Technical Poor performance Bravo 1.6 MJT

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Technical Poor performance Bravo 1.6 MJT

orndahl

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Subject:
Bravo 1.6 MJT with DPF, MY2011, 97.000km. Serviced according to plan.

Symptoms:
Sometimes when accelarating during low gear engine looses power on and off and starts to "jerks", usually between 1500-2200 RPM. It´s been going on the last 15000km or so and I´ve adapted my driving to "work around" it so to say. But now i feel it´s becoming an issue during over taking.
Engine management light has never come on and no error codes stored in the ECU.

Solution:
Google suggests EGR valve, said and done, new one fitted without any change to the better.

Trouble shooting:
Hooked up MultiEcuScan while driving to work to monitor and log these values;
"Engine RPM"
"Desired Boost Pressure"
"Boost Pressure"
"Desired EGR position"
"Actual EGR position"
Angle of approach was to see if i was getting the boost the ECU is calling for and if the EGR is closing. Acceleration was done both with full throttle and less to see how the EGR valve is behaving. I´ve attached one screen shot but they look very similar during the entire log (100km)

Result:
When looking to the graph one can see that first acceleration performance perfect. Engine is getting the boost the ECU i calling out. During second acceleration the pressure is not building up as the ECU wants and the ECU starts to regulate up and down (cars starts to jerk). When the engine hits 2300RPM the pressure builds up and hits the target.
During this time the EGR valve is closed (true position) altho there is a small delta to "Desire EGR position"

Second graph show same situation but with OK performance, even accelerating from low RPM´s.

Conclusions:
New EGR valve is faulty
Stuck/sticking waste gate
Faulty pressure sensor
Faulty regulator valve for wast gate (is there any?)

Sorry for the long text but I´m looking forward to some good input from the Bravo experts (y)
 

Attachments

  • Fiat Bravo graph 1 NOK.PNG
    Fiat Bravo graph 1 NOK.PNG
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  • Fiat Bravo graph 2 OK.PNG
    Fiat Bravo graph 2 OK.PNG
    70.2 KB · Views: 65
Last edited:
Two actions required:
Clean the MAP= boost sensor
Remove the turbocharger and clean the waste gates
You will find a lot of sticky buildups on both elements
 
Mine started to misbehave something like this recently. It seemed to get disorganised when I pulled away in 2nd. I did a forced regeneration of the DPF and normal service was restored. This takes 10 minutes and the relevant software to perform or a trip to Fiat but for diagnostics prepare to be ripped off. I use Gendan.co.uk software which seems to deal with nearly everything
 
OK, problem solved :slayer:
Went for a drive and logged the boost pressure as well as solenoid valve for waste gate and saw that the valve was acting a bit strange during moments of power loss.
Checked DPF status with MultiEcuScan: 77%
Checked that the waste gate arm was moving freely:OK
Checked pipe work and vacuum lines from and to solenoid valve:OK
Changed solenoid valve: Problem solved

Much better overall power >2000 RPM and no hesitations what so ever.
 

Attachments

  • Fiat Bravo graph 5 NOK low RPM.PNG
    Fiat Bravo graph 5 NOK low RPM.PNG
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