[Oldschool]

Great diagnostic approach! Anxious to hear the results with the new Bosch units.

 

[Kory Nunn]

Update:

New Bosch FPR's work great.

I still had some idle issues, and I noticed LTFT bank 2 was always zero under all conditions, so I went down a rabbit hole thinking it could be related to bank 2 UEGO (lambda) never being "trusted" by the ecu, and therefore never being used to go closed-loop. I did a lot of digging and even found an official "how the UEGO works" PDF from Lamborghini, which describes what conditions need to be met for closed loop. One was the cat temps need to be correct, so I tested thermocouples, and they were fine. I then suspected thermocouple ECU, so I bought a new one and installed it, with no change.

Today I decided to just swap the ECUs from bank to bank, to see what would happen.

The stuck-zero LTFT followed the ecu to bank 1! The car now idles much more smoothly. I let it heat up and it didn't have any idle surging all the way to stable temperature. I went for a quick drive and it had no idle instability. After the drive I let the car idle in my garage for about 2 minutes, and there was some very faint change in RPM, but not the same as previously.

I'm going to monitor and see if things change, but for now my theory is the dead cats/gaskets through the car so out of spec that one of the ECU's is in some form of safe-mode. If this is the case, hopefully it eventually goes away on its own, or maybe I can get someone with LARA/TEXA to reset it?

Worst case scenario the ECU has issues and will need to be replaced.

Will eventually update here in the future.

 

[BrandSB]

Quick question, it looks like some oil drainage in your pic with the stock FPR, just curious if that came from the regulator? I have a similar idle hunting issue and my right intake manifold has an oil film inside, the left is spotless, trying to piece this together.

 

[Kory Nunn]

Quick question, it looks like some oil drainage in your pic with the stock FPR, just curious if that came from the regulator? I have a similar idle hunting issue and my right intake manifold has an oil film inside, the left is spotless, trying to piece this together.

It was just old dirty fuel. The left side has the low pressure pcv port right beside the fpr port, and the positive pressure pipe is right before the left hand throttle so it's not surprising that the left side gets dirty. Weird if your right side is oilier than left.

I strongly suggest getting and OBD2 scanner and watching short and long term fuel trims at idle (STFT and LTFT) for both banks, these can point you in the right direction.

 

[Kory Nunn]

Update:

After swapping ECU's between banks, I noticed that one ECU had a LTFT fixed at 0 at all times, and the other had a LTFT that moved all around the place.

I decided to buy a second hand ECU online with the same year/month of manufacture and very close serial code, and have it cloned from the old ECU.

Did this a few days ago and the car immediately drove better, however, I still have a surging idle when the car is hot.

The next thing I'm going to try is the sacer TPS upgrade.

 

[LpZero]

What is the sacer TPS update?

 

[Kory Nunn]

Replacing the OEM resistance strip based throttle position sensors with hall effect sensors. Lots of Volvos use the same throttles and they often get idle issues that can be caused by the standard tps's.

 

[ablettdc]

I’m looking for 2 cheap Sacer SA300 Throttle Position Sensors but with recent trade tariffs what used to $100 sensors have become $175 each plus shipping. Let me know if you are able to source them at a reasonable price.

 

[Kory Nunn]

No idea on US sorry, but I just grabbed a second one last night for $100AUD ($65USD).

Put the first one in this morning and it works good. will make a dedicated how-to thread once I get the second one and can compile some photos.

One big help was that I'd already opened the throttles up and cleaned the contacts, and because I expected I'd eventually do the sacer fix, I didn't glue the covers back on, and instead printed retainer clips:

Have to say I was putting it off because I thought it was going to be a bit difficult but tbh it was pretty easy.

Idle not yet verified, and not really going to judge it till I get both throttles done.

 

[Kory Nunn]

Final update: It's solved!

I did 2 more things to sort the idle:
I added a restrictor to the purge valve inlet, to reduce the amount of purge vapours that the car can ingest. The purge still operates, but it no longer has as big an impact on idle as it did before. I'm considering removing this restrictor and just re-doing the second thing to see if it was necessary.

The workshop manual mentions a procedure to automatically learn/adjust DBW for idle. The process is to turn the car on and idle until you can get the water and oil to 90C, and at that point it will learn the idle. The issue I've always had is that my car never get's to 90c because both fans come on before it can get there. I ended up pulling both radiator fan solenoids to get it to 90, then I put one back in and drove around under various conditions to get it to learn. This seems to have almost completely removed my idling issues, and the car now has only the faintest oscillation in RPM at idle.

All in all, my idle instability was caused by multiple things:
Dead VVT solenoids, dead cat gaskets, bad TPS's, and it's inability to get to self-learn temp.

I've updated the first post to fully log everything done and what worked.

 

[Bully69]

Final update: It's solved!

I did 2 more things to sort the idle:
I added a restrictor to the purge valve inlet, to reduce the amount of purge vapours that the car can ingest. The purge still operates, but it no longer has as big an impact on idle as it did before. I'm considering removing this restrictor and just re-doing the second thing to see if it was necessary.

The workshop manual mentions a procedure to automatically learn/adjust DBW for idle. The process is to turn the car on and idle until you can get the water and oil to 90C, and at that point it will learn the idle. The issue I've always had is that my car never get's to 90c because both fans come on before it can get there. I ended up pulling both radiator fan solenoids to get it to 90, then I put one back in and drove around under various conditions to get it to learn. This seems to have almost completely removed my idling issues, and the car now has only the faintest oscillation in RPM at idle.

All in all, my idle instability was caused by multiple things:
Dead VVT solenoids, dead cat gaskets, bad TPS's, and it's inability to get to self-learn temp.

I've updated the first post to fully log everything done and what worked.

Legend mate!! Well done