May I suggest that you cross check the water temp sensor resistance readings @ the ECU end of the temp sensors wire connections at the ECU?
Trace & disconnect the temp sensor wire connections at the ECU in order to test that the temp sensors resistance at the end of the wires is almost identical to that of the sensor?
Give the values found?
Resistance in the wire/terminal lugs/connectors may produce a signficant misreading at the ECU at 20 c @ 2.5 Ohm K or less starting temperatures?
Quote
; “ I am waiting for the new sensor to arrive, so removed the old sensor and tested it against these figures I found on this forum:
The ecu coolant sensor should read-
0.25 ohm @ 90c
0.85 ohm @50c
2.5 ohm @20c
My sensor gives:
0.3 k ohms @ 85 c
2.4 k ohms @ 24 c”
Happy fault finding
Hi,
I have come back to this problem now I have more time.
Meantime, I have been using the 'fuel on filter' workaround just to cold start in the mornings and its been fine.
I have noticed in the live data on my OBD2 reader has the following:
IAT(°C) 29 (Inlet Air Temp)
ECT(°C) 27 (Engine Coolant Temp)
These values are entirely consistant for a cold engine, with the outside air temperature of 28° at the time. Also these values increase as the engine warms up during running.
From this I assume the temperature sensers are working and the wiring is good.
On another tack, another thing that changes fuel is Fuel Trims. Frank aludes to this...
that short term fuel trim does,nt look right mark
need a copy nissan consult really
Looking more closely at the Short Term and Long Term fuel trims...
SHRTFT1(%) 1.6 (Short term trim goes up and down under 5 at idle. Ramps up when I rev the engine. Seems normal from what I understand)
When I disconnect the o2 sensor (before the cat) short trim goes to 0 as you would expect.
O2S11(V) 0.1 (I assume this is o2 sensor (1) and goes up and down between 0.1 and 0.8. This is what controls the Short term trim).
LONGFT(%) -0.8 (long term trim is average calculated from short term I understand)
It's these other trim values I dont get....
SHRTFT11(%) 0.8 (Looks same as SHRTFT1(%) but its on another screen so cant see them together. goes up and down in similar range.)
O2S12(V) 0.3 (I assume this is o2 sensor (2) and is static around at 0.3 even with cold engine. This is the lambda sensor after the cat I think.)
SHRTFT12(%) 99.2 (This never changes, even with cold engine and both o2 sensors disconnected)
Writing this down, logically it looks like o2 sensor 2 might be controlling this other Short term trim, but is not working.
From what I have read, this shouldn't prevent the engine from starting cold, should it?
Any thoughts or ideas greatfully received.
Mark
www.almeraownersclub.com
