Idle Air Control Valve

[pgp001]

I had a problem yesterday with the idle speed dropping right off and actually stalling the engine at junctions and roundabouts. In the six weeks I have had the RAV it has never done this before and it seems to be intermittent, yesterday it did it quite a few times, today it behaved normally.

After much searching on the internet, I reckon it must be the idle air control valve sticking, but I cannot tell exactly where it is on my 2004 car.

Most of the information and photos only show the previous models which used a cable controlled throttle body, mine has no cables just a motorised butterfly valve in the throttle body and I presume a throttle position sensor. The Haynes manual has an arrow pointing to an IAC valve, but it is not very clear on the diagram where it is.

So does anyone know if it is built in to the main throttle body, and if it is can it all be stripped down and cleaned out properly. Or is the IAC valve mounted somewhere else on its own ?

I have pulled the air filter and its hose off the throttle body and given it a good squirt of Wynns Fuel Injection Intake & Carb Cleaner, it was fairly black down there. I have my doubts as to whether I will have got the IAC valve with it though.

I am wondering if I should order a new throttle body gasket, and pull the whole thing off the car and try to strip it down for cleaning, but common sense is telling me to leave it alone and see how it runs for a while now I have sprayed it.

Any Ideas please ?

Phil

[IanXT4]

The Haynes manual is useful, but I have found it a bit basic for all the variations of the RAV. The best source of information is Toyota Technical publications site.

http://www.toyota-tech.eu/default.aspx

You have to register and they charge 3 Euro's per hour (plus VAT) but you have access to the official technical publications for your precise model. I visit the site when I have a problem, download what I specifically need, then spend the rest of the hour downloading other useful info. The only problem I found is you have to spend ages naming everything afterwards so you can find it all again :-)

With regards to your Idle problem, looking at the engine control system for your car (which is attached) its not fitted with IAC valve. I think IAC valves are only necessary when you have a cable throttle. With a motorised throttle you can adjust the idle directly.

In the attached document it suggests that the throttle flap position is rigorously monitored and failure causes the engine to go into limp mode (which I suspect would trigger the engine warning light).

I therefore don't suspect the problem is in the throttle body, my first guess is its probably a dirty (or faulty) air flow meter. I think the AFM is easy to remove and clean. However, they are very delicate/sensitive and your cleaner must not leave any residue. Personally I would use http://www.maplin.co.uk/isopropyl-alcohol-28994 or something specifically designed for this type of sensor.

Any advice given is meant to be helpful and in good spirit. No liability is accepted for loss , damage or injury. WORK SAFELY

Sensors and ECU.pdf

[pgp001]

That's brilliant, just the sort of answer I was hoping for thanks.

I will not waste any more time on the throttle body at this stage if it does not have an idle air valve in it. I thought I was cracking up not being able to locate it, but if it doesn't have one I don't feel so bad any more.

As I already mentioned, yesterday I gave the throttle body a good dose of cleaning spray which shifted loads of black sooty deposits from around the butterfly.

Before I did this the normal idle speed was about 700 rpm but the strange thing is that when I got it all back together after cleaning it the idle speed was up at around 1200 rpm even when up to running temp. I must admit I was beginning to wonder if I had made it worse !!

So this morning I set of early and drove around for a good half an hour to get it fully warmed up, and by the time I arrived at work the idle speed had settled to a steady 900 rpm.

After the 15 minute run home this evening it is now idling at around 780 rpm, so it seems to be gradually dropping to near normal with each use.

Am I right in thinking that the ECU is now "re-learning" the correct settings as I am actually using the car ?

Should I have actually pulled the ECU relay, or disconnected the Battery to re-set it and make it forget everything ?

Anyway so far so good and it has not done its stalling trick at all today, I am still a bit sceptical though, and am waiting for it to catch me out again.

So I have ordered a can of CRC spray cleaner which is specifically designed for cleaning the MAF. If it does it again I will try that next, but until then I am applying my golden rule of "If it ain't broke, don't fix it"

Thanks again for the information and link to the Toyota site, that looks really useful.

Phil

[IanXT4]

Glad you found the information useful.

I don't believe pulling the ECU fuse is going to affect your idle speeds. I have disconnected the Battery many times and noticed no significant difference in engine operation afterwards.

My suspicion/guess is that your air flow meter is very slightly contaminated. At high air flow rates its probably not affecting much, but at idle speeds when air flow is low, maybe the error is just enough to throw things out.

If you used a lot of carb cleaner, some of the evaporating alcohol might have found its way to the air sensor causing the changes in idle speed you saw today.