All of the sudden leaning out everywhere
 

Hey all, finally got the car running and it's been great over the past week, yay!

Today, something new. I drive to work, and I as soon as I get off the highway, the car is running a bit leaner than usual. As in, at idle it will be about 18AFR

Also just low speed cruising around the base, I get inconsistent drivability and jerking, all the while the AFR is hovering (as though offset) by 3-4 points higher than normal.

Since I haven't touched the tune in months and months and it was driving perfectly fine over the past week, is there anything I should be on the lookout for? I haven't noticed any cracked hoses or leaks, but I literally just observed this this morning. I don't know if I should just baby the shit out of it on the commute home or just tow it. I don't have my laptop so sorry I cannot be much help.

Just probing your collective minds for troubleshooting this evening.

Things I know I need to do:
Tighten up the alternator belt, it squeals on startup
Replace Idle Control Valve (could this be the culprit?)


Maybe bad fuel pump?

do you have baro correction working right? is ts afr lining up with gauge?

Unfortunately laptop is at home. I'll check this for sure when I get home.
This is on the MTX-L

Barometric pressure history shows fluctuations of less than an inch over the past 3 days. But no change from yesterday when the car was working fine.

Do you have a fuel pressure gauge on the car? Not Miata or megasquirt specific but I've had fuel delivery issues before. I've had an in-tank filter sock pick up rust/junk and clog. It would be fine for 15 minutes or so, then start leaning out after driving a while. I've also blown a o-ring on the fpr on a returnless fuel system that did the same thing you describe. Fuel pressure would show if something like that could be the issue.

The only other thing I've seen randomly affect afr like that is a cracked/pinched/disconnected MAP sensor, but that will typically make you rich at cruise not lean.

Thanks for the insight. I don't have a fuel pressure gauge until I swap in my fuel bits. I did note that a couple days ago the fuel pump (which is usually loud on startup, kept wining even after warming up). But I didn't want to jump to conclusions and it hadn't happened since. I'll check around but aside from starting my fuel system project sooner than desired, I don't know what else to do if in case this thing is clogged.

There's also plenty of gas in the tank.

I hope to god it's not the injector(s).

Is it only lean after getting off the highway and immediately after?

I'll idle lean at highway off ramps, haven't been able to figure out why. After idling for a while it will fix itself.

It almost acts like a lean hot restart, I notice it more lately since I've switched back to 91 from e85. I'm wondering if it's not because my cruse PW is so low, maybe the injectors cook a bit while rolling down the highway for 30 miles?

I'd try and limp it home, if it were me. You'll have warmup fueling helping for a while, and hopefully ego to pull back some. Stay under 75 kpa or so and you can get away with a lot on the fueling, just doesn't always drive so smooth, melts sparkplugs...

It's actually everywhere now. Idle, cruise, slow, Swift but not loaded. Egt's are higher than normal

Might try replacing fuel filter just for shits and giggles

log first.

https://www.miataturbo.net/attachmen...ine=1459967606



I hope I can make it back, it doesn't want to stay running at idle.

So i dropped into Rosenthal and bought a fuel filter anyway and changed it out. Topped off the tank too.

This log is after the 6th attempt to get it to start without stalling out. The log starts of just idling in the driveway then took it out around the block. I didn't want to drive too much on it.

I haven't plugged my computer up to the car for a long time so I don't know what would change between yesterday and today.

What fuel pump you running, and how old is it?

Fuel pump is my guess based on your comments and the log you posted.

Did you check fuel pressure yet?

Do you have a vac leak?

are you in Arlington during the day?

Unfortunately no, I'm in Bethesda. Though if you're willing to take a peak, I can leave a key somewhere among your favorite beer and a bunny. We have lots of rabbits in the area.

Just replaced the idle control valve as well. I want to say it's the fuel pump, only because I don't know any better.

Why can't I use an NA8 fuel pump in my NA6? Can I harvest the wiring from the Walbro? Is this real life?

your MAT is showing 180°F and your MAT corrections are pulling 20% fuel.

you need to make your MAT corrections flat at 100% across the table and replace your AIT sensor.


https://www.miataturbo.net/attachmen...ine=1459992085

I may have a spare GM open element if I didn't give it to Lars, otherwise disconnect yours to drop the temp down to 70° which is the failsafe.

Try to recalibrate it first, seems really odd it's pegged like that.

probably shorted

Holy crap. I'll take a look tonight. I hope it's not shorted, but if it where, perhaps unplugging wouldn't help and we'd know for sure.

I can pick this sensor up locally from parts stores I imagine?

If you unplug it and it still says 180 then it's shorted in the wiring.

My favorite demons. Thanks guys, I'll try this tonight. In the rain. Outside. On my muddy dirt way. Hopefully I can hobble this thing together again.

yes, it's a common GM part.

You want this:

looking at advance auto parts: http://shop.advanceautoparts.com/p/c...1&prefZC=20151

Unplugged it should read like 70* or something. So unplug it. If it still reads 180 then its probably shorted.

