Syvecs Forums

One more element to my misterious variation.
Today I drove for around 1h30. I had 2 VVT fails at the begining and when engine was hot for around 30 min, both AVCS signals came back suddenly at the same level and were very "clean". No more fluctuation during 1h, all was really perfect..... I'll swap AVCS sensor between Left and Right to see if the defect follow the sensor.

I tried to check the famous banjo screen filter and decided to remove the banjo bolts that feed the avcs on the left side, where I have the problem.
In the same time, I washed the AVCS rigid oil feed line.

Guess what I found in the screen filter : an aluminium chip !! (bottom right on the picture) it seems to come from machining operation rather than a failure somewhere.



Of course I removed it and decided to not re assemble the screen filter.

Had it changed something now ? Not completely but there was an Impact on my problem that's sure. Anyway I still have VVT fails when cold and if I drive it fast, then nothing. Only when cold and during light cruising.... driving me crazy this...

Now, problem is Fixed !!!



Both signals are ok and no more VVT Fail !!

After lots of though and log analysis, I came to the conclusion that the ECU had many difficulties to control the AVCS solenoids, just like if they didn"t want to cooperate, not all the time, but sometime. This was not a true failure like a cutted wire, which is easier to track and fix.

I've re open all the engine loom that control the solenoid, checked all weldings and found that at some point a wire was damaged with 2 or 3 copper wires cutted, out of the wire insulator and still very close between them, so I repaired it and now all is fine, logs are now perfect since few days, signal are good on both AVCS pulley and no more VVT Fail since few days !!

I suspect that the cutted copper wire were sometime in contact and sometime not in contact, depending on vibration and/or ambiant temperature and this cause some interferences that the ECU was trying to compensate. Doing this, I think, it increased the problem until it was out of control and a VVT fail appear then. Just like the natural frequency vibration of a bridge that end by the complete destruction.

Now both signals of VVT 1 and VVT2 + Oil pressure are solid and no more uncontrolled fluctuation

Hope it could help someone

Nice result, wiring issues can be difficult to find.

Although I guess with hind sight, if you had scoped the wires at the solenoid itself, this may have shown an issue.

but that is easy to say now...and assuming a scope is available.

Those are the absolute WORST faults to track down.

Slowie wrote: ↑Fri Sep 25, 2020 11:15 am Those are the absolute WORST faults to track down.

Although one aspect with the OEM ecu...I believe it also monitors current draw from the solenoids, which might have highlighted something if logged.
Aftermarket ecu's wouldnt offer the same info.

That makes race cars with PDM/PDUs a pleasure to troubleshoot, in comparison to a road car.

Slowie wrote: ↑Fri Sep 25, 2020 6:32 pm That makes race cars with PDM/PDUs a pleasure to troubleshoot, in comparison to a road car.

Although in this instance it would be very unlikely to use a dedicated 12v output from a PDM to only 1 VVT solenoid in order to monitor current like the OEM ecu does.

One thing I learn is to not weld connections between wires under the bonnet, but to crimp it with the proper tool.
I tried to properly weld some wires of AVCS solenoid, but after few days it started again to fluctuate. Same defect was back with no wires damaged.

After checking the OEM spare vehicle harness I've seen that all the wires were crimped under the hood when they need to connect 2 wires.
So I decided to remove the welds and crimp with proper tool and now troubles had gone.

If it come back, I'll make a separate harness dedicated to AVCS solenoid.

It's not that easy with the flyback diode on the harness.

Chartreux wrote: ↑Sun Oct 11, 2020 5:39 pmIt's not that easy with the flyback diode on the harness.

Wire the diode in back at the ecu - much easier and, anyway, where it ought to be. Or buy a ready made conversion loom