Have I been sold a duffer 2 LPG Vectra, HELP!

Sorry have to repost this as a new topic as I want to cross post this
to other groups.

3 weeks ago i bought a Vauxhall Vectra 02 Model (last of old shape) LPG
factory fitted. Engine Z18 XE.

My 3 problems:

1] When driving at a constant speed or accelarating on both motorway
and town on LPG or Petrol I suddenly at random interval (say every 5-10
minutes) lose all engine power so pushing the accelartor pedal to the
floor gives no power. But If I then take my foot off the accelarator
and put it back on then the power comes back instantly. Bit worrying at
80 Mph in the fast lane. I get no revs whatsoever until i re-engage.

2] Wasting lots of fuel both LPG and petrol. I am getting about 3 miles
to the litre in town traffic and about 5 miles per litre on the
motorway. I have measured this by driving 200 miles on a full tank then
filling up straight away back to full.


3] Engine electric light remains on, until reset. "Engine block in an
amber light" on the dashboard. The car manual advises that it is a an
engine / electrical problem.

Had the following error codes come up on a Snap-On Graphing Scanner.

P0170 Mixture Rich
PO134 Undocumented code
P0571 o2 Undocumented code

There was also an old error code reported that was repaired by the
previous owner:
P0335 Crankshaft Position incorrect. This code looks like it was not
reset.


Mechanic believes it is Thermostat as the engine temp never goes above
76 degrees, the thermostat is cutting in too soon. so even after half
an hour of letting the engine rev the temp didnt go up.

The Scanner was reporting that the o2 mixture before Cat on bank 1 was
rich. The mechanic also stated that a particular o2 meter should switch
between 200 and 800. However mine always stayed between 300 and 600.



Mechanic decided to change the thermostat/housing unit with sensors:

Engine light hasnt come on (after 10 hours).

Engine temp goes upto 90 degrees befor the thermo kicks in then rise to
100 Degrees and fan kicks in. The before cat mixture now switches
(flip-flops) between rich and lean.


Problem 1 NOT FIXED!!: On acclerating in LPG or Petrol i still lose
all power until acclarator pedal is re-pressed from the top, ie let go
off the pedal completley and repress the pedal.

Problem2 also Im not too happy with still seem to use a lot of petrol
or LPG will report back with more accurate figures as i go on.

Problem 3 Light has gone off.


Any ideas on further fixing Problem 1 and 2. is it a GAS issue? even
though it affects both fuels.

 

Code P0134 O2 Circuit No Activity Detected (Bank 1, Sensor 1)
Code P0571 Brake Switch A Circuit

Considering that most of the codes related to a bad O2 sensor, I am
surprised it was not changed.
A bad O2 sensor can caused stalling, even at high speeds.

 

Usually best to sort out the problems on petrol first. Unlikely that a
gas issue will affect running on petrol.

 

You might want to check the wires to it first though.

 

I dont have any direct experience with factory fitted gas, but I've been
running converted cars for some time now. The first thing I would
look for is if you have a leaking blowback suppressor. This is a device that
lets out an explosion in your inlet before (hopefully) it destroys anything.

Inline ones look like a metal ringpiece up to 1" wide with a rubber band
around it. they have a flap inside that moves aside under induction,but
slams shut under blowback and vents the gas past the rubber band. if you
have one then check that the band is forming a nice tight seal. might be
that its a bit sloppy, and taking your foot off the pedal provides enough
suction to seal it again.

other kind look like a hinged circle on somewhere flat like an air filter
box. overpressure lifts the flap and vents, usually a spring pulls it shut.
again, check for leaks.

I find the thermostat bit interesting. if its faulty and running cool then
the ecu will treat the engine as just started and will adjust the mixture as
if just started, i.e. rich.
you say it goes up to 90 then fan comes on. is this stationary, or will it
do this when driving sensibly (not thrashing it) on level ground?

another thing would be to have an emission test done. on lpg the petrol
injectors should shut down. but the fuel pump usually doesnt so they are
still pressurised. if worn they will leak. this plaged my old range rover.
result was increased consumption and very rich running. if the HC is high
when on gas then you might have bad injectors, but sometimes just running an
injector cleaner in the tank can help. didnt with me. my solution was to fit
a switch to manually shut down the fuel pump
myself. also a handy immobiliser....

Hope this gives you something to go at.

Mike

 

Rubbish!

The o2 sensor can only influence fuel trim by around 15%, and using full
throttle will cause the ECU to switch to a fixed fuelling map, and either a)
totally disregard the o2 sensor, or b) more likely on very recent engines;
use a fixed map which it has trimmed from previous experience.

It would appear the OP still has a long term fuel mix rich mix on gas, but
not excessively so, according to his o2 sensor voltages.

There is an underlying problem which is causing the cut outs, probably a
sensor or wirng problem.

