Thread: erratic idle

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

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

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

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.

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

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

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.

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