Previa Hunting On Revs

[yeoman43]

my k reg previa has this problem when everyting is connected. disconnect the throttle potentiaometer it runs perfectly but with a lot higher reves. any ideas?

[miti-babe]

my k reg previa has this problem when everyting is connected. disconnect the throttle potentiaometer it runs perfectly but with a lot higher reves. any ideas?

Sounds like you need to remove the throttle body and give it a darn good clean out (Haynes manual No. 2048, Chapter 4, pages 4-12 to 4-14 covers the entire procedure and also those of testing the TPI potentiometer. They recommend doing this every 60k miles - more frequently where the car is used mainly for short runs...

It's not an easy job and it's messy, but I found a massive improvement in engine stability and driveabilty after doing this and will definitely be repeatig the process every three years...

Good luck

Jeff

[Philat32]

my k reg previa has this problem when everyting is connected. disconnect the throttle potentiaometer it runs perfectly but with a lot higher reves. any ideas?

Sounds like you need to remove the throttle body and give it a darn good clean out (Haynes manual No. 2048, Chapter 4, pages 4-12 to 4-14 covers the entire procedure and also those of testing the TPI potentiometer. They recommend doing this every 60k miles - more frequently where the car is used mainly for short runs...

It's not an easy job and it's messy, but I found a massive improvement in engine stability and driveabilty after doing this and will definitely be repeatig the process every three years...

Good luck

Jeff

Is my problem related?

The car starts easily and runs well, until it gets to normal running temperature, then will intermittently miss awfully when the revs drop below 3000. It also idles like a pig whilst this is happening.

I have changed the distributor cap, rotor arm, plugs, coil and igniter, slight improvement but still there.

Help!!

[Ray99]

Hi Phil

Sounds like temperature sensor to me. When engine is cold a faulty temp sensor will not send a signal, the ECU assumes engine is cold and increases idle speed and richens mixture. When engine is hot the faulty sensor still says engine is cold so ECU is injecting far too much fuel. Hence the poor idle etc. The sensor is usually around the top hose/thermostat area and has a green connector. You will also benefit from a throttle body clean. Regards Ray

[Philat32]

Hi Phil

Sounds like temperature sensor to me. When engine is cold a faulty temp sensor will not send a signal, the ECU assumes engine is cold and increases idle speed and richens mixture. When engine is hot the faulty sensor still says engine is cold so ECU is injecting far too much fuel. Hence the poor idle etc. The sensor is usually around the top hose/thermostat area and has a green connector. You will also benefit from a throttle body clean. Regards Ray

Thanks Ray99.

Not having had a chance to fiddle with the sensor yet (damn work gets in the way ;) ) is it likely that the sensor could be showing an intermittent fault?

Is there any way of testing bar replacement?

Phil