The "SAR" car, and some lambda readings (UPDATE 3/27)
02-17-2011, 12:45 PM
#16
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Brendan, one thing I remember doing as an easy test for the MAF was to unplug it and see if it made a difference at idle- On my car, it idled better with it unplugged, but would not take any throttle. I don't know if that would tell you anything, but its an easy test....
02-17-2011, 01:22 PM
#18
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It idles pretty well, and the voltage at idle with the 02 off is .850
02-17-2011, 01:52 PM
#19
Supercharged
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Lower voltage may mean richer, and higher voltage may mean leaner. I could be wrong before or here. The reverse is true on several charts I have seen. The car does not feel rich at lower rpms. It feels lean. Obviously I need to check this. One way is to see what happens with a different MAF.
I'm confused because there are lots of charts that reverse themselves when they go away from 14.7 A/F
I'm confused because there are lots of charts that reverse themselves when they go away from 14.7 A/F
02-17-2011, 02:29 PM
#20
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So richer is higher voltage. That was my original understanding.
02-17-2011, 09:55 PM
#21
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Thanks Neil for letting me borrow the CO machine. Now I gotta find where I can get the exhaust gases before the cats.
02-18-2011, 01:47 AM
#23
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Its been so hectic, I haven't even looked under the car. Honestly.
No Cats. So... I guess I can just use the gas analyzer on the tailpipe.
No test ports.
No Cats. So... I guess I can just use the gas analyzer on the tailpipe.
No test ports.
02-18-2011, 02:01 AM
#24
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Its as if the o2 sensor's output is making the computer attempt to repeatedly come out of lean condition until 3k.
02-18-2011, 04:29 AM
#25
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How lambda control works is when O2 says lean it adds fuel until it reads rich, then it reduces fuel until it reads lean again, constantly cycling between rich and lean. I think this is actually to keep the cats happy, as they burn off during each lean cycle.
The brain shouldn't just be trying to go rich, it should be doing it.
A few minutes with a known good MAF should be an eye opener.
The brain shouldn't just be trying to go rich, it should be doing it.
A few minutes with a known good MAF should be an eye opener.
02-18-2011, 10:11 AM
#26
Supercharged
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Here's how it works in a nutshell:
The MAF measures how much air is coming in and the LH add the appropriate amount of fuel based on the MAF and the RPM that it looks up in the appropriate map. A few other parameters come into play too (temp, load, etc).
The car should be generally within a a reasonable range of stoich - I would think 14.2 to about 15.2 give or take. Then the O2 sensor should fine tune the mixture to the final 14.7 +- 0.2.
You've already unplugged the O2 sensor and it got better, but not quite right. I suspect you have two things going on here. I think there's something off with the MAF or the Temp II affecting the fueling.
I also think the O2 sensor could be suspect, but without a WideBand, or another NBO2 it's hard to tell. It just seems odd that the reading is so high.
When you punch the throttle (WOT), how does it run then?
The MAF measures how much air is coming in and the LH add the appropriate amount of fuel based on the MAF and the RPM that it looks up in the appropriate map. A few other parameters come into play too (temp, load, etc).
The car should be generally within a a reasonable range of stoich - I would think 14.2 to about 15.2 give or take. Then the O2 sensor should fine tune the mixture to the final 14.7 +- 0.2.
You've already unplugged the O2 sensor and it got better, but not quite right. I suspect you have two things going on here. I think there's something off with the MAF or the Temp II affecting the fueling.
I also think the O2 sensor could be suspect, but without a WideBand, or another NBO2 it's hard to tell. It just seems odd that the reading is so high.
When you punch the throttle (WOT), how does it run then?
02-18-2011, 10:50 AM
#27
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I understand how the system is supposed to work, what I am doing is figuring out how it's working now and why it's different.
It's probably the MAF. But I want to know that for sure before I buy another one. A trip to irvine is in the plan. I replaced the temp II as I mentioned, and there are fewotger possibilities.
I dont like Mafs - they are too fragile the way ours are designed.
It's probably the MAF. But I want to know that for sure before I buy another one. A trip to irvine is in the plan. I replaced the temp II as I mentioned, and there are fewotger possibilities.
I dont like Mafs - they are too fragile the way ours are designed.
02-18-2011, 10:51 AM
#28
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The car runs much better above 3k with the 02 unplugged.
Last edited by BC; 02-18-2011 at 11:30 AM.
02-18-2011, 11:32 AM
#30
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Steady accell with WOT (I tested that the TPS signals WOT and it does, though I suppose it could still be fried or shorted). Voltage on the 02 (disconnected, but still registering because I left the heater wires connected) sits at .845-.850. Even at idle with the o2 gone it does that. When you accel part throttle, it goes all down to .00x and .2xx then recovers to .6 just before 3k, and then settles out.
I hope that's clearer.
I hope that's clearer.