3.9V8 roughness
Austin Shackles
"new toy" is a bit iffy about cold starting: fires easy enough but drops
back to below idle speed and stalls when stone cold.
once it's run for a bit to get warm (not up to running temp) it idles OK,
although return-to-idle still drops below idle revs for a few seconds and
then comes back up.
It's also slightly rough at certain rev/load conditions, most obvious is
pulling off with not much boot. Not as smooth as I'd expect. better when
it's up to temp, and it seems to pull OK if you give it some welly.
It is of course a 2-cat one, being a '95/96 model - so I'm not fully au fait
with how the system works. I presume that initially, the system uses some
default values until the lambda sensors are up to temp and working?
I'm thinking it might be mixture.
Any thoughts? I'll be looking at the plugs and likely replace them unless
they look very good, and I'll alos fire it up in the dark and look for
arcing in the leads, although they look quite good 8mm silicone ones,
they're not original. ditto air cleaner element.
It's been standing quite a while, apparently - they got new motors a bit
back and kept the discos as spares for several months - so it was MOTed in
march and has done about 7 miles since. This may or may not be relevant -
and it may settle down with a bit of use.
Other than that, it may have a slight appetite for coolant (need to monitor
it), but then my 3.9 does that too, and so does the TD5 - I suspect a minor
leak in each case, not enough to show as actual drips, which is just
evaporating. Apparently, it had a gearbox replaced at about 75K miles, with
a genuine dealer replacement no less. which is nice.
--
Austin Shackles. www.ddol-las.net my opinions are just that
Travel The Galaxy! Meet Fascinating Life Forms...
------------------------------------------------\
>> http://www.schlockmercenary.com/ << \ ...and Kill them.
a webcartoon by Howard Tayler; I like it, maybe you will too!
Nige
"Austin Shackles" <austinDITCHTHIS...@ddol-las.net> wrote
in message news:t5gch5t3df277vdgs...@4ax.com...
Take the plugs out first, check for super steam cleaned ones. Odd it's
using coolant, the 3.9's did have liner problems i believe...
Neil
> Other than that, it may have a slight appetite for coolant (need to monitor
> it), but then my 3.9 does that too, and so does the TD5 - I suspect a minor
> leak in each case, not enough to show as actual drips, which is just
> evaporating. Apparently, it had a gearbox replaced at about 75K miles, with
> a genuine dealer replacement no less. which is nice.
Check the leads......make sure they are ok and that they are not crossed
incorrectly.
--
Neil
Dave Baxter
nospamplease.com says...
Check also, all the magement leads and connectors to all the engine and
related sensors. Airflow unit and lambda sensors especialy. People I
know in the industry who service exchanged ECU's say that 99% do not
have any "fault" themselves, but the internal logs are filled with
details of sensor errors. Most will keep the engine running (when
warm) with a "best guess" if a sensor seems to be playing up, but in
turn the driver often notices odd problems such as you describe.
In turn, they say, that most problems are of the "Lucas Prince of
Darkness" type, butchered or incorrectly re-assembled connectors,
letting the weather in, and electrons out as a result. Most often
caused by "gorilla tactics" of mechanics doing other jobs.
Of course, if coolant is getting out/in where it shouldnt, oooer..
I once had of all things (my first company car, passed down so I was not
it's first victim) an early 2l Cavalier i with the same symptoms you
describe. No coolant or oil leaks. But it kept burning out the airflow
sensor, & they kept replacing it (each month under warranty!) No one
wanted to accept that there was another problem somewhere.
My immediate past co-car, was perfect until it's first major service.
After that, each time you changed gear, the stereo "Crunched" through
all the speakers (worse at night with the lights on!) The main dealer
service types refused to accept anything was wrong, I found (eventualy
when I got p'd off enough to look myself) a loose bolt on a ground
strap. Strap re-secured (very dificult to get at, I can see why it got
left!) and problem cured. (And a "spikey" letter written to the service
manager!) Never did figure out why that bolt was loosened either, it
wasnt needed for the service.
