erratic idling 1992 3.9 efi RRC

Hi all,
Just recently,I have been experiencing erratic idling and revs racing on my 1992 RRC v8 efi ( pre-cat).
When I start up from cold or hot, the engine imediately races up to about 2000-2500 rpm for a few seconds, then comes back down to normal tickover. This has the added effect of switching it over to gas straight away !Then when driving along (with engine at normal running temp.), when I pull up at lights or junctions and have to wait a while, the tickover drops slightly then returns to normal.Sometimes if I rev it slightly upto say 1500rpm , it stays there for a second or two after I take my foot off the pedal.
I have also noted that it now takes a couple of cranks to start from cold now , whilst for the last 2 and1/2 years of ownership , it has always fired up virtually on the button ! I have replaced the sparkplugs with no improvement in start up time.When the engine is warm , it starts on the button.
Any help gratefully received.

The idle is likely to be the idle control valve or it's surrounding pipework. A good clean sorts out most problems, but often the valve needs replacing too.

As for the startup, no idea, but mine is the same now. Went out laning recently, when I got back it now spins over for maybe 2 seconds, sometimes more before starting, but of recently started then its crack on like normal.

Makes me think lazy fuel pump but doesn't really make sense.

Anyway cheers

All standard suff, you can replace the By-pass air valve (stepper motor) if you wish and reset your base idle but first I would clean the crankcase breather and its tube to the plenum and also put injector cleaner in the fuel.

Standard stuff as over the years I have had similar issues and a breather clean and fuel treatment worked

As for starting mine as always cranked over four or five times when cold before starting it's only two seconds, the delay is all about the ECU waking up and signals from or to the fuel pump I believe (i'm not that interested). I can't remember what happened in my 3.5 days but I suspect the starting was just the same.

It's just weird that mine has changed its starting habits after 2 years off roading and it's been the same. But yeah it's all about timing and it still starts fine WHEN it gets round to it

What i've seen on V8s is the engine bay suffers from a lot of condensation in the cold mornings the exposed metal of the bonnet is dripping also rocker covers and important parts like leads and coil are dampish but still starts though but if i had iffy leads it wouldn't thats for sure.

Thanks all.I am off work now for christmas so will try the crankcase breather /injector cleaner first. The funny thing is that it has only done 193000 miles !!! Seriously though , don't the injectors stay cleaner when running on gas , which it has been for the last 10 years !

Had a look around the engine bay and found a split in the vacuum hose where it pushes onto the drivers side of the plenum, and where the vacuum hose pushes onto the distributor , the assembly was loose which required a torx driver to tighten it up.This has resulted in an improved start up with the revs not racing up now. I also charged the battery up , which has improved cranking speed and therefore it fires up quicker again ! Thanks , and happy new year to you all.

well done, the same happened to me

i have an intermittent start fault with an 87 range rover efi automatic. it occurs after a heavy downpour- which, in edinburgh-will become almost every other day. i bought 2 weeks ago- and during the dry weather- it started with a singke turn of the key. however, the last few days has seen the rain come along, and now these starting problems. i remember i had a '91 240 estate 2.3i, which was very similiar in wet weather, until i changed the fuel pump relay- never had rainyday blues again afterwards. can anyone tell me where the relay switch is kept? and if it's easily accessible by a novice? or any other advice on tackling the problem d.i.y. style, many thanks & happy roving, russell

Relay switch? IIRC the fuel pump and efi relays are under the drivers seat on a 1987 3.5 RR.

And :welcome2: to the Forum.