Weak revs, then it cuts out... ICV?

[AJC77]

Hi all,

Almost 2 years of trouble free running and I now have a brain teaser of my own :-) which goes like this....

After I've driven for half an hour or so and pull up at a red light or a junction I sometimes (not always) find the revs at idle go weak before the car then cuts out. No stumbling, no misfire, if anything the engine goes very quiet and the only check whether it's died or still turning over is the rev counter. It usually restarts ok although on one occasion it restarted but was still very weak before I gave it gas, selected first and got going.

Now yesterday when I started it up after a few weeks of not being used it sprung into life perfectly as it always has, as I left it to come up to temperature before driving (which I always do) it hit a point where the revs kept step changing from fast idle as normal during warm up to flat idle at full temp back to fast back to flat. It did this for a minute or two.

Now my first thought is to try a new ICV, before I part with £70 pounds of my hard earned has anyone else had similar, or do you have a different opinion to starting with the ICV?

Thanks in advance,

Andrew.

Ps it's the 2.9 thumper

[ukflyboy]

Sorry, but can't help with your symptoms as my ISCV has never even been connected since I've owned it! I do however have spare ISCV you could borrow and I'm not a million miles away (near Lewknor).

[GreenV8S]

I don't know how prone that ICV is to getting gummed up, but it wouldn't hurt to clean it. Although a sticky ICV can cause an erratic idle, any other problem causing the engine to run out of tune can cause similar symptoms. In particular, the engine will be very sensitive to air leaks at low rpm and low throttle.

[Barry S1]

I had a similar thing and it was the AFM, take it
off and give it a good clean up with carb cleaner,
worth a try and doesn't costs anything.

[PhilH42]

I had a similar problem when hot although mine was a 2.8 and it turned out to be a loose vac hose.

[glenrobbo]

Also had this on my 2.8 S1.
A 16mm vacuum hose had gone porous. I could actually increase idle revs by clamping my hands round it, and could also hear the difference in induction airflow noise.
I fitted a new hose and all was well.

[HvdWeerden]

AJC77 said:

as I left it to come up to temperature before driving (which I always do)

Can't help with your problem but warming up before driving is a bad habit, better to start and get driving to warm up your engine properly !

[greenhulk]

As the guys said possible air leak somewhere? Had this issue myself, it turned out to be a barely noticeable split in the rubber airflow meter cap aswell as the airfow meter plate inside was in a bad way & the rubber vac hose from servo to plenum looked abit worn.. This is what plagued my S the first time.

Also encountered this.. the car starts, leave it to get to 90, soon as the fan kicks in BOOOOM the car stalls, is your car playing up from cold start or when its warmed up to temperature?

Edited by greenhulk on Monday 17th October 16:40

[Alan461]

If the icv is working properly, the engine should nearly stall if the cable is disconnected.

[AJC77]

Thanks all!

It has only happened after a decent run and when thoroughly warm.

I'll start with carb cleaner on the AFM and ICV, and I'll check all the vacuum hoses which I might just replace anyway as it's probably good practice with ageing rubber.

Next question, any recommendations for knowledgeable folk (near Milton Keynes) who can properly check/adjust/set up the timing on the 2.9 Cologne? The age of our cars increasingly means knowledge of how to properly set them feels few and far between.

Thanks.