Running too lean
Discussion
We have a Caterham with well tuned 2 liter Zetec(280 BHP at the flywheel) . It has just decided to run really lean, banging ,farting a the occasional flame. Checked it and found badly cracked exhaust and assumed this was the problem. That's now fixed but still the same .
What does the panel think, any opinions gratefully received
What does the panel think, any opinions gratefully received
I don't know anything about this specific engine, but since there isn't many answers yet, I'll throw in what I know about the average complicated modern engine. :-)
A damaged oxygen sensor may mess up the fuel ratio for parts of a map and throttle positions that rely on the O2 sensor to adjust the mix.
If you had a big air leak into the exhaust, it may have damaged the sensor.... or your computer may have "learned" an erroneous area of settings due to the leak. Depends on your ECU and all that. A subaru can "learn" to adjust areas of a fuel map by 8% or more, to match feedback from the O2 sensor, for example. When we are tuning a modified Subie, we are happy if the learning stays within 5% of perfect.
I don't know what your engine does in those respects; if it learns or is more primitive. :-)
A mis-aligned throttle sensor can cause the wrongs part of a map to be used as well, but maybe not with such dramatic results.
You could also have a blocked fuel injector, or injector wire damage - if it seems to be running rougher.
A fuel regulator with a bad diaphragm may cause a drop in fuel pressure which will make you run lean...
Bad timing can produce some interesting noises, too.
A MAF sensor scaling going odd from a bad sensor will do wonderful things to fueling, as well.
If you can hook a laptop. or even an OBD II reader into your ECU, that's the place to start. to look for error codes and obviously odd sensor readings.
I once had intermittent shorts in my main O2 sensor harness, and it made the car lurch and surge and pop at low cruising speeds, with AFRs going all over the place. Took ages to track down.
A damaged oxygen sensor may mess up the fuel ratio for parts of a map and throttle positions that rely on the O2 sensor to adjust the mix.
If you had a big air leak into the exhaust, it may have damaged the sensor.... or your computer may have "learned" an erroneous area of settings due to the leak. Depends on your ECU and all that. A subaru can "learn" to adjust areas of a fuel map by 8% or more, to match feedback from the O2 sensor, for example. When we are tuning a modified Subie, we are happy if the learning stays within 5% of perfect.
I don't know what your engine does in those respects; if it learns or is more primitive. :-)
A mis-aligned throttle sensor can cause the wrongs part of a map to be used as well, but maybe not with such dramatic results.
You could also have a blocked fuel injector, or injector wire damage - if it seems to be running rougher.
A fuel regulator with a bad diaphragm may cause a drop in fuel pressure which will make you run lean...
Bad timing can produce some interesting noises, too.
A MAF sensor scaling going odd from a bad sensor will do wonderful things to fueling, as well.
If you can hook a laptop. or even an OBD II reader into your ECU, that's the place to start. to look for error codes and obviously odd sensor readings.
I once had intermittent shorts in my main O2 sensor harness, and it made the car lurch and surge and pop at low cruising speeds, with AFRs going all over the place. Took ages to track down.
Gassing Station | Caterham | Top of Page | What's New | My Stuff