jbresee

I measured from the connector at the AFM plug back to the GM AIT, and the results were consistent with what I got directly at the GM AIT.

By the yellow wire, I assume you mean the harness at the megasquirt? I'll pull up the carpet and scope that out next.

Thanks,
Jim

Braineack

iTrader: (62)

orange. yellow is coolant.

jbresee

So I dug into the harness at the megasquirt, and found a crufty wire on the car side of the harness that connects to the orange megasquirt harness. I carved out the bad section of wire and re-crimped. The car ran fine until it got hot, then again spiked to 435 IAT.

I jumped out and checked resistance at the GM IAT, and it read .888k ohms. So that feels about right for a cool day, and certainly doesn't look like 435 degrees.

The problem is clearly thermal - when cool, the car starts and runs fine. It takes more than 20 minutes for the fault to occur.

I also noticed I had a reset in one of the logs. I'm still scratching my head on this one.

Prior to installing the megasquirt, I had a Bipes that was crimped into the harness. I'm wondering if I should go through and carve out any of the places where the Bipes was connected.

Any other ideas?

Thanks,
Jim

jbresee

Related question:

When this happens, is there a way to prevent the megasquirt pulling all my fuel off when the IAT reads 435 degrees?

Braineack

iTrader: (62)

its really weird that's happening to you, as if the connection comes loose, it goes to a fail safe mode where it just defaults to 70°F iirc. this makes me think it's providing a signal but at an extra range...hell the MSI shouldn't even be giving you a value higher than 255°

jbresee

Update on this problem:

The harness on the car side was intact. On the Megasquirt side, I found that orange wire had been borked by the strain relief barrel in the db25 connector. I cut out the bad section of the orange wire, reconnected it with a butt connector and now I have reasonable temps.

However, I have a new problem. At idle, AFR's are crazy lean (so lean that I didn't try to drive it).

I've attached a quick log of the car at idle. Any idea what's going on here?

Thanks for your thoughts!!

hornetball

iTrader: (4)

What kind of wideband is it? My earlier statement is still true here. These readings are false. You would not be able to idle at 18:1.

If an LC-1, when's the last time you did a free air calibration?

jbresee

AEM Uego, new o2 sensor.

jbresee

I think I will double check the ground on the o2.