Look for silly things like that, before digging too deep. It can be a
long and involved job though. Keep records of what you find (if
anything) and alter, so you can try and figgure out what affects it,
better or worse.
Regards.
DJB.
Lee_D
news:MPG.2581999e2...@news.btopenworld.com...
Austin,
Sounds like a bucket case. Stick it back on ebay.
Lee
Andrew Cleland
>
> "new toy" is a bit iffy about cold starting: fires easy enough but drops
> back to below idle speed and stalls when stone cold.
>
Mine did this after a rebuild - traced it to plug wires too close to the
main alternator - battery wire, so it was probably spikes in the 12V
feed to the ECU.
AC.
Austin Shackles
<austinDITCHTHIS...@ddol-las.net> enlightened us thusly:
Nicked the leads off the other one, and that made it better.
changed the plugs yesterday, no signs of steam-cleaning (phew!).
leads made a noticeable difference; so might lash out on some decent new
ones, will see how it goes. Might be worth getting the codes read, if I can
find someone with a reader - could give insight.
plugs ahow rich if fired up for a minute or so and stopped - but the other
day, when it'd been running for a while, they were more normal (though
perhaps still a tad dark)
airflow connection looks OK. Lambdas would be a good check point. I might
take it to the garage and get it on the EGA, see if that shows anything.
don't need poisoned cats...
Nige
> On or around Wed, 02 Dec 2009 10:35:54 +0000, Austin Shackles
> <austinDITCHTHIS...@ddol-las.net> enlightened us thusly:
>
> Nicked the leads off the other one, and that made it better.
>
> changed the plugs yesterday, no signs of steam-cleaning (phew!).
>
> leads made a noticeable difference; so might lash out on some decent new
> ones, will see how it goes. Might be worth getting the codes read, if I
> can
> find someone with a reader - could give insight.
>
> plugs ahow rich if fired up for a minute or so and stopped - but the other
> day, when it'd been running for a while, they were more normal (though
> perhaps still a tad dark)
>
> airflow connection looks OK. Lambdas would be a good check point. I
> might
> take it to the garage and get it on the EGA, see if that shows anything.
> don't need poisoned cats...
There was a sensor that caused summat like this, fucked if i can remember
which one it was.
Water temp rings a bell.
--
Nige,
BMW K1200S
Honda Transalp XL600V
Range Rover Vogue
Nige
> On or around Wed, 02 Dec 2009 10:35:54 +0000, Austin Shackles
> <austinDITCHTHIS...@ddol-las.net> enlightened us thusly:
>
> Nicked the leads off the other one, and that made it better.
>
> changed the plugs yesterday, no signs of steam-cleaning (phew!).
>
> leads made a noticeable difference; so might lash out on some decent new
> ones, will see how it goes. Might be worth getting the codes read, if I
> can
> find someone with a reader - could give insight.
>
> plugs ahow rich if fired up for a minute or so and stopped - but the other
> day, when it'd been running for a while, they were more normal (though
> perhaps still a tad dark)
>
> airflow connection looks OK. Lambdas would be a good check point. I
> might
> take it to the garage and get it on the EGA, see if that shows anything.
> don't need poisoned cats...
coils breaking down?
Andy
message news:t5gch5t3df277vdgs...@4ax.com...
>
>
> back to below idle speed and stalls when stone cold.
>
> once it's run for a bit to get warm (not up to running temp) it idles OK,
> although return-to-idle still drops below idle revs for a few seconds and
> then comes back up.
>
Same issue with my '96 3.9 V8i, fires from cold but if I engage reverse and
then go to Neutral the revs drop right off and it stalls. Once stalled it
will not re-start for a good 5 mins, just turns over and won't fire. Almost
as though it is flooded with petrol (If I am quick and get it into Drive
before the revs drop, and press on the gas it is ok and again once warm runs
absolutely fine.)
Could someone explain whey the leads being too close to things etc would
cause these symptoms but only when it is first started from cold?
--
Andy
Andrew Marshall
<austinDITCHTHIS...@ddol-las.net> writes
>leads made a noticeable difference; so might lash out on some decent new
>ones, will see how it goes.
