Help! Still have running problems

[s111Truck_cab]

Well my 94 3.9ES auto disco has had new Lambda sensors and all exhaust leaks fixed today with no change to the poor running. It hesitates on take off, misses, has very low tickover and stalles. I have taken of the stepper motor and it doesnt' move atall unless pushed very hard against something or if pulled very hard. I was told at my indipendant land rover garage that the stepper is not used when warm-is this true. Also if unplugged no change to the engine running is made. The ignition system has been checked with no faults, a hydrocarbon test as been done on the coolant with no problems and a compression test has also been done with no problems. It uses no coolant, oil and doesnt smoke. It has had new genuine coil, rotor arm, dizzy cap, plugs and leads. I'm at a total loss. help!

[Jon v8]

Has anyone checked to see if the new oxygen sensors are doing anything ? Are they being heated ? Dont force the stepper in and out - you'll break it.And yes it is used to control idle speed during warm up,it doesnt sound like they know too much about how it works,is there any one else you can take it to ?

[s111Truck_cab]

I have ordered a new stepper motor. How easily should the plunger move as mine is rock solid and takes lots of force to get it to move?

[Jon v8]

Its a little electric motor with a thread on the plunger shaft - thats why it does not want to move.They often get blamed for poor running or idling issues - wrongly,unless they are clogged up with gunge.It wont cause a misfire either,this is more likely to be caused by the oxygen sensors failing to switch - either cos they are shot or because they arent being heated.They are supplied with battery voltage via the fuel pump relay from the centre terminal.If they arent heated they will only be hot enough to switch under heavy load.This means the Ecu will push the fuel pulse width all the way to one end of the fuel map and cause poor idling.

[s111Truck_cab]

Hi, so where is the fuel pump relay? I may try and swap it at my independant land rover garage with a known good one to see what happens. It is crap at tickover on petrol and gas plus it stalls. It doesnt feel too bad on petrol when it is being driven just bad at tickover. Gas has a missfire during driving and stalls at tickover.

[s111Truck_cab]

So guess what, the new stepper motor made no difference. Will sell the old one to try to get back some of the £70 the new one cost. Off to get a new fuel pump relay tommow.

[s111Truck_cab]

Well I went to my Land Rover independant today to get a relay and they had a quick look and said it was okay. So it is booked in for next friday for them to go through the wiring, as they think that the lambda sensors arnt comuncating with the ecu propperly-possibly where the lambda sensors are wired into the lpg system. Which is making it run lean causing lean missfire.

[NomadABC]

Jon, I think you might be talking to yourself here ;)

[charley_bucket]

Huh, no we're still listening,
after reading this much into the mysterious
ways oh the many ways they can foul up,
I for one will keep an eye peeled to see how this turns out!
G'day~

[s111Truck_cab]

Hello, my Disco has just come back from my independant Land Rover garage. They have tested every wire and swapped every sensor, ecu, and found no faults anywhere. The lambda sensors just keep giving a negative reading which they are now convinced is to do with the lpg ECU being faulty or not set correctly. I now have to order a cd and connection lead so as to connect it up to a comp to see what is going on. They have all the software but the one for mine which is a BIGAS Sequential system. Anyone know about lpg systems?

[tonywitney]

Its a BIGASS system? :D Sounds about right, but I really hope you get this fixed, and it seems like you're on the home stretch now.

[Jon v8]

Hello, my Disco has just come back from my independant Land Rover garage. They have tested every wire and swapped every sensor, ecu, and found no faults anywhere. The lambda sensors just keep giving a negative reading which they are now convinced is to do with the lpg ECU being faulty or not set correctly. I now have to order a cd and connection lead so as to connect it up to a comp to see what is going on. They have all the software but the one for mine which is a BIGAS Sequential system. Anyone know about lpg systems?So does it function properly on petrol ? This is where you start,there is no point AT ALL in fiddling around with the LPG till it is perfect on petrol - everyone who dabbles in LPG knows this.

[V8_Disco]

Jon as always is Bang on with his advice! Get it to run Perfect on Petrol ...

Aidan

[s111Truck_cab]

Have spoken to my landy specialist and he said that they changed the petrol ecu and it is almost spot on now on petrol but still hesitates on lpg. I have only driven it today as it was delivered yesterday and it is much improved on petrol and much better on lpg but has a slight stumble or hesitation only on lpg now with a slight miss on both. So they think that the lpg ecu isnt set up right and is not allowing the lambda sensors to switch. The lpg ecu is linked into the petrol ecu and piggy backs of it. They say that when the software for the lpg system comes all will be sorted in a few mins wired upto the laptop. They have had this problem before but with different lpg setups.

[Jon v8]

You still have not got it,if there is even a slight miss or hesitation on petrol then its not right.You should be able to snap the throttle open and the engine just picks up and revs,if it doesnt then there is something wrong.Most Lpg systems piggyback off the engine ecu,either from their oxy sensor feedback or injector pulse width.Some just feed a signal into the petrol ecu to keep it happy whilst using info from its own,(usually single) oxy sensor.Its not a big deal to have the software and connector to modify how the LPG ecu runs.
Till its 100% on petrol,it wont be right.

[s111Truck_cab]

Well it has been a while now since my last post on this problem. I have just lived with it missing and stalling for a while now. A few days ago I had the LPG system gone through with no problems found. The missing on petrol has been getting much worse and it feels very lumpy at tickover. On gas it misses throught the rev range and hunts then stalls everytime i come to a stop. I knew when it had new head gaskets at my local garage that my landy specialist said that when they do the heads they get them skimmed and have new valves plus hydraulic tappets fitted and that my local garage did a bad job. They do know there stuf as i often take it to them to rectify problems that my local garage have caused and cant fix. I just take it there to save some money. It cost me £450 to have the gaskets done and my specialist landy garage said it would be £800 for new gaskets, heads skimmed, new valves and new hydraulic tappets. So I think I will have to take the plunge and get the top end done properly as I'm very sure it is a sticking valve or tappet. Everything else has been replaced or checked with no change-plus it uses no coolant.

[alfapat@dsl.pip]

I am watching this thread with interest as I guess JON is right, if its not right with petrol it will never be right.
I have a simiar problem which is posted here and I was directed to the rpm sensor, if the wires are not clean at the ign coil as I believe that is where the signal is taken from then it wll never work , but I have come to sticky end and the old beast will not even start now!

[freelanderPX54]

If testbook doesn't come up with your problem then why don't you find someone with a rolling road set up to try. They will be able to find where in the REV range it is causing problems