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ECU Thinks it's Rich when it's actually lean
- SailorBob
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7 years 10 months ago - 7 years 10 months ago #21659
by SailorBob
ECU Thinks it's Rich when it's actually lean was created by SailorBob
1999 Nissan Almera ( Euro Sentra ) 1.6L GA16DE ( NOT OBDII compliant )
Complaint: Car was misfiring, then no-start, and in general runs lean all the time at idle
Heated Front O2, Distributor and Injectors have been replaced ( all necessary - this fixed the first two problems )
After replacing the dizzy and starting the vehicle I noticed that the O2 was switching for a bit then stopped switching. The thing that threw me for a loop was that the ECU was pegged reading Rich, and was subtracting fuel -5%, yet the O2 was pegged lean.
Once the engine gets above about 1k rpms, the O2 switches normally. There are no air leaks I can find, and the MAF waveform looks OK on the scope.
You can see what I'm talking about here:
The green line is A/F Base, which is the only fuel trim PID I have available, and it's reading 95, which means -5%.
The pink line is what the ECU thinks, rich or lean, and the blueish line overlayed with the pink line is the O2 signal.
Complaint: Car was misfiring, then no-start, and in general runs lean all the time at idle
Heated Front O2, Distributor and Injectors have been replaced ( all necessary - this fixed the first two problems )
After replacing the dizzy and starting the vehicle I noticed that the O2 was switching for a bit then stopped switching. The thing that threw me for a loop was that the ECU was pegged reading Rich, and was subtracting fuel -5%, yet the O2 was pegged lean.
Once the engine gets above about 1k rpms, the O2 switches normally. There are no air leaks I can find, and the MAF waveform looks OK on the scope.
You can see what I'm talking about here:
The green line is A/F Base, which is the only fuel trim PID I have available, and it's reading 95, which means -5%.
The pink line is what the ECU thinks, rich or lean, and the blueish line overlayed with the pink line is the O2 signal.
Last edit: 7 years 10 months ago by SailorBob.
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