Worth checking their end-to-end resistance with a multimeter if you've
got one to hand - showed up some 'gone-high' ones on my Minor 1000 back
in the summer. Ran a lot better with new ones.
--
Regards,
Andrew Marshall, G8BUR, M0MAA.
Unsolicited advertising matter unwelcome. Offenders may be blacklisted.
Austin Shackles
<andrew...@btinternet.com> enlightened us thusly:
I'm still thinking sensors. Can the ECU be read for fault codes in-situ on
these?
V8s are known for problems with shorting and cross-firing (firing the wrong
plug) if the leads are dodgy - which will be more likely if they're damp -
once the engine's running it gets warm and dries the leads out.
I still reckon the problem is a fuelling one though. This one is not quite
as smooth as it should be on the road (although a lot better with the decent
leads) - could still be leads, at that, although the set that's on it has
never shown issues on the other motor. At certain revs/throttle it's a tad
vibey, and I'm not sure it really pulls right in full-welly mode. Might
risk a compression test...
My cruise control is now similar to yours, fixed the vacuum pipes and not
working :-) I don't know if you get vaccuum unless the vehicle's in motion.
Cruise doesn't work under a certain speed, I've an idea about 28 mph BICBW.
Not that bothered, although like yours, it'd be nice to have it working just
because.
Andy
> My cruise control is now similar to yours, fixed the vacuum pipes and not
> working :-) I don't know if you get vaccuum unless the vehicle's in
> motion.
> Cruise doesn't work under a certain speed, I've an idea about 28 mph
> BICBW.
> Not that bothered, although like yours, it'd be nice to have it working
> just
> because.
>
> --
> Austin Shackles.
The pump is electric and should create vacuum once the master switch is
engaged, I have metered the 3 pins and none go to 12v so I think mine is
something to do with the inhibitor switch on the brake pedal or transmission
select. (It lets me remove the key with engine off and in any gear on the
selector whereas my 300 tdi only allows the ignition key to release if the
box is in park so I suspect there is some link here).
If it turns out that the pump is shot then it's staying shot as they are now
�300+ from LR!!
--
Andy
Lee_D
news:YqednSlYKtQ-6IbW...@bt.com...
> If it turns out that the pump is shot then it's staying shot as they are
> now �300+ from LR!!
Breaker?
Lee
Nige
"Lee_D" <newsgrou...@NOSPAMlrproject.com> wrote in message
news:4b1b8a15$0$2531$da0f...@news.zen.co.uk...
for a copy?
Lee_D
news:7o29q5F...@mid.individual.net...
Who let you off the play station! ;0)
Lee D
Dave Baxter
@btinternet.com says...
>
> "Austin Shackles" <austinDITCHTHIS...@ddol-las.net> wrote in
> message news:t5gch5t3df277vdgs...@4ax.com...
> Could someone explain whey the leads being too close to things etc would
> cause these symptoms but only when it is first started from cold?
When cold, the rich mixture needs a higher voltage to break down and
make a spark. That in turn creates extra high energy interference that
could just tip something over the edge into misbehaving. Other systems
(the alternator for one) will be working hard too, trying to recharge
the battery, and run everything else. That can (it can be measured) if
the engine ground strap is not 100%, cause other things to be
susceptable to the ignition interference.
Very lean mixtures too can create a need for higher voltatge spark, but
by then, everything else has warmed up, so all the operating levels and
timing could be different making a big difference in what it can mess
with.
In general, keep HV ignition leads well away from any other
lead/cable/wire if posible.
I once (many years ago) had an old V4 Transit (remember them?) where the
alternator would often die for no reason. Eventualy, someone told me
to move one of the plug wires away from it. It never needed another
alternator replacing after that simple "fix".
Modern cars are a collection of network'd computers, powered by an
engine. That engine in turn relies on all the compuers to be able to
communicate reliably with each other.
Bring back moggie minors, bobweight timing advance mechanisms and SU
carbs! Of course, a different era, and different faults and trouble.
The difference is, they are a lot easier to understand for most of us!
Cheers All.
Dave B.
