Hello team. Still trying to fix issues with my 1993 BG5 (see here and here for earlier work done).
When the car is "cold" (first 5 or 10 minutes of driving), coming onto boost my AFR gauge will swing rich as would be expected.
At some point after driving 5 or 10 minutes the AFR response to boost gradually gets leaner. At first AFRs will swing to low 13s, then high 13s, then after more driving coming onto boost the AFRs will continue to read around the 14's!
If I hold and maintain boost the AFR will eventually swing rich again after several seconds, but never as rich as when the car is cold.
It's like something stops responding correctly, often as it warms up but not always. It only affects on-boost driving. Off-boost AFR continues to hover around 14.7
I'm fairly certain this issue is causing knock and sending the ECU into boost-limit mode, where I won't get more than 0.5 bar of boost.
I have had the intake tested (fixed a leak with no difference) and fuel pressure tested:
41.5 psi @ idle
50psi @ atmosphere
56.7psi @ 0.5bar
Possibly unrelated, but when starting the car from cold it will often (but not always) run lumpy for a few seconds, then come right. The mechanic has recommended an injector clean for this.
Any ideas of where to start with the lean issue or what to test would be greatly appreciated.
