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Matt, Mechanical Engineer
Category: Toyota
Satisfied Customers: 22931
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a Toyota Avensis T4 GV05EPZ 2 litre. Engine No 1AZ-FSE/1660739. On

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I have a Toyota Avensis T4 GV05EPZ 2 litre. Engine No 1AZ-FSE/1660739.
On starting from cold it revs up to 2000 rpm, that's ok, but when hot it idles at 1600 to 2000 rpm still.
Toyota garage have checked the ECU, Throttle body been replaced, Manifold pressures are all OK. fuel filter been cleaned. Injectors checked. Exhaust readings ok.
Still not sorted. Any suggestions.


This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.

if the engine condition is the same then chances are the meter or the connection to it is faulty

Air leaks are very temperature dependent as gaps can open or close up as things expand with heat, so the weather and engine temperature can effect them.

This leads them to be quite intermittent in the case of mild leaks

its also worth cleaning the airflow meter by removing it from the car and spraying the exposed sensor wires inside the tube with a brake or switch cleaner - ensure that the cleaner is one of the old fashioned, non Eco type that does not leave a residue

On no account touch the sensor wires with anything physical as they are extremely fragile

Customer: replied 2 years ago.

I have now been told by the Toyota garage, they have checked for leaks already, the only thing not done is taking the exhaust manifold off and checking the gasket.

I have OK`d them doing that now.

If you think of anything else let me know.


Hello 1 other thing to try would be check over the pedal sensor for any problems, if they disconnect it the throttle should be be fully closed / in its idle position
Customer: replied 2 years ago.

Thank you Matt.

I had already thought of the peddle sensor. the garage says they have checked it. But we will see.

This car has been in the Toyota garage for 5 weeks, I am now getting to a point of last result.

Make me an offer and its yours.

Thanks again.

***** *****

5 weeks good lord no wonder you're losing patience with it the only other thing that occurs to me is a stuck open EGR valve
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