Rav4.2 Sluggish Throttle Response And Pickup 1Az-Fe

[Joylove]

Hi Guys

Ever since I got our RAV4 with the cable operated 1AZ-FE 2.0 petrol engine, I've noticed it's very easy to stall when moving off in first.

I find you must blip the throttle to about 1500RPM before raising the clutch for a smooth getaway, which sounds like you are a boy racer at the lights. As on my other petrol cars if you raise the clutch and the revs at the same time, instead of a smooth takeoff, the car pretty much dies.

A clutch dip and a rev can cure it and suddenly the engine revs up to and the car leaps forward as I bring up the clutch.

It makes rapid movements very hit-and-miss, just when you need to car to go forward and get moving (eg at a roundabout) then the power dies away to none and you roll out into fast traffic, peddling at the pedals trying to get the revs up before bringing the clutch back up like some mad cyclist.

Noting; this is only when the engine is at the warm idle speed of ~700RPM. cold idle at ~2000 RPM is fine.

I always though it was because it's such a tinky-winky engine that it simply had no torque at ~1000 RPM and ignored it.

On then to my discovery of a technical 'problem':

I was sniffing about under the bonnet after a run at the weekend. With the engine running and fully warmed up, idling at ~700RPM, if I breifly jab at the throttle butterfly with my finger, instead of the instant blip in revs you would expect I get brief suction sound around the hot pipes at the throttle body area, a wobble in the revs, possibly an occasional backfire and then the RPM increases. I can open and close the butterfly about 20% before the revs start to go up as I jab at it with a finger.

It sound like a vacuum is built up, something snaps shut under that vacuum and then the engine picks up. It is this delay in butterfly movement -> engine pick up that causes the engine to almost die as I bring up the clutch and bring down the accelerator.

Any thoughts on what it might be? A hose collapsing? A bypass valve that's old an slow?

The car servicing is up to date, the O2 sensors are fine and recent, the filters are recent, the ICV is cleaned, the Throttle Body is cleaned, the accelerator cable is correctly adjusted.

EDIT: Here are some videos. The first is the car on choke and warming up. There is a largely instant response to a jab of the throttle. The car quickly comes off choke (love how fast these cars warm up) during the video and the idle speed drops down, ending the demo.

In the second video the car is mostly warm. A jab of the throttle is met with a suction sound, some delay, and finally a generally late and wobbly in increase in the revs, and this is the point where I am almost stalling as I pull away. As the camera moves in closer to the approximate area of the suction sound, please forgive my wife's yawn...

Sorry about the late evening shadows in the video. My hand goes directly to the throttle butterfly and back.

Thanks :D

[igormus]

clean MAF sensor and try again

regards

[Big Kev]

clean MAF sensor and try again

regards

Igor beat me to it, Bob, but are your spark plugs deffo iridiums....? (If that's the spec.)

Big Kev

[anchorman]

It should have Iridium plugs and just take the inlet pipe off the manifold to take it out of the equation. They do tend to lag a bit if you blip them like that.

[anchorman]

It should have Iridium plugs and just take the inlet pipe off the manifold to take it out of the equation. They do tend to lag a bit if you blip them like that.

[Joylove]

Yep it has iridiums and I cleaned the MAF today, it was pretty black. I pulled the Battery to clear the adaptations so will take it for a run as soon as I can. Inital impressions are that the cold idle has dropped from 2000RPM to 1500RPM and the lag is less. I'll wait till I've clocked up 100 miles before I'm sure but first impressions are positive. Muchos Gracias!

Still want to find that hissing. Appears to be from the ICV, which I have a new gasket on so it shouldn't leak.

[Joylove]

Took the car out today, much improved with the cleaned MAF. Thanks very much chaps and especially Igor. :D

[Uncle_P]

As something of an amateur ,how do I get to the mass airflow meter, and what do I clean it with? Does it come off easily, or is it cleaned in situ?

[anchorman]

Better still, did he take photos so we can pin it???

[Joylove]

...

[Joylove]

I didn't get any pictures but there are a few online.

The MAF is located on the top of the airbox near the firewall.

It has a clip on connector and two cross head screws. It is necessary to remove the two bolts that hold the airbox to the engine, and remove the jubilee clip for the air hose so you can get a screwdriver to the screws. This pic is a Corolla I think but the MAF is the same as the RAV4.

Take time to make sure your screwdriver fits the screw head perfectly, they are easy to round off the heads being rather soft metal.

The MAF has both a bead thermistor and a couple of hot wires. Both will be blackened.

I used IPA (Isopropyl alcohol) to clean the sensor. You could try meths, carb cleaner, PCB cleaner or even petrol. Anything that evaporates and that won't damage the plastic (thinners, white spirit are a no-no). To get down to the hot air flow wires is the most important part, and for this I used a cotton bud Q-tip thing.

The wires are just that; wires. Don't bend them, don't snap them. Work gently. Once cleaned they will change from black (as shown above) to silver.

Disconnect the negative from the vehicle Battery then reassemble. This will clear your adaptations. Expect rough idle and high MPG for the first 60-100 miles as the engine relearns the new adaptations.

[igormus]

Took the car out today, much improved with the cleaned MAF.  Thanks very much chaps and especially Igor. :D

enjoy driving, thengood luckIgor