vn commodore with engine management issue.

[mag]

As title suggests, have vn commodore running 12p 808 ecu that develops a miss-fire from inappropriate fuelinghen coolant temp rises in slow traffic. Logging shows normal CTS temp and MAT operating range. If the cts is disconnected the engine returns to smooth running no misfire. CTS has been replaced and ecu wiring including ground connections have been checked. The problem was not solved however if my understanding of the 12p software is correct, with the CTS disconnected a default coolant temp max of 93 degrees is substitued. This suggests that coolant temperature approaching 100 degrees are an issue at low to . Which 12p tables would be most effective in changing the fueling in this are.

[delcowizzid]

When you unplug the sensor the fan should come on after a delay time of a number of seconds. 808 ecus had issues with the tracks for the coolant sensor circuit the conformal coating would shrink and bubble up and pull the traces.when it starts failing coolant temp readings would go all over the show at random .idle would go bad black smoke out exhaust every now and then.and nek minute be fine again

[vlad01]

In 12P there is the inverse temp term table where after 90 something deg the corresponding charge temp I think would be set at -23c, so as the engine heat soaked after a hot shutdown, this was meant to band aid a hot restart lean out. This might have something to do with it.

Since I worked out these engine benefit from an 82 deg thermostat, pretty much all these factory issues go away on my cars, the cars run slightly more efficiently too I found and also have a more stable coolant temp when in cold weather since the engine and thermostat aren't constantly fighting to keep the coolant closed off and trying to keep warm.


Another benefit I found is higher knock ceiling and slightly more power (or rather not as a big power loss when heat soaked or at full temp).


I have had far less idle issues by avoiding the heat soaked condition and it's workarounds in the tune by just the thermostat change.

[mag]

Have done more test runs after adjusting the charge temp upper range, -20 degrees at 104 temp appears savage when std thermostat only just fully open at 102 and fan supposed to cut in at 100. Still have the stumble at low revs and throttle application when coolant temp above 90 degrees in slow traffic. Will fit an 82 deg thermostat and try again. Have also tried to lower fan cut in temp but do not apper to be able to alter bin. Is this possible with the $12p program. Would may more sense to match with colder thermostat.

[immortality]

Something not right there, stock thermostat is 195°F or ~91°C.

But I agree with Vlad, a cooler thermostat is better.

You can definitely alter the themofan on temp in 12p

[mag]

Could someone provide instructions for altering fan cut-in temp in $12p. Have swaped to ecu with oem ATFY bin and issue persists. Disconnecting CTS also fixes problem when using ATFY bin.

[mag]

Also could someone identify the test point in the ecu that $12p uses to measure battery voltage for monitoring puposes. Thanks

[mag]

Looks like all previous comments regarding CTS disconnect curing the problem maybe a furffy. More testing suggests the ignition cycling, whene disconnecting the CTS, resets something. Engine restarts and run smooth although startup idle is 1500-1700 rpm before settling to 700 which also happens when CTS is disconnected. Any help would be appreciated.

[mag]

Issue continues although every sensor with the exception of the MAP has been changed. Most resent test ride has raised the suspicion that the problen is baro related. The test drive loop begins at 675m above sea level and ends at 32m above sea level. The engine stopped and restarted at 32m above sea level, shopping complete, and the issue occurs on the return run back to 650m above sea level. Have a new MAP sensor to fit. If it is the fix then what would be the explanation and how does disconnecting the CTS correct the problem.

[Charlescrown]

The best thing is to post a log. My gut feeling is it's all in the tune but a log will show a lot of info.