Going nuts.....another in-depth tuner question..$50 Paypal whoever figures it out.
10-10-2011, 04:41 AM
#22
I think everyone can confirm it has something to do with when its transferring from open to closed loop.....and from what I've learned, if its correct, open closed loop uses the MAF "mainly" while its cold and then switches over to closed loop after 122*F and then the 02's take over. (Until you go WOT, then the MAF comes back and works with the 02 sensors....not sure if thats all correct).
Question is:
Will a bad MAF make that transfer from open to closed loop....cause that missing/stumbling for that short 20-30 seconds.
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10-10-2011, 04:49 AM
#23
Man what a pain in the *** that will be to diagnose. I was told there's really no way to see if a computer is bad besides putting one in and trying it. In that case I'll have to buy one, then have my current tune downloaded into it. Then install it and put it in. But if thats not it, now I have another computer I don't need.
And again.....if the computer was bad......wouldn't it always run like crap......OR can the computer do something when it starts causing the engine to run bad.....where it fixes it by switching to a back-up mode of some sort, like mine is doing? And when my missing/stumbling stops its not like a limp mode....the engine runs perfect, strong and normal. Even the gas mileage is normal. In limp mode or when the 02 sensors are bad, the computer purposely make its real rich and its very noticeable.
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10-10-2011, 10:09 AM
#25
If the voltage is stuck low, the fuel trims will add fuel, trying to force the O2s into moving in a positive direction. If the trims max, they'll stick for a few, then go back to zero and start the same thing over. If the ocmputer realizes the O2s aren't going to move, it'll resort to open loop. Basically, just stop the trims completely.
All the guessing in this thread is really kinda silly. All you need to do is data log it while it's doing it, and there should be plenty of evidence to point you in one direction or another.
10-10-2011, 12:17 PM
#26
This is not necessarily true. When there's issues with the O2s, the computer will do different things, depending on what issues the O2s have.
If the voltage is stuck low, the fuel trims will add fuel, trying to force the O2s into moving in a positive direction. If the trims max, they'll stick for a few, then go back to zero and start the same thing over. If the ocmputer realizes the O2s aren't going to move, it'll resort to open loop. Basically, just stop the trims completely.
All the guessing in this thread is really kinda silly. All you need to do is data log it while it's doing it, and there should be plenty of evidence to point you in one direction or another.
If the voltage is stuck low, the fuel trims will add fuel, trying to force the O2s into moving in a positive direction. If the trims max, they'll stick for a few, then go back to zero and start the same thing over. If the ocmputer realizes the O2s aren't going to move, it'll resort to open loop. Basically, just stop the trims completely.
All the guessing in this thread is really kinda silly. All you need to do is data log it while it's doing it, and there should be plenty of evidence to point you in one direction or another.
Anything specific to look for....or can we just post it all up on here?
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10-10-2011, 09:50 PM
#32
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Did you check for upstream leaks (post MAF - pre cylinder head)? Unmetered air and exhaust leaks are 2 of the most common reasons for lean codes. MAF failures, faulty injectors, wiring issues (poor grounds, cracked wires, etc.), and PCM failures are secondary IMO.
Assuming you have already ruled out any sort of leak, both upstream and downstream, I would presume you could rule out the injectors as well since it's not one side or the other. I doubt it's the PCM as well. So, try swapping the MAF and going over all of the wires/connections with an eagle eye.
The only time I've seen PCM-related issues is when water was draining off the windshield and landing directly on the PCM, which would cause stumbles in the rain. Never really heard of a random issue like this that only occurs during the short time after start up.
Assuming you have already ruled out any sort of leak, both upstream and downstream, I would presume you could rule out the injectors as well since it's not one side or the other. I doubt it's the PCM as well. So, try swapping the MAF and going over all of the wires/connections with an eagle eye.
The only time I've seen PCM-related issues is when water was draining off the windshield and landing directly on the PCM, which would cause stumbles in the rain. Never really heard of a random issue like this that only occurs during the short time after start up.
10-10-2011, 10:35 PM
#33
Did you check for upstream leaks (post MAF - pre cylinder head)? Unmetered air and exhaust leaks are 2 of the most common reasons for lean codes. MAF failures, faulty injectors, wiring issues (poor grounds, cracked wires, etc.), and PCM failures are secondary IMO.
Assuming you have already ruled out any sort of leak, both upstream and downstream, I would presume you could rule out the injectors as well since it's not one side or the other. I doubt it's the PCM as well. So, try swapping the MAF and going over all of the wires/connections with an eagle eye.
The only time I've seen PCM-related issues is when water was draining off the windshield and landing directly on the PCM, which would cause stumbles in the rain. Never really heard of a random issue like this that only occurs during the short time after start up.
Assuming you have already ruled out any sort of leak, both upstream and downstream, I would presume you could rule out the injectors as well since it's not one side or the other. I doubt it's the PCM as well. So, try swapping the MAF and going over all of the wires/connections with an eagle eye.
The only time I've seen PCM-related issues is when water was draining off the windshield and landing directly on the PCM, which would cause stumbles in the rain. Never really heard of a random issue like this that only occurs during the short time after start up.
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10-11-2011, 02:24 PM
#39
I'll have to wait till late next week I guess. At least its driveable.
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