B

big-bad-bob-pad

New Member
MY 1995 4.0 SE has an intermittant misfire and loss of power.
Ive checked and cleaned what sensors/connections I can get at, as well as renewing the plugs and leads.
I finally gave in and got a mate to read the engine codes.
The only fault was 'Bank 1 Camshaft Sensor' but that cleared OK and didnt come back for the 30 minutes I had the car 'plugged in' and running.
With the car sat idling the engine data was:
Bank 1 long term fuel trim = -100
Bank 1 short term fuel trim = 8.6
Bank 2 long term fuel trim = -100
Bank 2 short term fuel trim = 8.6

When the car was revved (3000+ RPM) for about 10 seconds, the readings changed to:
Bank 1 long term fuel trim = -51
Bank 1 short term fuel trim = 6.3
Bank 2 long term fuel trim = -51
Bank 2 short term fuel trim = 20.4

My mate has no idea what these figures mean !
I suspect that I have a loose camshaft sensor and that bank 1 is running far too lean.
Can someone please explain what these figures mean and what my next course of action should be ???
Not sure if I need an adaptive reset or should find out why the bank is running lean in the first place.
The MAF and O2 sensors all seem to be signalling OK (rapidly changing).
The car is LPG converted and does a lot of miles on LPG (20k+ per year). Has this happened because I run it on LPG so much ????
 
try checking the wires to the cam sensor, also take it out and inspect it.

i really doubt its the lpg thats caused it. if the lambdas read ok then its not a fuel caused issue as these would chuck a wobbly.

the only way the lpg could cause it is if the lpg was set up wrong thus the enjine ecu would be trying to adjust the mixture on the lambda readings. check lambdas on lpg and petrol. do you have the software for the lpg kit?
 
Thanks for the reply.
No software for the LPG kit unforunately, but will try and find the cam sensor.
Do the fuel trim figures sound OK though ?
 
no they don't, mine was at 24 on bank 1 long, i got worried, checked the lpg side and found lambda had packed up. it was over fuelling!!

what lpg kit have you got?

find the ecu and take the details, i'll see if i can find the right soft/cable.
you will have to get both petrol and gas running as close to eachother as possible, that way you avoid the petrol ecu going way out.

it doesnt matter in theory if you run mainly on lpg as you will only start on petrol then flick over. i run on gas straight away except for the coldest of mornings!!! but it is best to have the petrol side running perfect as this is what you'll use if theres a problem with the lpg and your far away from home. it happened to me, the lpg ecu burnt out and i was 200 miles from home!!!
 
I'd check the Lambda sensors and/or the fuse the feeds them. On the Disco 2 the same fuse feeds both these sensors AND the camshaft sensor.

The fuel trims should be roughly in balance, both short-term which will juimp about a bit, and long-term which should be more stable.

Our Zavoli LPG manages to keep it all pretty stable once everything is up to temperature.

Petrol fuel trims might be out if you haven't run it far on petrol lately.

Peter
 
Ive checked the cam sensor (strange to find it under the water pump) and all looks healthy. I had the water pump changed about 4 months ago so this could explain the fault code.
The LPG ECU is an OMVL Dream XXI unit. The details are:
Tipo ICU
COD. AEB2568
B2158124

I tried the car on petrol only this morning and it struggled to tick over until engine warm. Popping through the air intake like a machine gun.
Going onto LPG cured all this, until after about 10 miles then power dropped off and all problems returned.
Could one bank be running lean because the lambda in the cat throws a wobbly when its hot ???
 
What LPG injectors is your car running? The original OMVL ones supplied with the Dream kits were cr-p.Even when new it was difficult to trim them properly.I have two regular customers running the Dream system,one now has Matrix injectors,(Very good.)the other has Keihin injectors,good - but noisy as its on a 3.9v8 in a RR Classic.(Bank fired,not sequential.)
It may just be that the ecu is fed up with poor trimming from the original injectors not following accurately what the petrol ecu expects its own injectors to do.
Dont worry too much about the actual short term trim values as long as they keep moving and dont get to a value of + or - 25.Individual engines run differently according to wear etc.
 
Ive tried the MAF sensor trick but the engine didnt run any different. Cleaned the MAF sensor and things improved slightly.
The LPG has run very sweet for years but suddenly dropped off. Getting slightly less MPG but trip computer still showing 14.8MPG.
Whilst I agree that the symptoms sometimes resemble a MAF fault, the lean running figures bother me.
For the first 15 miles of running with LPG, the car runs perfect, easilly breaking the speed limit :mil43: but then the power drops off until the slightest hill causes it to slow down whilst I can barely maintain 70MPH on the flat.
Switching to petrol gives me 'slightly' more power but the car only properly responds if I plant my foot to the floor (on petrol) which causes a huge backfire followed by huge accelleration. Trying this on LPG does nothing !
I'm fairly handy with the spanners but I'm struggling to find a 'simple' cure for this. Its beginning to look like I will have to teach myself computing to fix this !
 
