does computer tune rich when MIL is on?
#1
11-29-2017, 06:11 PM
does computer tune rich when MIL is on?
Ive got a persistent idle missfire and poor fuel economy that im still battling and this question popped into my head.
I no longer have SAI but still have the SAI computer. so i get codes fairly often. No biggy, i just reach up and clear the codes with my sangauge, takes me 30 seconds. Well, my damn scan gauge has been busted for several months and I've neglected to send it in for a warranty replacement. So now im reduced to clearing codes far less often because its a hassle to carry around and plug in my traditional code reader all the time. therefore my check engine light stays on for far longer than usual, weeks at a time lately.
Now, the truck is staying in closed loop, but does the computer automatically default to a rich scenario every time the check engine light is illuminated? I wouldnt have thought so, i would have thought that if it were going to go into a "safe" mode it would revert to and open loop MAP.
can anyone weigh in on this?
BTW, my constant symptoms are a rough idle (But no missfire codes), and poor fuel economy, to the tune of 11-12 mpg, 14 on a very very good tank. Also have plenty of black soot on the tail pipe that appears within a couple days of cleaning off.
I no longer have SAI but still have the SAI computer. so i get codes fairly often. No biggy, i just reach up and clear the codes with my sangauge, takes me 30 seconds. Well, my damn scan gauge has been busted for several months and I've neglected to send it in for a warranty replacement. So now im reduced to clearing codes far less often because its a hassle to carry around and plug in my traditional code reader all the time. therefore my check engine light stays on for far longer than usual, weeks at a time lately.
Now, the truck is staying in closed loop, but does the computer automatically default to a rich scenario every time the check engine light is illuminated? I wouldnt have thought so, i would have thought that if it were going to go into a "safe" mode it would revert to and open loop MAP.
can anyone weigh in on this?
BTW, my constant symptoms are a rough idle (But no missfire codes), and poor fuel economy, to the tune of 11-12 mpg, 14 on a very very good tank. Also have plenty of black soot on the tail pipe that appears within a couple days of cleaning off.
#2
11-29-2017, 06:53 PM
Camel Trophy
As long as the o2’s are working, it will not. As far as your SAI, you could swap in a non-SAI ecu & bcu. Code readers are on Amazon for $5. They will also display o2 voltages semi-real time. If they are cycling normally you can assume it is not missing due to fuel mixture, probably ignition coils.
#3
11-29-2017, 07:14 PM
As long as the o2’s are working, it will not. As far as your SAI, you could swap in a non-SAI ecu & bcu. Code readers are on Amazon for $5. They will also display o2 voltages semi-real time. If they are cycling normally you can assume it is not missing due to fuel mixture, probably ignition coils.
#4
11-29-2017, 07:14 PM
#5
11-29-2017, 07:28 PM
#8
12-01-2017, 09:15 AM
What if I told you the SAI is part of the reason you are sooting up your tail pipe and running and your fuel economy is poor?
System is looking to actuate a component that isn't there anymore. A component that adds air to the exhaust, to get a proper burn. So now the O2s are reading too much fuel, not enough air. SAI is an emission device, so it wont go into a "open loop" map. (if I remember correctly. tech school was a long time ago)
I have never checked to see what it goes into when the CEL is on, but fuel economy does plummet and I do also get the smell of rich running on the occasions the CEL decides to make a visit.
System is looking to actuate a component that isn't there anymore. A component that adds air to the exhaust, to get a proper burn. So now the O2s are reading too much fuel, not enough air. SAI is an emission device, so it wont go into a "open loop" map. (if I remember correctly. tech school was a long time ago)
I have never checked to see what it goes into when the CEL is on, but fuel economy does plummet and I do also get the smell of rich running on the occasions the CEL decides to make a visit.
#9
12-01-2017, 11:01 AM
What if I told you the SAI is part of the reason you are sooting up your tail pipe and running and your fuel economy is poor?
System is looking to actuate a component that isn't there anymore. A component that adds air to the exhaust, to get a proper burn. So now the O2s are reading too much fuel, not enough air. SAI is an emission device, so it wont go into a "open loop" map. (if I remember correctly. tech school was a long time ago)
I have never checked to see what it goes into when the CEL is on, but fuel economy does plummet and I do also get the smell of rich running on the occasions the CEL decides to make a visit.
System is looking to actuate a component that isn't there anymore. A component that adds air to the exhaust, to get a proper burn. So now the O2s are reading too much fuel, not enough air. SAI is an emission device, so it wont go into a "open loop" map. (if I remember correctly. tech school was a long time ago)
I have never checked to see what it goes into when the CEL is on, but fuel economy does plummet and I do also get the smell of rich running on the occasions the CEL decides to make a visit.
Ok so the question is, under what circumstances does your cel come on? If it's completely unrelated to fuel or air metering and you still notice a rich condition then we might be getting womewhere.