Avensis Sr - Jerky/ Judderery Throttle At Low Revs

[womblesrevenge]

My girlfriend has a 2000 Avensis SR which has a really jerky throttle at low revs (2500 ish or below). Changing up or down gears it just judders and wont drive smoothly. (yes I have asked if it was just her and I have driven it myself as well!).

It has done 126k miles but does have full service history. Any suggestions anyone? I have searched the forums for similar problems and suggestions range from replacing HT leads/plugs to sensor issues. I had a similar problem on a mazda which turned out to be a throttle position sensor but just wondered if it could be the same?

Thanks for your help!

[Avensis luna 03]

My girlfriend has a 2000 Avensis SR which has a really jerky throttle at low revs (2500 ish or below). Changing up or down gears it just judders and wont drive smoothly. (yes I have asked if it was just her and I have driven it myself as well!).

It has done 126k miles but does have full service history. Any suggestions anyone? I have searched the forums for similar problems and suggestions range from replacing HT leads/plugs to sensor issues. I had a similar problem on a mazda which turned out to be a throttle position sensor but just wondered if it could be the same?

Thanks for your help!

I had a similar problem and it was the HT leads. To know if you have a faulty lead, take out the plugs and have a look at the porcelain. If you can see any black lines running vertically along the porcelain, then the HT lead is faulty. These will be very thin black lines and you will have to look for them but if they're in it you know what I'm talking about.

Hope this helps.

[womblesrevenge]

I had a similar problem and it was the HT leads. To know if you have a faulty lead, take out the plugs and have a look at the porcelain. If you can see any black lines running vertically along the porcelain, then the HT lead is faulty. These will be very thin black lines and you will have to look for them but if they're in it you know what I'm talking about.

Hope this helps.

Thanks for the response - I will have a look and see if this resolves the problem! B)

[Thomas Jorgensen]

My girlfriend has a 2000 Avensis SR which has a really jerky throttle at low revs (2500 ish or below). Changing up or down gears it just judders and wont drive smoothly. (yes I have asked if it was just her and I have driven it myself as well!)....

Is that model with the "lean-burn" engine? If so, I think it sounds like a defect in the "Swirl inlet control actuator". It is a common defect on these engines. A lean-burn engine has two different intake systems. The "swirl" system allows a leaner mixture, and thus better economy. However, the "normal" intake system is needed for low revs and high power.

If the vacuum actuator is defective, the engine is stuck in "power" mode . The ECU thinks it should be in Swirl (lean-burn) mode, but because it is not, the engine runs poorly and actually runs too lean and jutters. The ECU somewhat tries to compensate, but it doesn't work.

1) Check if the engine is actually lean-burn

2) Check if the vacuum actuator is placed on the intake manifold, either centered between middle cylinders or on belt side of intake manifold.

3) Check operation with warmed-up engine. Press accelerator until engine revs 3500RPM, and release. A movement of the actuator should be seen.

If indeed it's a lean-burn engine, and the acuator is not moving, you can find a replacement actuator or try and repair the original.

Regards, Thomas