Megasquirt AFR gauge swinging wildly

[rbfury]

Megasquirt AFR gauge swinging wildly

Hi All

I just got my Zetec SE 1.6 running on Megasquirt 2 with Techedge 2J2 wideband O2 sensor. I have it ticking over nicely by adjusting the fuel and spark to achieve the lowest MAP. The problem I have is that the AFR gauge on the Tunerstudio screen swings wildly from about 11 to 15 about 3-4 time a second.

- I have double checked the set up in Megasquirt and tunerstudio that they are set up for a Techedge 0-5 volts
- I have monitored the Techedge with the laptop through their software, the output is a stable 12.8 AFR
- I have checked the techedge 0-5 volts with a multi meter, it is stable (+/- 0.15 volts)

The only time Tunerstudio AFR meter is stable and reading correctly is when I disconnect the crank sensor!!!!

- I have checked and remade all the earthing
- I can take the O2 sensor out of the exhaust and leave in free air, disconnect the coilpack and the injectors, remove all the fuses I can. Then turn over on the starter and it still swings as before.

Any ideas would be much appreciated

I shall post the .msq when I find out how

rbfury

[trakkies]

How have you grounded the 2J2 output?

[rbfury]

The WBlin- is groundedto the engine block along with its heater and the MS grounds, TPS and temp sensors.

[LT401Vette]

- I have double checked the set up in Megasquirt and tunerstudio that they are set up for a Techedge 0-5 volts

Did this include calibrating the AFR table under:
Tools --> Calibrate AFR...

[trakkies]

The WBlin- is groundedto the engine block along with its heater and the MS grounds, TPS and temp sensors.

WBlin- (ground link removed) should go to the MS sensor ground along with all the other sensor grounds. MS should then be grounded to the engine block. The TE power ground should go to the block ground.

[rbfury]

I have calibrated the AFR table and all the grounds are as described by Dave. The ground link is removed from Wlin-

[LT401Vette]

Are you having any other odd side effects or getting any ini mismatch errors?

[rbfury]

That's the thing, there seems to be nothing else wrong. When on tick over every trace on a data log seems to be pretty stable except for the AFR - puzzling!

[LT401Vette]

Hmm... I guess...

I have checked the techedge 0-5 volts with a multi meter, it is stable (+/- 0.15 volts)

No wild swings there, but what kind of multi-meter is it. Some of the digital ones do a lot of averaging, so you won't see swings much. Where an analog will usually show a moving needle better.
Does it display a voltage that you would expect for the AFR the gauge is reading?

Separating it out...
- If the gauge in TS and Datalog value match the expected value for the voltage measured on the pin, then the issue is on the WB controller side.

- If the gauge and data log don't match the voltage, there is either something set up wrong or wired wrong to the MS.

Do you have a stimulator to apply a known steady voltage to the MS. That could help narrow the above to external wiring or config/internal wiring.

[rbfury]

Thanks for this Phil. I am away from the car until Sunday evening. I will try and confirm all you have suggested then.

I don't have a stimulator as I bought MS ready built, is there an easy way of supplying a steady voltage between 0 - 5 as a trial?

[rbfury]

What would happen if I connected the + of a 1.5v battery to the lambda wire to the MS? Would help indicate if the problem was techedge or MS?

[LT401Vette]

What would happen if I connected the + of a 1.5v battery to the lambda wire to the MS? Would help indicate if the problem was techedge or MS?

The TS gauge should read about 12.0:1 and hold steady

[rbfury]

Right, I shall try the 1.5v while it is idling to see if TS is stable. Won't be until Monday though.

Thanks again

[rbfury]

Thanks for your thoughts, it seems to be an ecu fault so I have sent it back to the builders to check and rectify. I should get it back in a few days and will post report

[rbfury]

I sent the ECU back to Phil at ExtraEFI who found a bad solder connection, all sorted and returned within 4 days - thanks Phil