New AFM blowing black smoke?

[-=HaZ=-]

Hi Guys,

I recently noticed that my car was hunting when idle after the sensors had heated up. Speaking to my mechanic and also reading on this forum, it seems the AFM was at fault. This made sense as unfortunately the VF38 turbo recently failed; I have an MY06 BL Liberty GT Tuned by STi. At the time of the failure, allot of white smoke (oil) was blown back through the turbo and forward onto the AFM.

I am not the original owner, and whilst the service history seemed sound, I have been told that a lack of servicing can cause premature turbo failure. I service my car every 5000km's so I am sure I didn't add to the premature failure of the turbo.

So after sending the VF38 housing to GCG Turbo and having it machined out to install a VF34 ball bearing core into the VF38 housing, retaining the twin scroll setup etc, I had the new turbo fitted and made preparations to have it tuned at Chip Torque on the Gold Coast. As I suspected the AFM was on its way out and I wanted the best tune possible, I ordered a new AFM geuniune DENSO OEM Part Number: 22680-AA310 / 197400-2090. In the meantime I drove around with the new turbo, on stock boost, the car drive very nicely, I noticed that even with the stock ECU tune and failing AFM the car felt very responsive and new that the new turbo was doing its job.

Wanting to fix the hunting problem before it got tuned etc, I decided to fit the new AFM myself tonight, a simple matter of unscrewing two screws, disconnecting the harness plug and installing the new AFM part. HOWEVER as soon as I installed the new AFM, the car choked and spluttered, wouldn't rev and continuously belched out black smoke! Now I know black smoke means its running very rich, so much so that the car was undrivable.

Could I have a failed AFM on my hands or could the new very sensitive new AFM be reading heap of new Air Flow from the bigger, turbo over fueling to compensate??? Keeping in mind this is a stock ECU which has never been tuned?? Is there anything I should be doing when I install a fresh AFM??? I have sine refitted the old broken AFM and the car is back to 'normal'.

The car will be tuned by Chip Torque on the 30th of May with a bigger Walbro Fuel pump and a new Unifilter and MRT Performance Cross Flow TMIC.

Any advice would be greatly appreciated, as I have to figure out if I need another AFM ASAP before the tune next week. BTW the AFM was bought new from a seller on eBAy who sells genuine OEM Subaru parts, it came new in the Fuji Heavy Industries/ Subaru / Denso box, so I am hoping it unlikely a failed AFM.

[kiahatsiu]

Most likely a dud AFM. Best bet would be find another person in you local area and try their AFM.
Or find out if the AFM on the 2.5 is the same part number, and PM DR20T and see if he still has one from the 2.5 tbSTi he is wrecking!

[-=HaZ=-]

Most likely a dud AFM. Best bet would be find another person in you local area and try their AFM.
Or find out if the AFM on the 2.5 is the same part number, and PM DR20T and see if he still has one from the 2.5 tbSTi he is wrecking!

The part number I have listed is the one I have on the original AFM, the OEM replacement one I bought is the same. Do these AFM specifications vary from model to model or are all AFM with that part number considered equal?

Can't believe the new AFM is a dud....seems to happen allot, well at least the users in this forum always seem to be complaining about failed AFM.

[cruisn]

Not so much failed afm that causes hunting as it is the oem o2 sensor just after the turbo in top of the dump in the twin scroll models.

Black smoke however will be afm as was the case with a dodgy afm in my Gen2 Legacy.

[-=HaZ=-]

Not so much failed afm that causes hunting as it is the oem o2 sensor just after the turbo in top of the dump in the twin scroll models.

Black smoke however will be afm as was the case with a dodgy afm in my Gen2 Legacy.

The O2 sensor was replaced when the turbo got rebuilt as the ECU was recording a CEL against the top most O2 sensor.

I contacted the seller/vendor of the AFM and he claims I MUST have the ECU reset, using the OBD II interface and associated software. As our car is a DENSO based ECU not JECS, the only way to do the ECU reset and clear memory using compatible software and a computer connected to the OBD II port (its non volatile, disconnecting the battery won't do it) and then connect the new AFM and allow the ECU to relearn.

