erratic idle

[matbor]

Well I need help, I have been having the same problem with my 97 v8 disco (Auto) for nearly 2 years, for some reason I always get erratic idling, usually happens when I go from drive to reverse or vice versa the idle drops a little and then bounces back up (sometimes nearly stalling) or when I'm sitting at the traffic lights. I have had it to a number of LRO mechanics in Melbourne, all trying different things, but the thing never really does it when it is at the mechanics (I think that they think I'm crazy !!!), the other thing I notice is that when I get them to tune the car it will last about 2-4 weeks before it starts doing it again. Also this car is maintained religiously, with oil and filter changes every 5,000kms, and goes to the LRO mechanic for a tune and check up every 10,000kms. car has done 130,000kms now.

These are the parts I have had replaced over the last two years, trying to cure the problem :
* air flow meter (x2 both secondhand ones)
* stepper motor (x1 new one)
* new plugs (every 10,000km's)
* magencor leads (less than 30,000kms ago)
* new distributor rotor (less than 20,000kms ago)
* new distributor cap (less than 20,000kms ago)
* all injectors cleaned professional (less than 30,000kms ago)
* clean the breather T-piece all the time
* always check the clamps around the hoses on the AFM.

Any ideas, on what you would check next, I really want to solve this problem and am sick of LRO mechanics at the moment, so if anyone has a list of ideas on what I could try in order that would be fantastic.

Thanks
Matt

[LandyAndy]

Hi Matbor
I had a similar problem with a XE EFI falcon.I took it to a mechanic mate,he used CRC and sprayed it on all intake joints(using the pipe supplied with can) starting at the airflow meter and working to the motor.The reason is to find an "un-calibrated"air intake that the computer is having trouble dealing with and so adjusts the idle up and down as the air leak changes with engine revs.A leaky gasket will make the engine rev as it gets extra "fuel" from the CRC, thus revealing the air leak.
This is worth trying but is hard to see how it ties in with the problem going after a service.
Goodluck
Andrew

[harry]

8) g'day matbor,
my 95 disco does this pretty regularly, and its irritating.
on mine it is the stepper motor that causes the problem
mainly hunting at idle at the lights - especially after stopping at the first set of lights following a highway run at around 100-115 kph fortwenty minutes or so.
so i know what distress it causes.
i pull the stepper motor out when i get this happening and squirt it with carby cleaner, shake it out and give it another squirt, also squirt in where the stepper motor goes.
the stepper motor has a big nut and large diameter thread, but it appears to be made of diecast crap so don't get too heavy handed doing it up, or you will strip it.
mine i do up by hand then just nip it [i think mr land rover loctites the thread] then when it plays up i can whip it out by hand.
of course your problem might be something else,
good luck and lets hear how you go with it.
8) harry

[matbor]

nope cleaning didn't work, i think it is getting worst, it is very hard to reverse now, looks like i'll have to go to LRO tomorrow otherwise i want be able to drive it !!! Any other ideas before that. also cleaned the t-piece again.

matt.

Update 7pm:
on the way home tonight it seemed fine, only time it really played up was when i was backing into my car park at home it would idle funny

[shaunp]

All the cleaning of stepper motors in the world won't fix it if the base idle is set low, you need to make sure this is correct. The stepper needs to be cleaned and lubed every service in my opinion and the base idle set. Next Auto cars have a switch on the shifter that lifts idle when in gear, I haven't seen one fail but maybe you have a dirty one. Manual cars have a resistor in place of the switch. I tend to set the base idle up a little to a between 600-650 and you rarly have a problem.

[matbor]

reset the base idle, seems ok, away this week so will have to see if it is ok when i get back.

[matbor]

reseting the idle didn't fix it, it's erractic again !! Anyone have any more ideas ?

Actually I'm going to try resetting the idle again, just to see how long it lasts !!!

Matt

[shaunp]

Check the connectors to the Air flow meter are clean and if it is an auto you need to make sure the "in gear switch" is ok. If this is intermitent the car will idle low when in drive or reverse which can cause it to hunt uncontrolably. This switch makes the ecu lift revs to compensate for the load of the auto. Stalling in reverse can also be incorectly adjusted hand brake, if the idle is ok the rest of the time. When you cleaned the T piece did you also make sure the rest of the crankcase ventilation ie the port of the plennum chamber is free. Also ensure the vac advance diapram is ok.

[matbor]

Just changed the AFM, had a spare one... took it for a drive, seems to be ok, but this problem always seems to come back after a while, will try it out for the week, if it has fixed it I'll have to go and get it tuned again !!!



My question is has anyone replaced the AFM with an aftermarket one, and I assume you have to replace the ECU as well, what brand, setup and cost are you looking at doing this ? As this is the 3rd AFM, I'm thinking I might go for something a bit more reliable !!!

Matt

[LandyAndy]

Hi Matt
You could try speaking to the guys at JRT (Jordan Rover Tech) in Perth ph 08 93505633.
They do a lot of performance improvements to Disco/Rangie gear.They have fitted a "wolf" management system to a guys 110 V8 I know,havent seen him lately to get any info.
Im pretty sure they have a website but I no longer have the address.
Goodluck
Andrew

[matbor]

http://www.jordanrover-tech.com.au/

[shaunp]

Most after market ECUs don't use an airflow meter, they use MAP sense (manifold apsolute pressure)and or TPS only so you just chuck it away. In fact v12 jag engines work this way as well.

[bender]

I'm having the same problem, one thing i am about to try is to change the fuel filter,

[matbor]

tried that... you'll probably find it is either the air flow meter or the steeper motor, in my case it is neither !! Still haven't worked it out, going to go though and replace all the hoses next.

