RAV4 2001 1AZ-FSE Hesitation - Solved

[Ronkey]

Hi All

My wife owns a Japanese Import 2001 5 door RAV4 manual with the 1AZ-FSE engine. It came to the UK about 2years ago and had done an almighty 65k over 20yrs. As you might imagine, the car was immaculate. The underside had no rust whatsoever (the exhaust flash rusted in about 3 weeks) so I was quick to underseal to preserve the condition.

However, it was quickly apparent all was not well. The car suffered from hesitation at a constant speed which on a carburettor engine I would have attributed to it running lean. As a first step, I replaced all the EGR seals, cleaned the EGR, new throttle housing gasket, new inlet manifold gasket and a new oxygen sensor. This did result in some improvement to running, but I was not satisfied.

After several weeks thinking about this, I decided to check the condition of the inlet valves and swirl valves (between the inlet manifold and the head). My logic was that as the 1AZ-FSE is a direct injection engine the inlet valves do not see any fuel to keep them clean. I had also noted in step 1 that the EGR was quite dirty. I found that the inlet and swirl valves were covered in black gunk.

To help anyone who may have a similar issue, there are two bolts hidden on the back of the engine supporting the inlet manifold. They are a pig to get at and tight. Once all bolts have been undone from the inlet manifold, remove the swirl valve for cleaning. Don't bother trying to lift out the manifold itself: it will not fit! Instead push it down to gain better access to the inlet valves.

Cleaning the inlet valves were a nightmare: I needed a mirror just to see. Make sure the valves you are cleaning are closed and that the other ports are sealed with a cloth or similar. I used every trick I could think of: toothbrushes, a brush kit for a Battery drill, screwdrivers, air compressor, solvent and many, many cloths. Get all the carbon out before starting on the next cylinder then seal.

I am sharing this because it worked and took me a good few months to work out. I hope it will be of use to someone.

Oh and I had no success with the cleaning fluids that you spray into the air intake. Save your money.