Strange Flex Fuel Sensor Reading at WOT

[LordLo]

Hi guys,

I just installed a GM flex fuel sensor and it is reading fairly accurate when in low to medium throttle.

The issue I have is at WOT the sensor readings go out of wack/glitchy and Sensor Failure kicks in, bumping correction up to 150%!

Anyone happen to know what the issue is and how I can fix it? Thank you.

[turbo355]

Im seeing some what the same , mine dosent do it all the time but its pretty regular .

[LordLo]

It suxs for me since I'm running 1000cc injectors and a 50% jump is huge.

[elutionsdesign]

Where do you both have the sensor plumbed? Can it be seeing big pressure swings at that point?

[turbo355]

In the return line on mine ,shouldnt be any pressure there.

[jsmcortina]

I believe I've looked at this on the bench before and nothing jumped out. I'd like to send some debug code to you both that will record the input data into sensors14,15 (and similar) so I can see why the fault is being tripped.

James

[LordLo]

Ok send it over.

*my sensor is on the return line.

[LordLo]

Just for the hell of it, I decided to redo my wiring. Originally I had the GM Flex Sensor ground shared with the other sensors (CLT and MAT), but today I decided to just mount the ground onto the chassis for testing purposes. I also ran a separate wire for the 12v+; before I spliced into the ECU 12v+. Finally, I redid the GM Flex Sensor connector.

I just took my MR2 for a 30 minute drive and did 4-5 WOT tests and there is no more sensor failure/odd surge spikes. It *appears* the issue was probably in my wiring.

Hopefully the problem doesn't reappear in the future.... but for now ->

[LordLo]

Probably spoke too soon. The problem still exist, but just at much lower frequencies.

Maybe write in a code to limit sampling time on the Flex input? Much like how the TPS has the Lag Factor setting.... perhaps the Flex Input needs one too.

[S.Bretz]

I had issues years ago when I had my 5v ref coming off the old OEM ecu and the ground to the FF sensor was off away from the MS ground...when I stabbed the throttle some times I would see spikes that would induce a correction factor as large as 400%...with 1000cc injectors that was a lot.

It ended up the wiring created noise...installed the wiring per the manual (and installed a protective circuit per James) and it all went away.

[elutionsdesign]

I just noticed my ethanol percentage is pretty spikey, as well as the fuel temp. Fuel temp was 92 F but spiking down to -40. Would be nice to have some smoothing there.