a new coil, ign amp and probably plugs on it.
>
> That said, I'd have thought ignition problems would be apparent at a
> certain RPM, not a certain speed.
>
> Does it stutter on hard acceleration only, or on part throttle as
> well?
>
> You can run with the fuel cap off for a bit to see if that is an
> issue?
>
> The ECU may have stored a code or two.
>
> I'm assuming it's a V8 by the way you talk casually about 90 mph...
>
> --
> Tim Hobbs

Hi Tim,

yup she's a v8 - how did you guess???

new plugs, leads, rotor arm, dizzy cap so far

Its really noticeable when accelerating, but its still there when holding a
speed.

Its defo a speed thing, which leads me to think ecu/sensors - cos all the
time we were in low range yesterday (ie under 35mph) there were no problems
at all, but the rpms were right up there.

I think the fuel cap thing is a red herring, but there is a definite issue
brewing vacuum wise there.

Si

....and Si K spake unto the tribes of Usenet, saying...

> Its defo a speed thing, which leads me to think ecu/sensors - cos all
> the time we were in low range yesterday (ie under 35mph) there were
> no problems at all, but the rpms were right up there.
>
> I think the fuel cap thing is a red herring, but there is a definite
> issue brewing vacuum wise there.
>
> Si

I'd be looking at fuel delivery first, from what you say. The times when it
is happening are when the demand for fuel is highest - high revs in low box
are unlikely to need as much gas, whereas 70-80 on the open road you are
flooring it. If you back off to 60 or so, does it go away?

Trial run with petrol cap off, check fuel filters, fuel pump pressure? Lots
it could be, but that's where I'd start looking.

Had exactly this problem on a motorbike, turned out to be a blob of dried
Simoniz in the breather hole in the filler cap.


--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)

On or around Sun, 4 Dec 2005 16:28:59 -0000, "Si K"
<[email protected]> enlightened us thusly:

>c) the vacuum that built up in the tank, even without the cap being screwed
>on tight

could well be. You need to check the tank breathers - IIRC, 4 of 'em linked
to a system of pipework that goes off upwards. Bet you find it's blocked.

There shouldn't be vacuum in the tank, period.

--
Austin Shackles. www.ddol-las.net my opinions are just that
"Plus ça change, plus c'est la même chose"
Alphonse Karr (1808 - 1890) Les Guêpes, Jan 1849

Had exactly the same problem on my range rover , spent a small fortune
replacing every bit of the ignition . it would only do it at a set
speed in top gear every other gear /speed was fine , felt like I was
driving over a rumble strip it would splutter and slowdown drop down a
gear and it would tale off no problems, back up to 55 same thing would
start again !
Luckily I got talking to a bloke who was V8 mad , he said it was the
airflow meter and I pointed out I had replaced that but there was still
no change he told me that this was quite common as the engine was a bit
old and the wiring was not as new so there may be more resistance in
the electrical system so it was over fuelling just a bit , and this
would only show after cruising in top gear as in lower gear the
throttle position is not as constant ie in 4 you would spend more than
60 sec in one point .

So how do you fix it ? well what id did was ( he said he had don this
many times ! ) to take the top off the airflow meter mark up were
everything was , and take the readings of the resistance of the arm
across the variable resister , once this is done identify the wires
that the voltage is sent to the variable resister arm .

Ok this is the bit where you have to have a bit of faith ! go to
maplins and buy a 10 k varialbel pot one with a shaft on like a volume
control then on the airflow meter readjust the variable resister arm
so the resistance is slightly lower ( cant remember exactly how much
lower I set it , but I think it was less than 10 K ohms )
Cut the wire that is connected to the wiper arm on the loom and
connect the pot between the wires with enough wire to go back to the
drivers seat .

Take it for a run and get it up to speed , it will be a bit rough to
start but if you fiddle with the pot that you now have inside the car
you will be able to get it running well , small adjustments are best
and give it time to settle down between tweaks.

Once its running fine park up and using a meter read the resistance
across the pot AND the airflow meter , you should now be able to remove
the pot join the wires back together and set the position of the wiper
arm in the air flow meter using the reading you had when the pot was in
place !

got the old rangie runnig like a dream useing this method !

hope this helps

itcosthowmuch????? wrote:

> Ok this is the bit where you have to have a bit of faith ! go to
> maplins and buy a 10 k varialbel pot one with a shaft on like a volume
> control then on the airflow meter readjust the variable resister arm
> so the resistance is slightly lower ( cant remember exactly how much
> lower I set it , but I think it was less than 10 K ohms )
> Cut the wire that is connected to the wiper arm on the loom and
> connect the pot between the wires with enough wire to go back to the
> drivers seat .

Bloody clever. Make sure the pot you get is LINEAR tracked and NOT a
volume control, which are Logarithmic tracks. A Maplindroid is unlikely
to know the difference.

Steve

"itcosthowmuch?????" <[email protected]> wrote in message
news:[email protected]...
> Had exactly the same problem on my range rover , spent a small fortune
> replacing every bit of the ignition . it would only do it at a set
> speed in top gear every other gear /speed was fine , felt like I was
> driving over a rumble strip it would splutter and slowdown drop down a
> gear and it would tale off no problems, back up to 55 same thing would
> start again !
> Luckily I got talking to a bloke who was V8 mad , he said it was the
> airflow meter and I pointed out I had replaced that but there was still
> no change he told me that this was quite common as the engine was a bit
> old and the wiring was not as new so there may be more resistance in
> the electrical system so it was over fuelling just a bit , and this
> would only show after cruising in top gear as in lower gear the
> throttle position is not as constant ie in 4 you would spend more than
> 60 sec in one point .
>
<snip>

ah interesting - it had to have the airflow meter changed to get it going
after the failure last week. I've got to get a new meter, as the one on it
belongs to Dakar Cars till i get a new one.

will get new meter, then try your method

cheers

Si

On Mon, 05 Dec 2005 18:28:02 +0000, Steve wrote:

> Bloody clever.

Sneaky but I can't help thinking it's a cure without touching the real
cause of the problem, a high resistance connection somewhere.

> Make sure the pot you get is LINEAR tracked and NOT a volume
> control, which are Logarithmic tracks. A Maplindroid is unlikely
> to know the difference.

Not relevant as you are measuring the resistance after you have
empiricaly tweaked the pot under test. A log pot might make adjustment
slightly trickier if it happens to be at the "wrong" end of the pots
rotation. In which case swap the fixed end wire to the other end of
the pot...

--
Cheers [email protected]
Dave. pam is missing e-mail