MAP Sensor problems

[parich]

Hi All,

I have a Toyota Avensis D4D T180 2.2 an have a problem with smoke and lack of mpg

I used to get 40-45 mpg up until a few months ago ... I now struggle to get 30 mpg on a long run.

After increasing power after idling --- at roundabout or traffic lights I get loads of white smoke (smells of diesel) ... which eventually calms down after getting up to speed (very emabarrassing!). I don't seem to have any drop in power.

I had a diesel specialist take a look and the only think he could find was an issue with the MAP Sensor (this was reading 70kPa when disconnected ... he reckoned it should be reading 100kPa (atmospheric). The sensor was picking up changes in the turbo presssure as the engine is revved.

I've checked the usual suspects, EGR valve, Air filter etc ... but I'm a bit stuck now. Mr Toyota want's £300 plus vat for a new MAP sensor ... I'm a bit reluctant not knowing it this is the fault

any ideas? or inspiration?

[stevieturbo]

SO this "specialist" said he thinks the map sensor is at fault because it reads 70kpa when disconnected....there's a huge clue there.

But it works as expected when connected ?

Maybe it's just me, but I would expect odd readings when you disconnect a sensor....simply because it isnt connected to the ecu anymore !!

Save your money and find a better garage to diagnose it. I certainly wouldnt be buying a map sensor based on that diagnosis though

[parich]

when I say disconnected. i mean from the manifold .... it is still connected to the ECU, the ECU is where the reading was being taken from via diagnostic software...

He said that the 70kPa seemed too low when the engine was not running. disconnecting the vacuum tube showed that the sensor was reading atmospheric pressure as too low (it should have been around 100 kPa). His theory was that too much fuel was being fed in at low revs.

[stevieturbo]

parich said:

when I say disconnected. i mean from the manifold .... it is still connected to the ECU, the ECU is where the reading was being taken from via diagnostic software...

He said that the 70kPa seemed too low when the engine was not running. disconnecting the vacuum tube showed that the sensor was reading atmospheric pressure as too low (it should have been around 100 kPa). His theory was that too much fuel was being fed in at low revs.

That makes more sense. Yes it should be reading in the region of 100kpa when key on, engine off

How was it reading with the engine running ? I assume he tested it against a manual gauge to see if it was wrong everywhere ?

Did he test the wiring from sensor to ecu etc, to ensure it was in good order ?

[parich]

He tested with a manual pressure gauge and said the manifold pressure was fine ....

When running the sensor does show changes .... the voltage output from the sensor also looks ok ... as per toyota spec.

that's why I'm so confused ...

manual test shows pressure ok...

voltage test shows sensor ok.

[stevieturbo]

It does sound like a bit of a contradiction, unless something got lost in translation somewhere.

You could try phoning around some breakers to see if you could get a second hand unit. £300 is a fair whack for a new one !