T4 Boost cut off!

[Alex121]

Thought I'd update this as I've finally got to the end of this annoying problem and I could only find one other thread with this issue, which had no solution.

After replacing most of the sensors that VIDA pointed too and doing numerous troubleshooting with Ashok via email, he stripped some of the sensors (ICV, MAP and VVT solenoid) off his T4 and let me borrow them.

I ran it all last week without any problems, given I was getting this issue daily on my sensors, one of his 3 sensors had fixed it.

We thought it was most likely the ICV, so yesterday I swapped his one back out and put mine in, 10 minutes into my journey this morning it's limping again.

Will replace it and update if the problem comes back but it's pretty conclusive now that the idle control valve was the problem

My cars done this on and off since I got it (4 years ago) and has got progressively worse, so I'm dead chuffed!

[Dazza007]

Ive got a P1, every now an then I get a similar problem. If I put my foot down in 3rd an 4th goin up the Rock Ferry bypass the engine completely loses power around the 3-4000 rev mark. It does this once, but at almost the same point on that road. Ive checked codes an get a P102 error. I checked my voltages from the MAF and Rufe says their lower limit is 2.2g/s but mine hovers around the 1.6g/s an occasionally drops to 0g/s for a split second. Tried another MAF but exactly same issue and readings. The only thing I see here is my engines boost went up to 1.7bar the other day, looking af this thread thats too much right? Torque says my bhp is 170 and 220nm torque so I am down on power. New Walbro fuel pump. Plugs, air filter, fpr. Anyone point me in the right direction here. My engine rings got replace at 83k an its done 130k now

Dax

[Alex121]

Just some info that may help with troubleshooting....

I replaced the MAF on mine after troubleshooting quite a lot and it made no difference.

I replaced my idle control valve with a 2 week old one from a friend and that sorted it - I thought! Then a few weeks later it happened again.

What it actually turned out to be was the front lambda sensor beginning to go.

I plugged it in ViDA and did a live PWM reading of the front lambda sensor. It should be pretty much in sync with the rear sensor (used as a CAT check) and should increase with the throttle being held - This wasn't happening on mine - See the video I shot.

https://www.youtube.com/watch?v=fEZdhheGWj8

I replaced the lambda sensor, reset the fuel trims (a must) and problem solved. MPG went up quite a bit as by this point it had pretty much completely failed and the front lambda sensor helps with the engine mix.

I do have a spare MAF now but unfortunately I'm pretty sure the P1 uses a different sensor to the P2. I would check your lambda sensor first if you can get the readings

[cheshired5]

Originally Posted by Dazza007

Ive got a P1, every now an then I get a similar problem. If I put my foot down in 3rd an 4th goin up the Rock Ferry bypass the engine completely loses power around the 3-4000 rev mark. It does this once, but at almost the same point on that road. Ive checked codes an get a P102 error. I checked my voltages from the MAF and Rufe says their lower limit is 2.2g/s but mine hovers around the 1.6g/s an occasionally drops to 0g/s for a split second. Tried another MAF but exactly same issue and readings. The only thing I see here is my engines boost went up to 1.7bar the other day, looking af this thread thats too much right? Torque says my bhp is 170 and 220nm torque so I am down on power. New Walbro fuel pump. Plugs, air filter, fpr. Anyone point me in the right direction here. My engine rings got replace at 83k an its done 130k now

Dax

If 2 known working MAFs have erratic figures, you have an air/boost leak not a MAF fault.

1.7 bar of boost is highly unlikely so be careful how you use and interpret Torque.
That was most likely the MAP reading.

Once again when interpreting Torque, don't think for one moment you'll get accurate power and torque readings so for problem solving, ignore them. In fact ignore them regardless. For accuracy, treat yourself to a dyno run.

[960kg]

^^^ as above Torque app is not to be relied upon for these accurately needed figures.

Sensors for P1 boost calculations is in the pic:

Nothing else affects calculation of boost pressure.

It is also never talked about but the rear O2 sensor not only reads the cat. but is necessary for good performance and final fuel trim.

Both should be replaced at the same time as they wear at the same rate otherwise you only gets the results of the weakest link!

[tommy t4]

Out of curiousty as mine has one, does yours have a MAP sensor?

[V40T4R]

@Alex121: how do you reset fuel trims?

[tommy t4]

Should have read early posts lol must have missed that,Keith right again!!

[Alex121]

Originally Posted by V40T4R

@Alex121: how do you reset fuel trims?

It's one of the parameters you can change/reset when you click in the 'Doagnostics' then 'Vehicle communication' tab in ViDA.

You should do this after every sensor/hardware change really as T4's are extremely fussy.

[V40T4R]

Originally Posted by Alex121

It's one of the parameters you can change/reset when you click in the 'Doagnostics' then 'Vehicle communication' tab in ViDA.

You should do this after every sensor/hardware change really as T4's are extremely fussy.

Needing a bit help here...so I believe selecting the ECM module, LTFT parameters should appear in one of the four tabs but can't....the tab "Programmed values" is grayed, is this normal? My VIDA version is 2014B!
Thanks for your input!