1.8 Duratec.  Couple of weeks ago thought I felt a misfire, under heavy load.  Thought nothing of it.  Friday night, I'm heading away on a 200 mile trip and again, a misfire, under load.  Not so much a misfire, more like what you'd expect if you turned the ignition off for an instant then back on, total loss of power.  Not like a coil pack where you'd still expect some pull from the 3 cylinders that aren't missing.

Virtually undriveable today, disconnected EGR (EML eventually came on) with no difference to the loss of power.  Got forscan on my phone, finally notice that while monitoring the MAP sensor, voltage is dropping from 4v to 1.6v when the loss of power occurs.  As soon as voltage goes back up to 4v, car pulls like a train again.  Totally random this.  Even wiggled the feed lead to the MAP sensor but no difference.

Also in forscan, unsure if this is the correct way but, to eliminate the 5 volt feed, decided to monitor the cooland temp sensor 5v feed and the accelerator pedal position 5 v feed.  None of these voltages drop when the car cuts out.

What do you think, if you having a read?  MAP sensor?  Also, is the wiring from PCM to 5v feed on MAP loom independant of the coolant temp / pedal position 5 volt feeds or do they all come off the same rail?

Any ideas, thanks in advance.  Just put tyres on and taxed it so need it going for next weekends big trip.

cheers.

So I just fitted another MAP Sensor and been on a quick 30 mile test run.  Car hasn't missed a beat so I'll close this thread.

Here is a link to the full Wiring Diagrams for your car that were kindly posted on this Forum by a member  

I'm not sure if the Voltage you were monitoring was the Feed to the MAP or the Feedback Voltage, I would normally just look at the actual MAP values instead which should be meaningful if you also monitor the Accelerator Pedal and Throttle position as well. The MAP should increase with an increasing APP. 

 

@Tizer  Many thanks for the link.  I should really credit @TomsFocus for my earlier rough running thread as I thought it was the runner control solenoids that were the problem but they only masked what was really on its way out.  The MAP sensor.