[matbor]

It's doing it again... new airflow meter (secondhand actually), and 4 weels later it is doing it again, what do people think about replacing the hose that goes from the plenum chamber to the AFM ? maybe it has a small pin hole, can't see one though.

Any ideas ?

[harry]

8) ok do you get the mystery rich running on slowdown after highway cruising?
8) harry

[matbor]

yes, but it will also happen to and from work, and that is in traffic, but only once the car has warmed up... Also it doesn't always happen !!

[harry]

8) its a small relief to find someone has the same disco virus,
it can be rather embarassing to have it flame out at the traffic lights just as they turn green.
yesterday i had to follow a bus down from o'reillys mountain, and with it stopping often to allow cars past, the disco began to rich up.
its almost like it drops a bank. finally it stopped and i was lucky enough to roll to a clearing.
getting going again is simple - just open the bonnet [why did the pomms put the cable on the left?] let the fuel pressure down by pressing on the valve then start it up
8) harry

[Patrick_M]

It can also be caused by the throttle butterfly position it's supposed to be a certain measurement (19Thou I think) leaning towards the plenum chamber in the direction to which the throttle turns, mine was always a problem so I adjusted it down reset the base idle and have had no problem since, the other reason could be that it (the butterfly) and throttle body needs a good clean out with carby clean. One more thing the throttle shaft potentiometer could be stuffed and sending all the wrong messages to the ECU, this I have found to be a problem as well.
Regards:- Patrick M.

[harry]

8) thanks patrick_m, i'll look at that soon.
8) harry
8)

[matbor]

That is one thing I forgot to add to the list (throttle butterfly position)... that got down about 20-30k ago !!

I wouldn't mind checking the fuel pressure next actually.

Matt.

[RANGEE]

i have a haltech E6X and was able to but my afm in the shed ... made me feel good extracting yet another lucas part from the RR... it runs better with the haltech and there is nothing blocking the airflow except the filter plus you can program the ECU as you like ... ( dont loose the original maps incase u stuff it up)
i have heaps of pics if anyone is interested...
cheers
RANGEE

[matbor]

Originally posted by RANGEE
i have a haltech E6X and was able to but my afm in the shed ... made me feel good extracting yet another lucas part from the RR... it runs better with the haltech and there is nothing blocking the airflow except the filter plus you can program the ECU as you like ... ( dont loose the original maps incase u stuff it up)
i have heaps of pics if anyone is interested...
cheers
RANGEE

Hi Rangee..... very interested in the pics, post them here or email them to me, PM if u need my email address, also interested in what you need to do to put the haltech in and what sort of cost is involved !

M.

[RANGEE]

ok so how do i post them here?
thanks

[bigbugga]

Originally posted by RANGEE
ok so how do i post them here?
thanks

You can load them into our gallery.

Or if you have problems let me know and I can do it for you.

PM me if you need too style_emoticons/<#EMO_DIR#>/biggrin.gif

[matbor]

How did u go with your pics Rangee...

Also has anyone else got anymore ideas ?

Matt.

[RANGEE]

yeah all good check out album 4 i think ... just put a few more in too ...
hope u all like ...
i strive to please ....
cheers
Rangee

[skids]

Just a couple of suggestions champ the fuel pump contains a non return valve which i found to be a problem in mine this may not be the fix but simple to check fuel psi running and not running.The other pos is you
could be chasing a non mechanical problem such as carbon build up in
and on intake runners,ports and intake valves i have carried out many
carbon flushes on engines with running problems with excelent results.
With the poor quality fuel they add PNA poly-nucular-aromatics to raise
the octane however the PNA seperates from the fuel once heated, this
happens as soon as the fuel reaches the fuel rail in the engine then passes
through the injectors which is then sprayed into the intake port where it
also hits the valve.The heat from the port and valve then turns the PNA
to a waxy residue which once cooled forms what we see as carbon.
This then causes running problems due to the carbon being like a spunge
it actualy absorbs part of the fuel being injected then becomes saturated
drips fuel and causes a rich,lean rich,lean effect.
look around for someone with a on car ultra sonic carbon flush should
cost around $175 good luck SKIDS style_emoticons/<#EMO_DIR#>/biggrin.gif

[harry]

8) thanks skids, as you say i also have had success with carby cleaner pressure pack, especially at the stepper motor and the hoses. also i found heavy buildup in the plastic t fitting where it t's into the throttle body and the plenum - there is a restrictor in the little tube which was blocked on mine.
i had a new stoppage problem last night which i think is the battery dying.
so if it gets me to battery world this morning they will get a sale, otherwise mr racq will win a sale!
i have fitted a fuel pressure guage to monitor that for a while, but have not driven in the same conditions that normally cause me problems.
and skids, welcome to the site.
8)

[matbor]

Would the ignition amplifier cause idle problems ?

[shaunp]

Normally causes missing and stalling at all speeds not just idle.

[incisor]

Originally posted by skids
J they add PNA poly-nucular-aromatics to raise
the octane however the PNA seperates from the fuel once heated, this
happens as soon as the fuel reaches the fuel rail in the engine then passes
through the injectors which is then sprayed into the intake port where it
also hits the valve.The heat from the port and valve then turns the PNA
to a waxy residue which once cooled forms what we see as carbon.
This then causes running problems due to the carbon being like a spunge
it actualy absorbs part of the fuel being injected then becomes saturated
drips fuel and causes a rich,lean rich,lean effect.
look around for someone with a on car ultra sonic carbon flush should
cost around $175 good luck SKIDS style_emoticons/<#EMO_DIR#>/biggrin.gif

we talking about rockets or landrovers..

[harry]

8) if mine doesn't improve it will become a rocket,
8)

[incisor]

my money is on the ignition module. but i fix puters not cars..