Reason for finally posting is that I have an issue I just cannot figure out and I need all of your expertise to fix it!
So. What are we working with here?
2002 V40 T4 with some mods.
- The engine has H-profile rods in it for safety. Otherwise stock.
- 18T Kinugawa turbo.
- Bigger intercooler and a catless 3″ exhaust.
- 340 LPH AEM fuel pump and stock injectors. Fuel pressure is still at 3 bar over vacuum.
- LPG installation
- Boost Gauge
- AEM Wideband Gauge
- Remapped ECU (and an original ECU as a backup/reference)
What fault codes do I have?
- Camshaft postion solenoid (it’s persistent because the LPG computer hijacks the signal, car ran fine with this code prior)
- Lean running
What is the issue?
The car starts fine. After a few seconds it starts to misfire and struggles to stay running. I’m guessing this is the moment it starts to run closed-loop. This lasts for about 10 seconds and AFR is going wild at this time. After the misfires clear up it runs between 15:1 and 22:1 AFR, whatever it feels like that day, until the engine has some temperature in it. Under load it tends to reach the target value of 14,6:1, especially over 2000rpm. Every time I lift and hit the gas again (manual gearbox) it runs lean for a few seconds and then slowly creeps back to 14,6 over a few seconds. When I rapidly tap the throttle in neutral it runs at 25:1 or worse.
It doesn’t run any richer when I disconnect the vacuum hose to the fuel pressure regulator when idling. This causes the fuel pressure to rise from 2,2 bar to 3 bar, so it should start to run richer. But it doesn’t. I of course block off the vacuum leak to the intake manifold when doing this.
As soon as i switch over to LPG the engine stumbles a bit and the AFR goes to 8:1-ish until the ECU catches up and trims back to 14,6. While running on LPG I don’t really have any lean running at all. Fuel trims are also neutral. This causes me to suspect the petrol side of the fuel system.
While idling cold the MAF reads 20kg/h of air. This should be about 8-10kg/h. So the Injector duty cycle is trimmed to the max. But both the ECU and my standalone wideband read very lean values and the engine doesn’t run nicely.
What have I done to fix?
- Checked for vacuum leaks. None
- Checked for leaks around exhaust manifold, turbo, downpipe. None.
- Compression and leakdown test. Perfect values (engine is fully rebuilt only 40k ago)
- Swapped stock ECU back. No change.
- Unplugged MAF. Runs even worse.
- Unplugged Lambda. No change
- Unplugged MAF and Lambda. Runs even worse.
- Retimed the engine just to be sure
- Redid the wiring loom from scratch, as it was kinda dodgy anyways.
- Bypassed the LPG system (it intercepts the fuel injector signal)
- full out parts cannon. Replaced ALL electronics related to engine management. MAF, MAP, Lambda, Temp, Crank sensor, Cam sensor, etc. Everything is fresh, all values report back normal.
So my question now is; what the hell?