Damn car just started acting up.

As soon as it speeds up, it loses all it's power.

Just listening to it as I raise the revs, there is a deep erratic sound like 'hammereing air' (whop-whop-whop), and the engine is wobbling erraticly in the bay. Not even smooth on idle.

I'm assuming it's some asperation or fuel supply problem...

Any common issue to cause this?

 

You sure it's not misfiring? I'd check plugs and coils before I dug any deeper

 

If you're not getting a check engine light and codes to read, the next thing you need to check is fuel pressure with an appropriate gauge and connecting hoses. Don't ask me where to buy them, I made mine from factory hoses.

 

SOLVED!

There were no check engine lights, and the first thing I did was check and clean the spark plugs and coils. This didn't make any difference.

So I went on to check the air filter - it wasn't too dirty, so I continued down the line and took out the air flow meter. it looked OK, but when I removed it, there was some debri between it's intake mesh and the air filter - wasp carcasses etc. and I heard a leaf* fall out and scuttle down through the engine bay. At the time I thought nothing of it - some muppet had obviously been careless when replacing the air filter, and let crap fall into the line.

I decided to swap in the air flow meter from my dads X300, and what do you know, the car runs perfectly. Oh hell, thinks I, seeing the 700 quid price tag on a new air flow meter.

Anyway, I couldn't help but try my air flow meter in my dads car just to be 100% sure it was fault, but the damn thing worked fine. No I was confused.

*Then I remembered the leaf. I hadn't even seen the thing, so I guessed what size it would have been, and made a replica leaf out of masking tape. Sticking it to the intake mesh of the air flow meter, I fired up the car, which promptly chocked to death. I moved the masking tape leaf down to a lower position on the mesh, and the car idled, but would not rev properly: just like the original fault. In some positions, the masking tape seemed not to affect the car at all.

More repositioning of the masking tape confirmed it: The phantom leaf had been the culprit. It hadnt been blocking the air flow to the engine, but rather changing the aerodynamics of the tube feeding into the air flow meter. This was confusing the air flow meter, and making is send false information to the computer, which stopped the car from running properly.

Moral of the story: Be careful when you service your air filter, and ensure that no engine bay rubbish falls down behind it!