V8 idle stalling

Hi

My 95 3.9 efi v8 has a problem with cutting out when idling. It doesn't do it all the time and happens cold or warm, but more often when warm. When idling the revs will begin to rise and fall, until eventually they fall enough to cut out. The more load there is on the engine, e.g. headlights, sitting in drive (auto box) the more likely it is to happen. It starts again straight after. I have changed stepper motor, coolant temperature sensor, fuel temperature sensor, no improvement. Any thoughts gratefully received.

Hi

I've just got a 93 V8 ES with an auto box, I've had a similar problem but found that my engine usually drops it's rev's and stalls when slowing and then stopped facing up a slope.
Have also found that it'll drop it's revs when in reverse and stop.
My rev's on idle seam to vary depending if I'm in D,N,R or P.

Any thoughts equally appreciated.

I've not noticed mine is affected by slopes, it seems to stall in any situation, if it feels like it.

i recently had a problem with my 97 V8 not starting and also slight issues with tick over speed.

Found that the gap on the Distributer base plate and pick up arm was to great(air gap haynes manual called it).

Could always pick up the slack on the accelarator cable

Daz

Well guys, sounds like you need to get the spanners and DVM's out.

First some easy stuff - make sure your battery and alternator are good. Check the vacuum advance unit on the dizzy is working, check dizzy cap and rotor arm. Check for vacuum leaks.

Check readings to/from ECU for engine sensors.

A good thing to do is to take off the plenum and thoroughly clean it, check you air filter isn't blocked. Also check the throttle stop and operation of the throttle linkage. I know it sounds like a lot to do but it shouldn't take much more than a morning. Hope that gives you some pointers and good luck.

Also check the Base Idle speed, how to do that is in the book (Haynes manual). I have found that a spark plug change will make a differance (although I didn't change mine untill they had done 20,000 miles) so will a dose of petrol additive.

Thanks for those.
Battery and alternator are OK, have checked for vacuum leaks and can't find anything. I'll have ago at the distributor over the weekend. I don't think I've got the equipment to check ECU readings. Base idle and throttle linkages are OK. Might change the plugs if things don't improve, but they've only done about 9000 miles so I had intended to leave them a bit longer.

Your plugs should sill be ok if you don't have any missfire, how about the plug leads.

I have had the problem in the past on my ex RR and in the early days on the disco both times the dealers service dept fixed it and on the bill was 'adjust base idle'.

Something else to look at is the wire mesh breather on the rocker cover and the pipe from it to the plenum chamber they can get coaked up.

Have checked pretty much all of these and no real improvement.

Have a quick look at this, maybe it will help.
http://www.landyzone.co.uk/lz/623767-post2933.html

Do strip down the plenum and give it all a good clean. Set/re-set base idle. make sure your vacuum advance unit is working properly.

Good luck.

You may have a sluggish stepper motor,but more likely failing oxygen sensors.Have you done a really good check on vacuum leaks and also exhaust manifold/down pipe leaks ?

I had this problem on my 96 V8efi, on idle the revs would drop and then the automatic choke (i presume) would kick in and stop it from dying and push the revs up about 1000rpms, it would then start to drop again and the revs would just keep going up and down rhythmically, it would also stall say if i was driving along and slowing down at a junction and then put the clutch down - this wouldnt happen all the time but occasionally. I just tightened up the black thing around the accelerator cable - just turned it by hand - and put the revs at about 5/600rpm - since then after a slight bit of fine tuning (trying to keep the revs as low as pos whilst idling but without the wierd revvy thing happening -on petrol aswell as on LPG) all has been well, i know this isnt the ideal solution to the problem or even the proper 1 but i found it to be the quickest, cheapest and easiest! hope this helps

Tried most of the things suggested but no improvement. Eventually gave in and took it to local independent garage. Where it turned out to be failing air flow meter. Expensive fix, but it works.
Thanks for all advice received.