Austin Shackles
<andrew...@btinternet.com> enlightened us thusly:
>
>> My cruise control is now similar to yours, fixed the vacuum pipes and not
>> working :-) I don't know if you get vaccuum unless the vehicle's in
>> motion.
>> Cruise doesn't work under a certain speed, I've an idea about 28 mph
>> BICBW.
>> Not that bothered, although like yours, it'd be nice to have it working
>> just
>> because.
>>
>> --
>> Austin Shackles.
>
>
>The pump is electric and should create vacuum once the master switch is
>engaged, I have metered the 3 pins and none go to 12v so I think mine is
>something to do with the inhibitor switch on the brake pedal or transmission
>select. (It lets me remove the key with engine off and in any gear on the
>selector whereas my 300 tdi only allows the ignition key to release if the
>box is in park so I suspect there is some link here).
On ours, the brake inhibit is a vacuum switch - there's a pipe to it;
pushing the pedal lets air in and stops the vacuum being there. dunno if
there's an electical switch too, mind.
>
>If it turns out that the pump is shot then it's staying shot as they are now
>�300+ from LR!!
--
Austin Shackles
<austinDITCHTHIS...@ddol-las.net> enlightened us thusly:
More:
the other day it was a complete twat to start fron cold. Eventually got it
to condescend to run, badly, and from reading the book that'll have killed
the cats, although that remains to be seen.
once it warmed up a bit, it was fine, all 8 pots chimed in and ran perfectly
OK the rest of the day.
next time it was required to start, it was slightly iffy and lumpy initially
but soon came to play OK.
Plugs been changed, leads off the other motor never gave any trouble there
and more to the point the other one runs OK on the leads off this one.
Checked the timing and it looks to be right and who was the arsewipe who
redesgined the front of the engine to put the serpentine belt on, fucking
nigh impossible to see the timing marks!
Next up: change the fuel filter in case it's starving slightly: this would
be most obvious when stone cold and running fully enriched. That would make
it balky to start and prone to miss, yet once it warmed up a bit and
demanded less fuel, it'd work OK. Other possibilities are the pump and
pressure regulator, leading to low fuel line pressure, although I'd have
thought that would be more persistent as a fault.
coolant temperature sensor is also a possibility.
JacobH
> On or around Wed, 02 Dec 2009 10:35:54 +0000, Austin Shackles
> <austinDITCHTHIS...@ddol-las.net> enlightened us thusly:
>
> More:
>
> the other day it was a complete twat to start fron cold. Eventually
> got it to condescend to run, badly, and from reading the book that'll
> have killed the cats, although that remains to be seen.
>
> once it warmed up a bit, it was fine, all 8 pots chimed in and ran
> perfectly OK the rest of the day.
>
> next time it was required to start, it was slightly iffy and lumpy
> initially but soon came to play OK.
>
>
> Plugs been changed, leads off the other motor never gave any trouble
> there and more to the point the other one runs OK on the leads off
> this one. Checked the timing and it looks to be right and who was the
> arsewipe who redesgined the front of the engine to put the serpentine
> belt on, fucking nigh impossible to see the timing marks!
>
> Next up: change the fuel filter in case it's starving slightly: this
> would be most obvious when stone cold and running fully enriched.
> That would make it balky to start and prone to miss, yet once it
> warmed up a bit and demanded less fuel, it'd work OK. Other
> possibilities are the pump and pressure regulator, leading to low
> fuel line pressure, although I'd have thought that would be more
> persistent as a fault.
>
> coolant temperature sensor is also a possibility.
Don't forget the 9th injector, that'd account for lack of richness on
starting if it's not operational!
--
JacobH
Bah Bumhug
Wisdom and experience come with age, they say, but I do wish I could
remember the darn question
Badger
"JacobH" <Geoff_Ha...@IEE.ORGasm> wrote in message
news:9uadnUYweYat8rjW...@brightview.co.uk...
>
> Don't forget the 9th injector, that'd account for lack of richness on
> starting if it's not operational!
>
Jacob, the 3.9 engine's 14CUX injection system doesn't have a 9th injector,
only the earlier 3.5 type with the 4CU "flapper" injection system.
