[MattiasRing]

Hi, I have a problem that comes and goes. The car runs fine 98% of the time but sometimes for no reason there will be no boost at all and the car is unresponsive but drivable. Most often it does not throw any codes at all and will resume to normal after a few minutes and especially if I let it just sit and idle. Sometimes it also acts up when at standstil for a few seconds.

It has happened twice now that it has given me a check engine light that give me codes for boost pressure and mass airflow sensor. If i use a scan tool to wipe the codes they do not come back immediately. Car runs fine when the check engine light is on as well.

I have searched around the forums for leads and from what i find many suggest changing the Map sensor and the air temp intake sensor as well as Maf sensor. For me this seams unreasonably expensive to just take a guess at what might be wrong instead of diagnosing the issue.

The car as stated runs fine almost always but it is very annoying when this happens and from what I have noticed it only comes around when the engine is up to temp.

The codes given are: 41ab and 3ff1

Info on the car:
Stage 2 remap
Dpf, egr and swirlflaps all removed
Runs an aftermarket air filter inside original box

(Setup has not changed since problem started)

Any ideas on where to start?

[Scubudo]

Make sure all of your boots are locked in. There is so little room between the motor and intercooler that it is possible that one could be loose and sometimes blows off but is still fairly well aligned and that they halfway reseat once there is no pressure. I once found 3 off them had done this and was wondering if had had just gotten used to the torque or if my performance was really down, because it still had a lot of power. IIRC I was also having MAF sensor warnings which didn't stop with a new sensor about the same time...but since they eventually went away, I stopped trouble shooting.

[POBEP]

In my case is was MAP sensor, just last month.

I got limp mode, lots of codes - none pointed to map sensor

Then I compared all codes conditions and noticed that MAP sensor was reporting the same value regardless of engine was running or not, under load or idling.

The ISTA has a test for it.

Plausibility check of charging pressure with exhaust gas pressure and ambient pressure.

The fault is detected if the difference between the charging pressure and the mean value from two reference pressures (ambient pressure and exhaust gas pressure) is above the limit value: -130 mbar

The difference between the reference pressures needs to be less than the following value: 150 mbar


The plausibility check is carried out when one of the valid operating ranges is active:

Engine in standby mode: Change in status from wake-up for at least the debounce time: 0.4 s

Terminal 15 ON:

- Terminal 15 on for the following minimum duration: 400 ms.

- Engine speed less than the following value: 0 rpm.

During after-run of the control unit for at least the following after-running period: 2500 ms.

Control unit voltage: 9.5 V to 16 V.

Or you can just monitor its absolute (not calculated pressure) value and see if it changes.
At idle or engine switched off its value should match ambient pressure sensor

if map appears to be working, then check for boost leaks & vacuum lines test.

[MattiasRing]

I did have a IC hose blow of on the cold side on the intercooler this summer but changed out the retaining clip and all was well.

What I have done so far is that I removed the Map sensor and gave it a good cleaning from all the soot and grime. I did also remove the Maf sensor and sprayed it with CRC maf sensor cleaning since it had some buildup of oil on the sensor. (I am guessing this is due to me running an oiled in filter). Since this I have had no loss of power so far and no codes but there is no telling it might come back here in a few days. If it doesnt come back I will go back to paper filters since the intake is not worth the trouble.

I will get the car up on my 2 post lift here in a day or two and look over the IC clips and hoses again just to make sure. I have also noticed just like how Scubudo mentioned that he “got used to the power” I sort of feel the same and just think it is due from me having stock intercooling hoses and the IC itself. Those leak alot and only get worse with more miles. Looking into getting an upgrade here soon.

Will update if the issue remains or if it was resolved with a simple spray.

[MattiasRing]

Also did run a test on my Icarsoft looking at the target value of boost/intake temp etc and the actual value and nothing seemed of. (This is when the car is running fine). I would for sure thing ISTA is a better tool and more accurate but from what i saw there was nothing wrong.

[MattiasRing]

I am re-opening this thread in hope that someone might be able to help with any insight.

The issue is still there and almost allways comes when I jave driven the car hard and can throw the same codes as above. I have replaced the air filter to oem and cleaned the maf again without luck.

The issue only comes on when the car is sat at idle after running to temp and usually gives no codes but give the issue of no boost pressure at all until i restart the car. Then it runs perfekt again, if the car however throws the code it goes into some sort of ”safe” map and has boost pressure again aswell.

If anyone had experienced anything similar im glad to listen or if you have any other suggestions.