Chris77 Posted December 31, 2022 Report Share Posted December 31, 2022 Hello This is what happens when amateurs mess with things Short version , afr guage goes lean a few minutes after start , second afr system does the same but comes back at mild rpm/mild load . I've wired an atom g4x into a off road vehicle running a rover v8 . The carb intake has been replaced with a later model injection intake with factory injectors , custom trigger wheel in the dizzy and wasted spark coils . AEM o2 guage via analogue input . Much to my surprise the stupid thing fired up as I was trying to test the trigger pickup , go figure . Injector dead times are unknown , if anyone knows what 94 rangerover injector figures are or where to find them I appreciate a head up . Anyway thats about as far as I got as a couple of minutes after start the afr started going lean . My first thought was the cold start was ramping off too fast so I started to chase it with master fuel (this was the first start etc ). It quickly became clear this was a false reading as the engine bogged and belched smoke . Tuning it to max vacuum at idle put me back to the original master fuel . The afr guage dashed out , however the engine seems to be idling just fine , smooth with no misses etc . Wondered if I have just cooked the sensor . Day two and I swapped on my o2 sensor system from a working setup and it did the same thing , interesting . However lightly driving the thing and the sensor comes back after about 10 to 15 seconds or so , after returning to idle it eventually rolls lean again . During this time the fueling does not appear to change significantly , the motor sounds and runs smooth . So at this stage I think its guage wiring or placement issue . Hence the suspected heat/location issue . As above , amateur , so bugger all experience with failed o2 setups . First guess is its lack or heat , key on heats the probe so life is good , however the probe is too far down the exhaust so cools off and shows lean . Drive it a little and the sensor sees more hot gas and warms up thus reads again. The sensor is in the end of the 4-2-1 collector , about the base of the firewall , so further than I would like but not miles away ( I thought ) . Second guess , well dont really have one . Maybe an air leak up stream , but why is it good for the first couple of minutes and why does it come right being driven . I have had a quick google and one post has the same fault but does not give any solution , another from this forum says after replacing the faulty o2 sensor he found the master fuel was way to high . I do not believe the sensor is faulty as two systems show similar results , different o2 sensors and wideband controllers . So what are the common o2 sensor issues ? I'll google some more but do the controllers heat the sensor constantly or only at power up , this will debunk my heat theory straight off . How far is too far down the pipe ? If the sensor is not in the pipe enough can this cause issues , I would have though it would have to be way wrong to give this sort of an issue . The sensor is located at horizontally so not collecting moisture etc . Sorry for the novel but interested in any responses , cant progress with this until this issue is resolved . Need some confidence in the afr reading . Oh and if it matters (as it was mentioned in the thread with similar issue) master fuel is currently 17 and the fuel table is about 48 (too high to me) . Change of master fuel from 16 to 17 moves the afr (when it seems to be reading ok) from 13.5 to high 14's . Bigger jump than I expected , but if it was working I'd run the higher master fuel and bring the table down . Cheers Chris Quote Link to comment Share on other sites More sharing options...
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