207 misfire under load

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Burt_100
OneWave
OneWave
Posts: 18
Joined: Sat May 06, 2017 9:52 am

207 misfire under load

Post by Burt_100 » Sun Mar 15, 2020 10:55 pm

Hi, sorry in advance for the long post I have a 2008 Peugeot 207 1.4 petrol that originally came in for the fan running all the time and the coolant temperature at maximum on the gauge, I traced that to a broken wire to the ect sensor and took it a test drive to find when at operating temp (90 degrees and above) it develops a misfire at 2000 -3000 rpm, The car didn’t have any fault codes and I carried out a compression and cylinder balance test which have both came up ok, the post cat oxygen sensor wasn’t reacting even when added fuel so I replaced it but it hasn’t changed, I smoke tested the intake and found a poor seal at the rocker cover so I revealed it and now I have a map sensor code P11AA, I have checked the wiring and all is good, I found a small amount of oil in the ecu multi plug but cleaned it and it didn’t return so don’t think it was causing the fault, I opened the ecu but there are no signs of anything untoward, The tips of the plugs and the tips of the oxygen sensors are white indicating a lean condition but it smells of petrol and is drinking it like mad, The only thing I have noticed is that the MAP desired value is between -50 to -60 Mbar but when I look at the actual it is 10mbar, I swapped the map sensor with a know good one and the values don’t change, has anyone any ideas on what could be wrong? What could cause a positive inlet pressure instead of a vacuum?

Iver
TwoWaves
TwoWaves
Posts: 117
Joined: Mon May 27, 2019 2:55 pm

Re: 207 misfire under load

Post by Iver » Mon Mar 16, 2020 2:22 am

What could cause a positive inlet pressure instead of a vacuum
?

Vacuum is created by the throttle plate in the closed ish position, once the plate is lifted then it will move towards atmospheric.

I would measure manifold pressure with an analogue gauge to verify MAP integrity.

How is the PCV on that ?

morriLinda1
Newbie
Posts: 1
Joined: Wed Mar 25, 2020 4:19 pm

Re: 207 misfire under load

Post by morriLinda1 » Wed Mar 25, 2020 4:32 pm

Burt_100 wrote:
Sun Mar 15, 2020 10:55 pm
Hi, sorry in advance for the long post I have a 2008 Peugeot 207 1.4 petrol that originally came in for the fan running all the time and the coolant temperature at maximum on the gauge, I traced that to a broken wire to the ect sensor and took it a test drive to find when at operating temp (90 degrees and above) it develops a misfire at 2000 -3000 rpm, The car didn’t have any fault codes and I carried out a compression and cylinder balance test which have both came up ok, the post cat oxygen sensor wasn’t reacting even when added fuel so I replaced it but it hasn’t changed, I smoke tested the intake and found a poor seal at the rocker cover so I revealed it and now I have a map sensor code P11AA, I have checked the wiring and all is good, I found a small amount of oil in the ecu multi plug but cleaned it and it didn’t return so don’t think it was causing the fault, I opened the ecu but there are no signs of anything untoward, The tips of the plugs and the tips of the oxygen sensors are white indicating a lean condition but it smells of petrol and is drinking it like mad, The only thing I have noticed is that the MAP desired value is between -50 to -60 Mbar but when I look at the actual it is 10mbar, I swapped the map sensor with a know good one and the values don’t change, has anyone any ideas on what could be wrong? What could cause a positive inlet pressure instead of a vacuum?

The cause could be in clogged cat. You should measure back pressure through hole for 1st oxygen sensor.

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