RX300 woes - cannot be coincidence?

[rickpriceuk]

Folks,

Need some help. We have a 2003 RX300, 175k miles. A few weeks it starts running rough, not allowing revs to go above 3000rpm and generally spewing out loads of fumes. It also loses the outside temperature reading, on the same day - reads '--'.

The local garage say the two are not related, and that the error code reads AFM sensor. They replaced this to no good effect.

Specifics:

1. Will not start on first turn but does thereafter

2. Runs very rich

3. When you try to rev over 3000 it feels like a major misfire

4. Outside temp not reading

5. No power to outside temp sensor

6. Sensor resistance does change with hot & cold water so probably not the sensor itself.

7. The fuses under the bonnet all look OK - are there any others?

 

Any help and advice would be gratefully received.

 

Many thanks,

 

Richard

[rickpriceuk]

Anybody got any clues, by any chance? Otherwise the car is off to car heaven soon.

 

Many thanks,

 

Richard

[Coxy]

Hello Richard,

I've a fair history in mechanics so this is based on my experience with engines in general and not specifically related to an rx300 but a lack of wanting to rev out along with your comments of running rich (what makes you think this?) leads me to suspect an air leak or a sensor that controls fuel/air (one or both) failing. Alternatively it could be spark related. Have you pulled the plugs?

Sensor wise we could have failings of :

MAF, (easy to find, on top of air filter pipe housing)

Lambda (oxygen) sensor, (usually located post manifold in the exhaust outlet)

Map sensor (possibly not present on RX300 due to age)

 

Deeper issues could be injector failing or coil failure (actually easy to fix)

From what you describe I do not believe outside temp fail would be related to your running troubles but who knows what sensors/stuff runs on the same sub looms as that (in essence nothing would surprise me with modern cars).

 

Hope that helps prompt some further investigation in the right places