2010 ford mondeo 163 titanium x - manifold pressure feedback

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Tue 24 Nov 2015 12:48
2010 ford mondeo 163 titanium x - manifold pressure feedback - MartinL

Hi Guys,

I have an intermittant amber warning (Engine malfunction) which does not show on restart. I have no fault codes appearing when interrogating the ECU and the engine runs normally whether the fault indication is present or not. The only thing that does not make sense is the feedback from the manifold pressure sensor when the engine is static. The reading is -0.8Hg.this is a significant vacuum reading with engine at a standstill. Is this normal or is the sensor faulty?

Best regards and thanks in advance for any info.

Martin

Reply | Report as offensive | Link
Tue 24 Nov 2015 12:53
2010 ford mondeo 163 titanium x - manifold pressure feedback - hardway

Best guess,

and it is a guess is thats low,

at idle,

petrol engines at idle have a much higher vac reading than that,

I've seen readings of 14.5 hg.

Reply | Report as offensive | Link
Tue 24 Nov 2015 13:29
2010 ford mondeo 163 titanium x - manifold pressure feedback - MartinL

Hello Hardway,

The engine is not at idle but in fact not running at all showing this reading.

Reply | Report as offensive | Link
Tue 24 Nov 2015 13:07
2010 ford mondeo 163 titanium x - manifold pressure feedback - Railroad.

I'm not entirely sure what you're reading but a normal vacuum for a petrol engine at idle is around 20 inHg. Make slight adjustments to this figure to allow for your height above sea level and differences in barometric air pressure.

Your car's ECM doesn't usually read 'inHg'. It reads in KPa. 100KPa = 1 Bar (14.7psi) which is atmospheric pressure. At idle your manifold pressure should be around 40KPa

Reply | Report as offensive | Link
Tue 24 Nov 2015 13:31
2010 ford mondeo 163 titanium x - manifold pressure feedback - MartinL

Hi Railroad,

The motor is diesel and not running when the reading is taken.

Reply | Report as offensive | Link
Tue 24 Nov 2015 13:42
2010 ford mondeo 163 titanium x - manifold pressure feedback - Railroad.

Hi Railroad,

The motor is diesel and not running when the reading is taken.

Then put your vacuum gauge back in its box. Diesel engines do not have a throttle butterfly valve, and therefore no manifold vacuum.

The MAP sensor in the case of a diesel tells the ECM turbo boost pressure, and with the engine not running should read atmospheric pressure.

Reply | Report as offensive | Link
Tue 24 Nov 2015 13:48
2010 ford mondeo 163 titanium x - manifold pressure feedback - craig-pd130

Have you tried removing the pressure sensor and cleaning it? As it's so close to where the inlet trunk from the intercooler meets the manifold, it gets covered in a) oily residue from the intercooler trunking, from the small quantities of oil that's wept past the turbo seals and b) sooty crud from the EGR pipe.

It's definitely worth removing, giving it a good hose down with carb cleaner, and refitting.

Reply | Report as offensive | Link

Looking for a garage you can trust? Honest John's Good Garage Guide has thousands of reader recommended garages, plus how-to guides and tips on servicing.

The Good Garage Guide