Austin, I had similar issues on a customers 3.9 disco - tried replacing
everything, including fuel pressure regulator and every sensor on the damn
thing, right down to the ECU (and that's a right Royal pig to get at!) but
all to no avail. I eventually sussed it's starting issues....... read on.
Something for you to try before you spend too much more time on it....
Next time you switch off for the night, open the bonnet and kill the engine
by pulling the fuel pump relay (or fuse), NOT by switching it off at the
ignition. Once it's stopped, turn off the ignition and refit the relay or
fuse. Next morning, just turn the key straight to crank and see if it fires
up any better/smoother. DO NOT turn the ignition on and wait for the pump to
run or you will defeat the whole purpose of this test!
Did it start easier / better / smoother? If it did, then your injectors need
replacing because they are leaking and allowing fuel to pass after you've
turned the engine off, possibly to the extent that the pump priming prior to
starting is enough even to give an exceedingly rich mixture.
Did it make no difference at all? Well, at least you haven't spent any money
and you've eliminated any serious issue with the injectors.
Badger.
Austin Shackles
<brian...@btinternet.com> enlightened us thusly:
>
>"JacobH" <Geoff_Ha...@IEE.ORGasm> wrote in message
>news:9uadnUYweYat8rjW...@brightview.co.uk...
>>
>> Don't forget the 9th injector, that'd account for lack of richness on
>> starting if it's not operational!
>>
>
>Jacob, the 3.9 engine's 14CUX injection system doesn't have a 9th injector,
>only the earlier 3.5 type with the 4CU "flapper" injection system.
>
>Austin, I had similar issues on a customers 3.9 disco - tried replacing
>everything, including fuel pressure regulator and every sensor on the damn
>thing, right down to the ECU (and that's a right Royal pig to get at!) but
>all to no avail. I eventually sussed it's starting issues....... read on.
>
>Something for you to try before you spend too much more time on it....
>Next time you switch off for the night, open the bonnet and kill the engine
>by pulling the fuel pump relay (or fuse), NOT by switching it off at the
>ignition. Once it's stopped, turn off the ignition and refit the relay or
>fuse. Next morning, just turn the key straight to crank and see if it fires
>up any better/smoother. DO NOT turn the ignition on and wait for the pump to
>run or you will defeat the whole purpose of this test!
I'll try that, might need some nifty work with the immobiliser that's on it.
Although I could lock it and unlock it, that leaves the immobiliser off for
about 30sec.
>Did it start easier / better / smoother? If it did, then your injectors need
>replacing because they are leaking and allowing fuel to pass after you've
>turned the engine off, possibly to the extent that the pump priming prior to
>starting is enough even to give an exceedingly rich mixture.
>
>Did it make no difference at all? Well, at least you haven't spent any money
>and you've eliminated any serious issue with the injectors.
Started it today, first few times it fires and dies, then it fires and won't
reliably idle or pick up off idle, then after a bit it will pick up and run
OK.
It feels like lack of fuel, I could believe something like the pump being
idle or the pressure regulation being iffy or something, making it slow to
build rail pressure - so the first could of attmepts there's not enough
fuel.
I'll be changing the fuel filter (since it's likely it hasn't been chanegd
for a while) in a bit. I'd have though that a slow pump would be more
problem all the time - last time I had one of those, it'd only run at idle -
but the symptoms were a bit similar to this - dies as soon as you tried to
increase the revs. However, on that one, the symptoms were persistent and
didn't go away.
JacobH
Thanks Badger,
I didn't realise the 3.9 only came with the hotwire, I was more worried
it was a carb motor and I was totally out in left field rather than only
being 'out' in the infield!
Austin Shackles
<Geoff_Ha...@IEE.ORGasm> enlightened us thusly:
heh. Rangies had flapper on the 3.5s and hotwire on the 3.9s as a general
rule. 3.5 injection discos are hotwire as well.
This is a later 3.9 disco with the seprentine belt. interestingly, the
disco I manual (on RAVE) lists still another set of fuelling - which, I
guess, may be the 4.6, if they fitted the 4.6 to disco I.