Alas he doesnt seem to be able to find a well experienced enough technician
who is familiar with the LPG conversion to sort the root cause, although
fixing the thermostat and o2 sensor was a good start.

The LPG ecu may well need reprogramming, as the tuning doesnt seem quite
right either.

Tim..

 

I am fairly sure the main problem is a faulty brake light switch. If you
rest your foot on the brake pedal and try to drive after about 20 secs the
ecu returns engine rpm to idle - it can't see why you are braking and
driving at the same time.
The switch has 2 circuits in it -1 for brake lights and 1 for ecu - I bet
you £1 the second circuit is staying active all the time.
If you take the trim off above the pedals and get hold of the pin in the
switch and pull it out against it's ratchet (with pedal down) and then let
go it will reset itself and you will probably find you have cured the fault
at no cost - apart from the £1 you owe me!!!!
I work a lot on Vauxhall LPG and apart from dirt problems they are very
reliable.

 

Tim, I have over 30-years experience in the diagnostic business, and will
restate the claim that a bad O2 sensor can, and frequently does , cause high
speed engine stall.
A classic case would be the Rover group. An after-market universal O2 sensor
fitted to a Rover, have been known to cause the ECU to fail completely, and
only dedicated O2 sensors can be used.
Whilst the vehicle is a Vauxhall, a short in the sensor can intermittently
spike the ECU.

 

The fuel consumption is dismal and error readings show rich mixture. This is
affecting Gas and Petrol.

Just a thought could there be an air problem?

Is the air filter clear? Is there some other restriction to air flow.

good luck

H Matthews

 

There is a good possibilty that you are correct. Brake sensor feedback is a
relatively new idea on Vauxall cars, and from the mapping it seems that this
switch can cause the ECU to switch off the injector circuit, much the same
way that a closed TPS on a decelerating engine will cause the injectors to
close.
That is the problem with newsgroups. We don't get hands-on to the engine in
question. A decent analyst would get streaming data during a test drive, and
the fault would be obvious.

 

Thanks always impressed by the helpfulness and the knowledge on usenet.

Took it in today after getting the ECU light on again, the following
faulty codes were read:

P0134 o2 Circuit No activity detected (bank 1 Sensor 1)
P0170 Fuel trim bank 1 malfunction
Both same as last time:

So Mechanic did what most of you suggested:

1] changed Lambda and this seems to have corrected the fuel mixture
problem!

2] executed me140's Brake light fix.
Me140 I owe you a quid!!!! It seems to fix the power loss problem

However I am still not that happy about the fuel consumption Im only
getting 5 miles/litre on the Motorway????????

This was measured by filling the car to top, then driving 50 miles and
refueling back to top.

I will re-investigate and re-measure but still not satisfied with my
result.

Further investigations were also carried out by mechanic:
The car drives nice the spark plugs were examined they very clean. the
power compression was measured on each

spark and was spot on 1200 (??). Another flow (maybe fuel) was measured
that was spot on at 3.8... But couldnt figure out this bad fuel
usage??


thanks to all again were getting there, one thermostat down, One Lambda
down,and a brake switch reset.

So any other suggestions??

 

If his diagnostic machine reads data as well as fault codes it would be nice
to know what the short term and long term fuel trim readings are.
I wonder when last time LPG pressures were checked too?

 

If he's using 1 litre of gas per 5 miles, its got to be running pretty rich
which surely the o2 sensor would pick up on. Plugs dont blacken on a rich
lpg mixture as they do on petrol.

Has the lpg gas pressure been checked, and can you confirm what the mpg is
like on petrol?

Tim..

 

However I am still not that happy about the fuel consumption Im only

Well you don't say how you drive!

If I do 80ish, I can get my Volvo 850 to return 21mpg which isn't that
different to your 23mpg. On the other hand if I drive a nice 60, then I
can return nearly 29mpg.

What I will say is that 50 miles isn't enough to get a good indication
anyway as filling pressures etc may vary. Go empty to empty.

David.

 

For reference:

my 04 Vectra LPG has returned 5.49 m/litre over a two month period. I have
been unable to get a sensible measure on fill to fill because full is never
the same twice.
However don't be downhearted. 5.49m/l at 36p /litre is equivalent to 14m/l
(63mpg) at 92/l for petrol.

Matthews

 

Is that gas or petrol? If petrol and its not a T5 then its very heavy. At a
steady 80, ours does 34-35mpg.

Tim..

 

Is that gas or petrol? If petrol and its not a T5 then its very heavy. At a

The petrol thing on the dash used to report 28mph on petrol and then on
gas I usually get 26mpg.

You don't say what car you have specifically but I'm not sure the
comparison with the T5 would be equal anyway. I used to have a Saab
9000 2.0 light pressure turbo which would return about 28mpg. I have a
9000 Aero with 50% more power which on a run returns over 40mpg because
of very high gearing which it can pull due to having much more torque.
28mph per 1000 rpm in top.

David.