aggravation

I'll send it to you but the files I'm using are the ones Tim provided, they are copies of the files he burns on the chips he sent with the kit. I use the files because I have the PEM's installed in my LH and EZK....

I definitely appreciate anything you guys can do!

AO

Well if it's Tim's chip, then it probably isn't the chip - I've been in his car, and it doesn't do this. The only thing I can think of is the MAF, an intermittent air leak (unlikely), or fluctuating fuel pressure (perhaps a flaky fuel pump or relay?)

You say the lean condition is sporadic, but is it repeatable?

You say it never happens under WOT, but remember you're only under WOT for a few seconds at a time.

AO

Got the bin file... I loaded it into my handy dandy LH Fuel Map Tweaker and everythign looks pretty happy. I was wondering if there were any cells that may be maxed out, there aren't any.

So it's not the chip.

thinking...

aggravation

When I said it doesn't happen under WOT throttle I should have said it doesn't happen under acceleration. As far as I know it doesn't happen under WOT either but I've hardly been WOT since this started...

Once in a while I feel a slight stumble or something under acceleration but it doesn't happen nearly as often as the sharp swing to lean AF ratio when cruising does and when I feel that stumble I don't see the AF gauge swing up to lean territory although maybe it's just quicker then. When it "goes lean" at cruise it seems to be a cycle of on and off and I have to accelerate or downshift to get it to stop.

John Speake

Are you feeding NBO2 from your LC-1 back into your LH ECU ? Ot susing a seperate NB sensor ?

Some issues of LC-1 software have been known to caused rapidly changing reported A/F figures and outputs.

You could just try disconnecting the O2 sensor (ground the O2 signal input wire into the LH) which will force the LH into a default mid range setting of the loop. Then test drive again.

AO

You're running the stock fuel pressure regulator, right?

aggravation

I'm not currently feeding the analog narrow band simulation from the LC-1 to the LH ECU. I have a new narrow band Bosch O2 sensor for the cars computer to use.
I have temporarily tried the LC-1's output to replace the previous narrow band O2 sensor and at that time there didn't seem to be any difference. So I'll go disconnect the new narrow band O2 sensor and see what happens.

Question: Because I had been trying the LC-1's output connected to the lead that feeds the O2 signal to the LH I have a reusable butt connector on that wire. so can I just disconnect that wire to achieve the same result or does it need to be grounded?
Also, does having that connector in the lead have a potential for any problems like the symptoms I've got?
Likewise, when replacing the narrow band O2 sensor last time, the lead on the Bosch unit I bought was quite short so there is a permanent splice using a crimp butt connector under the car about ten inches from the O2 sensor then the reusable butt connector inside the CE area...

aggravation

Yes, I forgot to add that to the list of parts I've changed out.
Right now I have a brand new stock fuel pressure regulator. It seems to give around 55psi under vacuum.

MaineShark

There is no such thing as running lean during cruise. Don't worry about it.

It's closed loop, the computer is taking care of everything. Make sure your o2 sensor is good and your computer is good.

MaineShark

Yeah, that's normal behavior for a car in closed loop. Don't worry about it. Every car in the world that runs off a o2 sensor during cruise does this.

No worries.

aggravation

It isn't normal...either that or my car just now started running "normal" after having been running really well previously!
The rapid and dramatic swing to "lean" as I describe it causes the car to run like someone is intermittently tapping the brakes or cutting off the fuel supply and this coincides with the swing in the AF ratio readout. For all I know the actual AF ratio is normal but something electrical is flicking on and off causing the AF gauge to blip....

John Speake

Hi Craig
As long as you haven't got long floating wires and good solid crimp joints, then you shouldn't have a problem on that score.

Some versions of LH ECU software recognise a disconnected O2 sensor better than others. A battery disconnect after unplugging the sensor is a 100% method I have used, without needing a ground.

All non-cat cars do have the grounding link as stock.

Your cars symptoms are unusual.......

AO

It's not the bin file, it's not the O2 sensor, and it's not the gauge.

Fuel pump? Maybe...

I would try swapping the fuel pump relay just for giggles.

Also, can you try logging with the cruise control enabled. It will highlight if anything weird is happening.

Tim Murphy

Looking at some of his data logs, wierd thing is that he is running lean but not getting any o2 correction. Possible intermittent signal from the o2 sensor?

I just emailed him my latest bin files to see if that makes a difference.

dprantl

Yep, same thing I said. It must either be the O2 sensor, the O2 sensor wiring or the LH brain itself. It can't be a fuel pump issue if it goes rich at WOT.

Dan
'91 928GT S/C 475hp/460lb.ft