Mystery idle problem

Well this one has me stumped

I have a 4.6 P38a on gas with a recent new engine (so no comments about cracked blocks and slipped liners

The damn thing refuses to idle... sometimes!

it is completely random I cross my fingers every time I turn the key and sometimes it runs fine others it just will not idle and I have to drive "left foot braking" to keep the revs up with the other foot
For one this is killing my brakes and for another it is damned annoying.

After I have driven it for a little while if I stop and say go to a shop or fill up with gas more often than not when I return to the car it is fine

however if I stop and sit in the car and wait then try again it still refuses to idle
It knows I am sure !

Anyway anyone got any ideas where the fault might be some kind of sensor I suspect, but which one !

Regards
Nevyn

'96 'finched P38a with new engine on LPG

Unfortunately mine has just stared to do the same thing but only when run on LPG

Am haing it looked at now but the LAndrover specialist is foxed at the moment

Get everything to do with the oxygen sensors checked - not just fault codes,but all their cabling etc.If that is ok then you need to get the oxygen sensors hooked up to an oscilliscope to monitor their outputs - whilst driving.This should provide better info as to what is going wrong.

Bob Gontar
My 4.6, when it runs again, is lpg. I had the same problem only on gas. Depending on your system, an agent should be able to reprogram it.
Check the net for lpgpartners.co.uk and they should help.

Hi

Just to update you guys
it does it on Petrol too and runs worse on petrol than gas

if I run on just petrol for a few days it does it less often but still has the fault

I have been told I should check the throttle stepper motor and so will let you know how this works out...

any other suggestions welcome

Nevyn

you may have a ht ignition problem, perhaps a lead or plug problem. cheapest thing to check first
regards phil

Hi m8
Had a pretty much the same prob on mine not ticking over at first then mine reved to high when it was ticking over , had the car reset to facrory setting on the rover com. solved the prob for me hope this helps ,mine runs better on gas to.

tiny

ONLY A THOUGHT BUT I HAD A SIMULAR PROBLEM ON A JEEP GRAND CHEROKEE( WORST CAR IVE EVER OWNED, YANKY PIECE OF ****).
HOWEVER I CHANGED THE LAMBDA SENSOR IN THE EXHAUST AND ALL WAS SWELL , UNTILL THE ****ING THING BACK FIRED 2 MONTHS LATER AND BLUE THE AIR BOX INTO A MILLIAN PIECES.
ps
auto gassing a car is a bad idea.

Hi Guys

Just to let you know i had the same problem when i converted my 2001 4.0hse to gas there was a number of problems you need to address as follows:

1.correct ecu file for your gas ecu (mine was incorrect which blew 2 sets of cats)

2.changed my ignition leads to magnecor (rpi engineering as for chris crane top bloke)

3. plugs mine had the incorrect plugs in ngk mine can only use champion double platinum tipped try bearmach cardiff £62 for the 8

4.remove your cats and get 20 more horseys

5.YOU WILL PROBABLY FIND AFTER CHANGING ALL OF THAT ITS THE MASS AIRFLOW DEPENDING ON MODEL £85-£106

6.after replacing or before replacing mass sensor get it on rovacom i paid £45 the previous garage didnt reset the adaptive settings

7. good luck after all your gonna need it cause its a rangerover

Thanks for all the replies guys

Just an update for you
I took the stepper motor off and cleaned it up, it was reaqlly gunked up
anyway after this it seemed to run purrfect for about 3 weeks now it has started to do it again so well back to square one

I will try some of the suggestions here, it is a new engine so I think perhaps the rovercom reset is a good start because all the heavy stuff is new just the electronics original and with gasflowed heads it may be confusing the poor British computer

I'll keep you posted

Nevyn

Check both breather lines for blockage, do not forget to check short pipe from RH side valvecover after taken hose off. There is oil separator which can be blocked and causing problems.

I had severe idling problems last winter, found nothing wrong and Rovacom shows nice readings and no codes.
Checked breather hoses once again, and LH was good(from valvecover to throttlebody).
RH was quite badly restricted(from RH valvecover to plenumchamber), especially that short pipe on valvecover, actually i need to take whole cover off to get it cleaned.

Car idles better than ever after that.

Aaaaaargh

Right so i changed the stepper motor on the inlet and Woohoo it was fixed!

ran lovely for a couple of months well pleased

Now it has gone nuts on me again
It constantly idles at 2000 revs and has developed a bit of a misfire too

any suggestions
has my stepper gone again?

is there something else to look at ?

Nev

I Read Somwhere In This Site That The Risk Of This Problem Is Less In Petrol Motor Than In Gas ??
I Don't Now If That Is True Or False ..

I think I have solved the problem

I disconnected the battery to re-set the computers and it seems cured for the moment

I think think the gas ECU got it's knoickers in a twist and was sending a confusing signal to the main ECU

I will post again if the problem returns

Nevyn