I unplug slowly falls to 85°F

I plug it in it reads 180°F

I plug in a new IAT it reads 180°F



I re-cut/crimped the wire in case it was a bad connection, same exact thing. I'm using the old MAF wiring, so however it's run from that plug to the megasquirt is as stock. It runs ok enough with it unplugged, but I'd love to take care of this properly.

????

I'm confused

Slowly falling might be because of sensor lag.

How is it wired in?

It was soldered, i broke those and butt connected them, same results both old and new IAT sensor

I mean how is it wired to the ECU.

Stock Temp sensor wiring -> Stock ECU plugs -> Brain MS3x adapter

Think the problem is there?

Also, I did install a stereo this Sunday. New speaker cable run from the trunk to doors, RCA cables and a signal wire to the trunk . Nothing to do with the cars harness. Just full disclosure.

Tune attached, but don't know what would have changed.

doubt its a tune issue
sounds like either wiring or something is funky inside the ms, like a resistor or something ( I have no knowledge of ms intrnals, hit up Scott)

what brand/make is the new sensor? does it need different calibration/ ohm vs. temp?

If R4 somehow failed? That's the 5v pull-up resistor.

But I'd expect it to shoot up well past 180°F to like 255° or whatever the highest MS would display.

the sensor is just a variable resistor. Based on the temp of the element, it allows some of that 5v voltage to dump to ground.

What's happening here makes me think the sensor is not grounded really and the voltage, regardless of the temperature, it just going all back into the MS. But then it should failsafe to 70° like when unplugged. I dunno this one is odd.

Redo the AIT calibration for GM just in case. Worse case, I can pick up the unit and poke around.

When the ignition was off there was a spike to 350°f

It hasn't done it since. Just run two new wires to the MS?

I can drop it off any time.

I ground my IAT sensor to the post at the front of the engine with the other grounds. The other wire I run back to the ECU generally.

OK, I'll try to get a multi meter out and try a reground first.

From the 92maf wiring,
Red/green is to the ecu
Black/lt green goes to a ground distribution. I'll try to follow that and clean the grounds, then maybe directly ground the se sorry as recommended

Tried switching to two other grounds available from the maf wiring and cleaned the distribution block by the driver side firewall and the grounds at the head. There's continuity to both and the black/light green is also tied into the head ground.


No change in behavior.

Undo radio install? :likecat:

I tried removing the amp fuse. But aside from the signal wire, nothing has changed on the cars side. Power ground an illumination wire is left untouched. All speaker wire is new, signal to amp and rca. But those are all independent of the cars harness.

So the multimeter showed that the grounds are fine and the wire back at the ECU wasn't grounding out and was continuous. I snipped the temp sensor wire on the car harness side to see if it was grounding anywere and it was fine. I think it might be the megasquirt.

When completely disconnected it shows a small amount of voltage (1.8ish?), forgot to jot it down before plugging stuff back up for the day.

For now, I'll just restrict my driving to warm days without the iat.

Open the MS and look for damage.
Or wire the IAT to some other input in your MS as a test for a faulty IAT circuit.

Whats the lowest possible temp MS will readout? if its like -70°F then 180something would make sense.

My car is possessed.

I tried wiring the IAT directly at the ECU harness and the temps spiked to 350° then went back to 180°. As soon as disconnectng, it would fall as usual. I just plugged the replacement sensor back in and began reconnected the hacked up harness.

WELL.....

As soon as I got everything butt connected temporarily, there TunerStudio sat at 73°.

I thought this was the MS default/failsafe but realized the sensor was plugged in; it should have been reading 180°. I grabbed a glass of Ice Water and dunked the tip of the sensor in only to find temps plummeting.

Dafuq? I tried wiggling/teasing the wires to see if it would short again or do anything silly to no avail. I resoldered the wires back and just plugged it into the old sensor which was still installed on the coldside. Started the car right up, and it held fine. Drove around, made a couple light ~5psi pulls, watched the IAT increase a couple degrees under load, then drop back down when cruising. AFR is pretty good except for early idle. I might replace the sensor/recalibrate but the car is running again. I didn't do anything. I'm afraid to run it full tilt in case demons decide to show up again, so I'll just monitor over the next two weeks.


This case has left me stumped, I honestly don't know what went wrong or what went right. My speculation is that somewhere among the terminals, the connection was weak either at the MS3x or the ECU harness plugs. Playing with the wires teased them into place to reestablish a solid connection.



/conjecture


Thank you all for chiming in though, I really appreciate the community effort.

I think you have a marginal solder joint inside the MS.

If if acts up again he'll drop the unit off with me and i can give it a good combing.

:giggle: It happened again this morning

:(

have your cats diagnose it. they're pro's

I asked; they aren't as helpful as I'd have liked:


https://www.miataturbo.net/attachmen...ine=1460479691

Brain fixed Smurfette! <3

..so was it the ms?

Apparently. I hooked it up to the stim and saw the same 180°F regardless of the input.

I opened it up and did a visual and noticed a solder blob a resistor on that circuit that could have been the culprit. I reflowed it and went through flowing more solder on the entire board again.

Hooked it back up and it's reading fine now.

I love happy endings :likecat: