Readings on AEM UEGO display vs. MSnS signal don't agree, ideas?

[Slow_Old_Car]

I'm sitting out here in my driveway right now w/ my car idling, the AEM UEGO wideband gauge on my steering column says between 12.6-13.0 idle AFR like usual.

 

The air:fuel ratio readout in MSnS reads 15.4-16.2ish.

 

I've checked the settings.ini file and the UEGO 0-5v setup is turned on according to it. So i don't see why the readings are getting skewwed.

 

Car is idling at 160 degrees right on the thermostat and has been for about 20 mins, so i am fairly certain the readings coming from the MSnS gauge side are innacurate cause i'd be heating up pretty good at that lean of an AFR.

 

Any suggestions? The only thing i can think of that i've changed in recent times was i went from this laptop i'm on having one single megasquirt n' spark profile, to having 3 different cars profiles on here. But even then i created new files for each car, which then assigned there own files in the MSnS directory, of which each one has a seperate settings.ini file.

 

I'm trying to rough out a tune for the track this weekend, so i gotta figure this beast out pretty soon.

[Slow_Old_Car]

This is really wierd...

 

Busted out the calibration sheet that AEM has on there instructions...

 

Fixed points:

Car is sitting still at idle turning 850rpms, making 13.8v at idle.

 

Situation 1:

Car on and idling, with a multimeter hooked up at the join point between the output wire of the UEGO (white wire), and the 02 input wire of the MSnS harness (pink wire).

 

UEGO displays 13.0:1 AFR

MegaTune displays 11.6-11.8:1 AFR

Multimeter shows 1.00-1.07v which equates to 12.00-12.25 AFR

 

Situation 2:

Car on and idling, with no multimeter hooked up at the join point between the output wire of the UEGO (white wire), and the 02 input wire of the MSnS harness (pink wire).

 

UEGO displays 13.0:1 AFR

MegaTune displays 14.5-14.7:1 AFR

Multimeter is not hooked up and therefor displays nothing

 

Situation 3:

Car on and idling, with multimeter hooked up at the end point of the output wire of the UEGO (white wire), with the 02 input wire of the MSnS harness (pink wire) having been disconnected.

 

UEGO displays 13.0:1 AFR

MegaTune displays 9.72:1 AFR as it is recieving no signal obviously

Multimeter shows .99-1.09v which equates to 12.00-12.25 AFR

[Slow_Old_Car]

I've gone through and cleaned every contact splice pertaining to the wideband and it's controller. I also have taken the wideband display off the steering column and in doing so and checking it's connections found brown discoloration on the plug that goes into the back of the display on the ground wires terminal.

 

Since the unit is still operational it makes me think the grounding path is good, but this could have damaged somthing on the circutry inside possibly i suppose.But without a circut schimatic i wouldn't be able to figure anything definative out for sure that i can think of.

 

Anyone have any ideas that i might have missed in trouble shooting this?

[Slow_Old_Car]

I'm leaning towards bad UEGO controller at this point since i had this laptop, this megatune install, this connection cable, all plugged into the other Z i was datalogging for the aluminum vs. mild steel thread, which that car had a Innovative LC-1, its own seperate profile w/ LC-1 setting.ini, and then an identical MSnS v2.2 setup.

[mobythevan]

Could it be the same issue that some of the LC-1 widebands had where you are required to have a series resistor in line to the megasquirt? Without the resistor the connection to the megasquirt would draw too much current and cause ??? (can't remember what happened, just remember you needed the resistor)

[Slow_Old_Car]

Could it be the same issue that some of the LC-1 widebands had where you are required to have a series resistor in line to the megasquirt? Without the resistor the connection to the megasquirt would draw too much current and cause ??? (can't remember what happened, just remember you needed the resistor)

 

Not sure, the AEM forums regarding this is just about complete rubbish. This UEGO system has been working in my car for 2 years or so now, so i'm more inclined to go with absolute failure.

 

I just can't figure out why having the voltmeter clamped onto the join point of the white and pink wires causes the readings on the laptop to change a full 2-3 points leaner. The voltmeter has it's own batteries built in so it's not sapping power, just doesn't make sense.

 

Unfortunately i'm also the only UEGO user around here that i know, so simple swapping the gauge brain to determine if it has gone bad isn't an option.