I've been having an intermittent problem with my AFR's.

First snap is when things are generally behaving. I drove the car into town, went into the store, and when I started the car, the AFR was crazy lean.

Have I got something totally borked in my MSQ or should I be looking at the fuel pump, fuel filter or a massive vacuum leak? Any other ideas?

Thanks for your thoughts!
Car details:
1.6
320 green top injectors
MAF delete
Brainsquirter
Begi-S, non-intercooled

 

Does the car otherwise drive normally? If you are really at 18-20:1, it would not be running at all (except for overrun).

If the car is running OK, then your problem is your WBO2 sensor. I'd be looking for wiring/grounding issues.

Helps to log injector duty cycle.

 

When the AFR is showing lean, the car doesn't pull well.

I like the idea of a crappy ground. That's consistent with intermittent nature of the problem. I'll post up a snap with injector duty cycle, and the full log when I get my other machine booted.

 

Grounds seem Ok.

One thing I did notice: when the car is misbehaving, the MAT readings are off the scale. 450 degrees?

See the attached log.... bad sensor?

 

fix your AIT sensor, MS starts pulling fuel when the temp reaches over 80°F...i think 435°F would make you a bit lean

 

I have the GM IAT sensor. Resistance at the sensor @ 70 degrees is 3430 ohms. Based on the values from DIYAutotune, this seems about right.

The connections look solid from the GM IAT to the old MAF harness. Any other ideas on what's boogering this up? Bad solder joint on the MS? Bad connection in the MS harness?

What should I dig into next?

As always, thanks for any ideas!

 

is this a diypnp or msI?

 

It's one of yours.

 

that doesnt help me.

but judging by the 12x12 tables and lack of log data, im assumg a silver MSI box with hand made harness?

 

Correct.

 

okay, then I doubt it was loaded with bad AIT firmware data...

Are you using tuner studio? did you ever move your three .inc files to your project folder?

But I doubt that's the issue as I do see the gair is adding 9% fuel when the intake temps are reporting 170*F and then pulling 33% fuel when the intake temps show 450*F.

did you start with the AFM and then remove it?


actually what's werid on the log it's stuck at 435*F, the Gair is moving around all over the place, but the MAT log isn't changing.

 

go to engine constants and turn barometric corrections off. i think that will help, but i'd make sure the ait connection is solid.

 

I am using tunerstudio.
I switched to a new laptop recently, and I don't see my three .inc files in the projects .INC directory. I'll add them now.

I've turned off Barometric correction.

I'll log another run and see if it behaves better.

What's troubling is that it's an intermittent problem, which is why I liked the idea of the bad ground or loose wiring to the GM IAT. Sometimes, the temp reads correctly, and I'm not running lean.

 

whats is is the behavior of gair (that's air temp corrections) when the ait log was pegged solid at 435.

but i think having baro on, with the settings you have it setup for is causing weird issues.

first you dont have a baro sensor, and second, the range in which baro is working is outside the realms of what could be considered atmospheric...typically you see it allowed to work with something like 90-110kPa, you have it set for 20-255kPa...that can cause issues.

 

Hey Brain,
Thanks for the suggestion.

I'm not seeing the crazy MAT temps anymore, and AFR's aren't slamming full lean.

I ran autotune for about 20 minutes against it and it cleaned up a few cells.



Jim

 

ARRRRRRRRGh.

I spoke to soon. This morning, the car was running great. I was running autotune again and the same condition happened. MAT pegged at 435 degrees.

I've attached the log I was running at the time, the temp spike happens in the last 4 minutes of the run. Any thoughts?

 

when it's showing that, you may want to read the resistance on the orange harness wire to see if the connection is still there. that's all i can think of.

 

I can't get the log file to upload. Here's a snap of the IAT flipping out.

 

914 ohms when it's whacked. I think the 914 would map pretty close to the 170 it was reading right before flipping out.

2.2k ohms about an hour after cooling down, which seems about right.

Since it's supposed to be 560 ohms at 146 degrees, that say it would have to be less than 100 ohms at 435 degrees.

I think I need to look into the harness at the Megasquirt, and perhaps at the board itself. It seems likely that these connections are open somewhere in there.

If I were to measure the resistance at the MAF connector back through the Megasquirt, what resistance should I expect to see?

Thanks,
Jim

 

doubt it's the board, the signal just goes through a resistor to the cpu.

What about the AFM connector where you attached the GM sensor? or the connection of the orange wire ot the yellow harness connector...that's where i'd look first. then the ait connector itself.