can any of you good chaps help.my scoob has just started to idle funny.it only does it the odd time but i think its slowly getting worse.when i come to a junction or a stand still it idles up and down sometimes dropping to zero.it feels like its going to cut out.it only does it for 30 seconds ish and then sorts itself out.anyone shed some light on this.thanks.

 

MAF?
ISCV?
CTS?

 

first thing I'd do is clean the idle valve, it could be gummed up and not reacting fast enough to control ilde smoothly

 

What model year is it? Joz and Budd are on the money but knowing the MY would help us point fingers.

 

Mines doing this as well. when you plug the self diagnostics in comes up with a fault on idle control valve. I,ve cleaned it twice but still does it occasionaly. I've just bought a second hand one of ebay. hopefuly that will sort it as a new valve is nearly £300.

 

sorry chaps,its a ,w reg turbo 2000 wagon.what would you recomend i clean the maf with and is it an okay job,i know a little but im no mechanic.much appriciated.

 

or PLUGS

 

I thought you had got "bored with it"... Good to see you're still "on side" LOL

 

yeah i thought bout plugs.wot plugs would you recomend.

 

never get bore of that to the op........ i had very similar symptoms and i thought maf etc etc etc,ended up being the plugs.make sure they are gapped corectly before fitting as the majority supplied are not correct although they are supposed to be.

 

ngk,denso iridium etc

 

going to clean the maff tomorrow and just go through process of elimination.start with the maff as i can do it myself.what should the plugs be gapped at.

 

0.7mm

 

cheers buddy.ill have a little tinker with it tomorrow hopefully all will be well.

 

can you clean the maf ?

 

If you have a a MY93-98, yes. Best to remove the MAF and liberally squirt brake cleaner through it. Then hang it up in the airing cupboard or somesuch overnight,to fully dry it out..

Not sure if the MY99/00 are cleanable, as they use a very fragile hot film sensor I believe.

 

By and large the only people who benefit from people "cleaning" airflow sensors are the cowboys who profit from selling "MAF cleaning solution" (which is invariably water, isopropyl alcohol or brake cleaner sold at a bumper profit).

If you're running a good filter there won't, by definition, be anything big enough to be called dirt getting through to the airflow sensor so theoretically there's nothing to clean in the first place. If you are running one of the synthetic foam type filters (ITG etc) that comes coated with a thick "mucus", then there's no point cleaning a sensor that's been contaminated with that cr*p. It burns off on the element and once that happens no amount of squirting with solvent will shift it. Ditto a cotton element that's been over-oiled.

If you have an MY99/00, when these sensors start to go it's almost invariably nothing to do with contamination, the usual mode of failure is that the tiny wires which connect the sensing element to the circuit board fracture - and clearly no amount of cleaning will recover this once it's happened.

The wires are suspended in a silicone goo - so even though they're broken, they'll stay close enough to make contact some of the time, but not others so the ECU sees intermittent dropouts and under-reads in the sensor signal.

You can do a lot of damage to the engine very quickly if you drive hard on a sensor that is failing in that way, so the precautionary principle in this case is that when in doubt, it's better to replace rather than think "cleaning" will solve the problem.

The symptoms you are reporting are already consistent with the broken wire type of failure, and while there are other potential explanations, if you have already ruled out a dirty idle speed control valve chamber, the airflow meter is the likeliest suspect.

If so the best advice right now is not to take too long working through your process of elimination. Arguably better to buy another sensor immediately, fit it and reset your ECU. If the symptoms clear up, you know you solved the problem and you can pat yourself on the back for fixing it ASAP.

If the idle instability continues even on the new sensor, then you can take it out and put it on your shelf ready for the next time you need it. You can curse some bloke on the internet for the £100 you just shelled, but comfort yourself that £100 precautionary is much cheaper than the four figure number you'll eventually spend if you drive around for a while on a broken one.

One test you could try is that, the next time you catch it misbehaving at idle, switch the engine off, pop the bonnet, take the grey connector off the airflow meter, and then restart the engine. You'll see the Check Engine light. Don't drive it, but blip it a little and see what happens to the idle stability. If it's suddenly back to normal, you've found your culprit. Turn the engine off, reconnect the sensor and order the new one ASAP. Stay off boost til it's fitted.

Oh - and if someone pops along later and tells you of a test that involves unplugging the sensor when the engine is running, ignore them. They no doubt mean well but that test doesn't work, and has a nasty habit of passing seriously damaged sensors as good, which is the last thing you want in this situation.

 

very good info above as usual. i would personally put a new maf in for piece of mind,as i did.

 

its a uk my00,DONT CLEAN THE MAF!!