This is a good source of info: http://www.scoobypedia.co.uk/index.php/ ... e/ECUReset

The car is booked in with John French tomorrow I will get them to install the new AFM and reset the ECU to see if that makes a difference.

[kiahatsiu]

Oh, so this is the silver TBsti sedan that was in there last week! I am interested to see how the vf34 upgrade works.
Ps, the guys at John French know their shit, I wouldn't worry too much.

[-=HaZ=-]

Oh, so this is the silver TBsti sedan that was in there last week! I am interested to see how the vf34 upgrade works.
Ps, the guys at John French know their shit, I wouldn't worry too much.

There was another Liberty GT owner(another forum) with the same model, car that had a VF38 re-cored to a VF34 ball bearing cartridge, stock exhaust, fuel pump, injectors, intercooler, the only mod apart from the V34 core was a hi-flow in panel filter, it recorded 175awKW at the same boost as the VF38.

I have had Brett Middleton from MRT Performance contact GCG Turbo(MRT do allot of work with them) and Brett claims yes the re-machined VF38 with the VF34 'will flow considerably more' (Bretts own words after speaking to the owner of GCG Turbo.)

I am having the fuel pump replaced with a Walbro, and also a uni-filter panel filter with a MRT Performance Cross Flow Intercooler. Whilst I still have the completely stock exhaust I have been told its not as big a restriction as the stock filter and intercooler, so for me it made sense to upgrade those right now and get it tuned.

I too am curious to see if the VF34 core will warrant an upgraded exhaust. I am hoping the dyno tuner at Chip Torque will be able to tell me if there is significant back pressure with the stock exhaust and if the higher flowing turbo core requires a better flowing exhaust.

I am talking to Trevor at Custom Exhaust Specialists at the moment and am considering custom extractors, front pipe and complete turbo back exhaust, however given the cost of work being carried out so far that will have to wait on the dyno results and will have to be done a later stage.

[kiahatsiu]

Any joy on this today?

[-=HaZ=-]

Any joy on this today?

No not yet. Although John French confirmed that a factory reset on the ECU is mandatory when changing ANY engine sensor, so the ECU relearns. The car is due to go in tomorrow to have the new AFM, Intercooler and panel filter installed, along with an engine oil change in preparation for the dyno tune Wednesday the 30th at Chip Torque.

[dr20t]

Enver

Where did you buy the afm from?

Mick

[-=HaZ=-]

Enver

Where did you buy the afm from?

Mick

$145 delivered.

http://www.ebay.com.au/itm/GENUINE-Impr ... 842wt_1111

Other new genuine Subaru parts from the vendor sold here.

http://stores.ebay.com.au/Auto-Sensors- ... 34.c0.m322

[-=HaZ=-]

Confirmed by John French Automotive.....dead AFM! Reset the ECU twice, the car just blew a heap of black smoke and wouldn't rev or accelerate past 40Km/h. Have to contact the vendor and return the AFM.

Car is back on the old AFM, and NOT experiencing the hunting problem.

[-=HaZ=-]

Got a replacement AFM coming from the vendor, should be here by Monday. Had the MRT Cross Flow intercooler fitted yesterday whilst the car was in the workshop. So far after the ECU reset the car is still learning, however the additional flow has made a very big difference in torque and the way the car drives. Upgrading the intercoolers on this model car is a must! Tuning should transform this car, look forward to the results.

[Ben]

Car is back on the old AFM, and NOT experiencing the hunting problem.

Resetting the ECU will usually fix it, but it will start hunting again. Contact PhatGT for one of the NEWER versions of the same part from Japan. Good price and should solve the hunting if it comes back in a few months.

[cruisn]

Car is back on the old AFM, and NOT experiencing the hunting problem.

Resetting the ECU will usually fix it, but it will start hunting again. Contact PhatGT for one of the NEWER versions of the same part from Japan. Good price and should solve the hunting if it comes back in a few months.

Afm, not o2.