mr.skywalker

Ok, so I just finished rebuilding the engine on my 91 miata(its been a 9 month process, just fyi) and the car has been running way rich most of the time(between 9.8-11.5) but occasionally it does run great at around 14.7 when warm but this rarely happens and only for a short time.

I saw the check engine light come on so i pulled the codes, 3 and 17. 3 i expected because i had a cas go out(probably from sitting so long). 17 denotes that the o2 is not changing or is unresponsive.

Today i decided to check the output signal from the controller. I am running the stock ecu so I have wired the brown wire(simulated narrowband signal) to the ecu and have removed the oem sensor as I did not have two o2 bungs.

Now the results from my test lead me to believe it is the lc2 or controller. When the car was running, the display was between 10-11 afr but my voltage was 1.45-1.49v. I did a quick calculation and this seems to possibly be a wideband output or maybe my controller went bad. This would possibly explain why it is running so rich as it sees the odd signal and goes into limp mode(or open loop setting)

Is it possible that the sensor somehow reset to a wideband signal on this output or do you guys know of a way to test the controller?

PS: I have not made any changes to this system during the time i was rebuilding the car engine so that should not be a variable but i will check the wiring again tomorrow after work

akbloom

iTrader: (2)

Can you plug the LC-2 into your laptop and open their configuration software? From there you can adjust the output signals range.

mr.skywalker

I did think of that but I don't think I received a serial port wire when I purchased the sensor. I'll see if I can find it or order a new one, if I do have one it's about 3 hours drive away lol.

mr.skywalker

Ok, did a little more testing. I started it up and it was rich(10:1) and i checked voltage and was in 1.3-1.5v range. I tweaked the MAF a little until it reached about 14.5:1. Here is where it starts getting strange. The voltage was bouncing between 0.3-0.5v (0.5 is close to stoich in narrowband signals so maybe the 0.3 is the lc2 controller cycling which is fine).

so with that running good i drove the car about 3 or 4 miles just to see. After getting on it a bit(ran perfect during this time) the in the last few hundred feet before getting to my apartment, it started running lean(18:1). I checked voltage and it was staying below 0.3 which is correct for the narrowband signal.

I think the issue is the controller but im not entirely sure. This is one of those chicken or the egg questions, is the o2 voltage what causes it to run rich(tripping out the ecu with a high voltage causing limp mode) or is it running rich and causes the o2 to read high voltage.

My idea is to weld in another o2 bung and run a stock o2 and the wideband. This way if it is the controller the car will run right and the wideband would simply be a monitor(until megasquirt goes in). I just hate the idea of having to weld in a bung because my welding equipment is 3 hrs away and I am to cheap to find a local welder when i can very well do it myself lol.

Does that sound like the right process to figure this out? I am not the best with electronics

akbloom

iTrader: (2)

You can guess all you want and weld in new equipment and swap in the old sensor, but none of it will confirm wether or not your wideband is configured properly. You need a serial cable and a laptop.

mr.skywalker

I completely understand that you dont just swap parts and hope for the best. The reason i am considering this is that the results point to the fact that the sensor is working properly(voltage vs o2 reading seems correct for a narrowband and the car runs like the o2 reading suggests, when rich it bogs and blubbers and lean it surges and weak) but im hoping that it is just that sensor is what caused this as it would be a cheap fix to put a stock o2 sensor for the time being.

I have looked for the cable online but the ones that are available separately dont seem to be the right ones for mine? anyone know where to look or order one?

mr.skywalker

Ok, I finally got around to putting in the second bung and both sensors(all said and done was less than $35 so i figures it was worth the shot). Anyway it looks like it is working much better, the afrs stay steady in the 14.5-15.2 range(except for over 4krpm it drops to about 11 but thats bc its OL and i have 305 injectors so it doesnt trim fuel. So its good except the wideband didnt want calibrate last night but no problem this morning.

But now I have another issue, I may need to start another thread for this but when I open it up a bit and go into boost(Im staying below about 3psi until I can get megasquirt in) but when I let off for the shift the car just dies. It is like the spark dies, leaving it gear and pressing the clutch in and popping does not light it off. The only way to restart it is to kill ignition, put back to the on position and if the car is still rolling bump starting it or if stopped just start like normal. After doing this it starts up perfect and drives fine(until it hits boost again) Im probably just going to disconnect the waste gate until I get MS installed.

The only thing i can think of right now that may kill spark (and has a correlation with boost) would be the MSD timing box if there is a bad connection. I will check these connections too.

ryansmoneypit

iTrader: (6)

This is why aids are frowned upon.

mr.skywalker

Trust me I hate running band aids but when i was having trouble getting my MS working the guys on here were the worst help even after i spent weeks doing research and even offered a payment if they would be willing to sit down and teach me or set up a file for me.

At least now I have a friend from work who is Electrical Engineer(Engine programming too) and he has volunteered to help me so maybe Ill be able to get away from these bandaids soon.

And a little update, i think its something with the just letting the rpms drop to quick(probably the damper and/or tps setting). If i keep a little throttle through the shift it runs fine, even in boost

mr.skywalker

Checked engine codes and have codes 2 and 3 stored, both are CAS errors from what i can see. I know my cas connector is pretty messed up. Its old and stiff so the clip broke and i had a few times that i had to jiggle the wires to get the car to run. I ordered a new plug (also injector plugs for the same reason) about a week ago, but i think it will be while because they are coming from japan. I think this is the issue because it cuts out so hard it feels like the ignition is cutting out rather than fuel.

Sorry about updating this thread so much but i like to document everything so if someone else has this issue in the future hopefully it will help them. Nothing is worse than finding a thread that the OP had exactly the same issues and never found a solution or at least didnt post what it was

mr.skywalker

Well i fixed the connection issues but still had the same problem.

Once when it cut out on me i came to a stop and surprisingly it was actually still running, just the AFR was pegged at 22.4 so it just had no power at all which made it feel like it was dead and could not rev up even in neutral and not moving.

So that said it was a fuel issue and i jumpered the FP to GRND in the diagnostics box and with doing so the issue has completely gone away and i tried to make it repeat about a dozen times, not one hiccup. So now i just need to determine if it is the AFM or the relay