Okay !
Hooked up everything and took my usual route to work.
Noticed that No.2 lambda sensor was OK at tickover but under load (anything above 10MPH) it went to 0.02v and stayed there. This sent the fuel trim to 24%.
In comparison, No,1 lambda reading was flickering around all the time and the fuel trim figure was also changing all the time (16% to 24%)
When I booted it, both lambda's went to 0.02v and fuel trims to 24%.
My OBD software says that bank1 is running rich and bank 2 is lean.
Not sure about this conclusion as suspect that bank 1 is OK and bank 2 is lean.
My guts tell me that No.2 lambda is knackered due to the flatline reading, can someone tell me if I'm right ???

P.S.- The crank sensor fault had re-appeared but cleared again and didnt appear for entire journey to work (40 miles). Checked in service history and sensor was changed 4 years ago. Are these sensors known to fail ?
 
big-bad-bob-pad said:
Okay !
Hooked up everything and took my usual route to work.
Noticed that No.2 lambda sensor was OK at tickover but under load (anything above 10MPH) it went to 0.02v and stayed there. This sent the fuel trim to 24%.
In comparison, No,1 lambda reading was flickering around all the time and the fuel trim figure was also changing all the time (16% to 24%)
When I booted it, both lambda's went to 0.02v and fuel trims to 24%.
My OBD software says that bank1 is running rich and bank 2 is lean.
Not sure about this conclusion as suspect that bank 1 is OK and bank 2 is lean.
My guts tell me that No.2 lambda is knackered due to the flatline reading, can someone tell me if I'm right ???

P.S.- The crank sensor fault had re-appeared but cleared again and didnt appear for entire journey to work (40 miles). Checked in service history and sensor was changed 4 years ago. Are these sensors known to fail ?
Click to expand...
Yes,they are known to fail and dont log codes for no reason.Your #2 oxy sensor may be tired,but its not knackered - for it to switch down to 0v it has to be working.I would suggest what has happened is the long term trims are so far out that it wont run on petrol and the lpg vaporiser,filter and injectors all need servicing.
Have you tried resetting the petrol ecu adaptions and then viewing the fuel trims ? And dont let it backfire anymore or you will kill the MAF.
 
Ive just been playing with the OBD stuff again and No.2 Lambda is sending the short term fuel to 24% at tick-over. No.1 (in comparison) is at 6%.
Suspect you are right about the LPG side of it but it was serviced in summer so should be okay.
How do you reset the petrol ecu adaptions or do you have to pay someone for an adaptive reset ?
 
Adaptive reset is usually just taking the battery off for 5 minutes then reconnecting, and driving the vehicle normally on petrol for 40 miles or so. That allows the engine ECU to start over with the fuel trims.

Before you do it, read up on how to save your door alarm/remote settings FIRST!

Peter
 
listerdiesel said:
Adaptive reset is usually just taking the battery off for 5 minutes then reconnecting, and driving the vehicle normally on petrol for 40 miles or so. That allows the engine ECU to start over with the fuel trims.

Before you do it, read up on how to save your door alarm/remote settings FIRST!

Peter
Click to expand...
Peter,that is not the case,it will not reset the long term trims.it needs doing on Testbook or similar,and the LPG needs trimming whilst watching the petrol trims then adjusting the LPG settings to match.
 
Many thanks for all the help.
Ive sourced a couple of new lambda sensors and will get the adaptive reset done when have swapped the sensors.
Plan to run it for a while on petrol before get LPG trimmed to match.
Will keep you posted how it goes !

Cheers chaps !
 
Sounds similar to what my D2 was doing, faultmate giving codes of misfires & fueling out of limits.

Traced to faulty coil packs, ok when cold played up when hot, quite common apparently.

LPG tends to show up any slight weaknesses on the HT side.

As for the LPG tune from what Ive been told the LPG ECU (Zavoli Alesi) on my car should do exactly as the Motronic ECU tells it.

Local specialists (Rpi Engineering & Jaymic Systems) were most helpful with advice on the LPG system & how it interacts with the Motronic.
Both advised that the Motronic system & to an extent the GEMS are very 'fussy' for the want of a better word as to where the LPG injectors are situated, must be as close to the inlet as possible in the lower manifold, not in the upper part as some I have seen are.....
 
You must log in or register to reply here.

Similar threads

MAF Diver
Disco 2 Rough idle in a V8 D2a — tried MAF, O2, sparks, leads
2
Replies
35
Views
3K
marjon
marjon
H
Finding source for vibration/lump at idle
Replies
2
Views
1K
HACKCHILD
H
H
Chasing down engine vibration/judder
Replies
6
Views
955
Nodge68
Nodge68
H
Chasing down engine vibration/judder
Replies
2
Views
619
HACKCHILD
H
F
Freelander 1 V6 won't start
Replies
2
Views
675
Nodge68
Nodge68