Ok, so after a long delay the conclusion was the car should run as is. Despite being skeptical I gave it a try. The engine did stabilize around 1800rpm after a few minutes. Two things need addressing.
1) I'm not getting an O2 signal.
2) The fans for the radiator did not come on despite water temp reaching 214F
I haven't had a chance to troubleshoot these. Here are the DTC's that came up:
Oh, and can someone guide me on the changes needed for a blow through MAF? I have it mounted in a 2.75" tube which I think is the same as a factory inlet for a 2011 Regal, but I'm not sure. If that is the case then I think the adjustments should be minor.
Thanks. Can you elaborate how a MAF sensor is less accurate as a function of density? A MAF sensor is measuring the mass of air which is a function of temperature and pressure.
It looks like DTC's 30, 53, 131, and 135 are all linked to the O2 sensor. Apparently I have the wrong one, but it can be corrected with a little massaging. I'll fix that and give it another go.
DTC's 16 and 17 are apparently normal (crank to cam position correlation) until the PCM learns which can take a few miles to figure out. Getting closer....
As the boost climbs both density and flow go up. The maf housing can only measure up to a certain point per it's housing diameter before it caps the signal out. Sometimes it becomes an issue at the very top end of flow, sometimes it's fine it's just one of those things you watch. Larger turbos are particularly good at making mafs an issue, that's why we don't run them on boosted v8's, too many problems to overcome for a small gain.
Also these tend to be installed close to throttle bodies or ATM bov and both of those units cause disturbances is airflow which can have an effect on the return signal of the maf. Locate it 6-8" minimum from any airflow control device.
Sounds like I should be in good shape. I'm not pushing any power records here (300-350hp) and my MAF is reasonably far from the BOV and throttle. Thanks for the info.
It looks like my cal was set to turn the fans on at 228F which is a little toasty for my liking. I bumped it down to 200 so I can easily see if the fans work. I may bump it back up a bit once the car is driven around and I see how often they turn on.
I corrected the O2 sensor and started the engine. The engine ran way worse, surging and back firing. I checked the DTC's and got one for O2 sensor resistance which I understand to be a failed sensor. I replaced the sensor and now the engine won't start.
I think my issue is now tuning the MAF. In the first semi-ok running the charge pipe was blown off at the throttle body which means the MAF wasn't seeing most of the engine airflow. This was corrected at the same time I fixed the O2 sensor wiring. So, the surging and backfiring could be partially due to that?
I've attached to two recent running logs (1st: before O2 fix, 2nd: after O2 wiring fix, but likely dead sensor). A few comments:
1st: There are multiple times where engine speed ramps up. At least a few were from me pushing the charge pipe back on manually, but of course it didn't stay. This is most obvious when the engine speed hits 3900rpm (correlates with a spike in airflow).
2nd: My logger started having issues. I'm not sure exactly what caused it, but you can see there are multiple times were signal is lost (multiple channels flat lining). This makes this log far less useful then it should be, but it's what I have. Charge pipe was installed properly for this run.
I see that my fuel trims are pegged at -50. Doesn't this suggest the PCM thinks I'm rich and is trying to fix it? Or are you saying that these trims were done in error (possibly due to the charge pipe being disconnected)?
Would it not be better to adjust these fuel trims closer to zero or are these non-adjustable and I need to bump the MAF up so the PCM can use these to correct?
And just so I'm not doing something really stupid, the MAF table you are referring to is "airflow vs. frequency" right?
when the charge pipe is disconnected the trims will read pig rich (negative values) because the ecu injects for the metered air but this air isn't entering the engine...good way to diagnostic boost leaks btw
of course it is the goal to have the trims as claose to 0 as possible...but you have to get the car running first.
your log shows it is reading lean (positive values) so make it richer.
and yes the table i am talking about is the freq to airflow table.
what i also did to dial in my fuel trims for changed MAFs is i made a chart MAF freq vs total trim (LTFT+STFT)... after i roughly dialed in maf i do some part load driving, and copy the percantage result of this chart to my airflow vs freq table., than smooth out the upper cells, because you most likely will not hit all..do this 4-5 times and your trims will be nice... tuning for full laod is also needed than after this.
Weird. I see what you mean now. AFI gave me a new graph file, we'll see if that changes things. I do see the +31 on fuel trims in the chart vs. time though so at least part of the mystery is solved.
The other thing I can't make sense of is why engine speed was stabilizing around 1800rpm. This would tend to indicate a leak in the intake manifold, but I'm quite sure that's not the case. The purge valve, brake booster, and PCV are all plugged. This means the only holes left in the manifold are the nipple running to the BOV and the throttle body. Could the lack of these things be throwing off the PCM since there is now less air for a given throttle position?
Can someone share your throttle position at idle on an LHU or LNF? I'm wondering if mine is significantly more open.
Of course all this is moot until it runs; I'll give the MAF cal a try.
Well, I changed nothing but it fired right up. I'm still not getting an O2 signal so something else is wrong.
This time was really interesting. The engine speed was surging somewhat violently until it stabilized around 1500rpm. It seemed to stabilize as LTFT was increasing to ~30 again. Then it suddenly went back to zero and started surging again.
cobalt: I'm not familiar with what it is you are trying to tell me. Could you clarify?
dertobi: I'm with you on the lean. Engine stability looks to be directly correlated to LTFT, but I was seeing an equivalence ratio of 1.000 before that started ramping up. Is this equivalence ratio a fake calculation from fuel and air (not related to O2)? Do you have any idea what would cause my O2 signal to drop out at 24seconds into the log? It seems there isn't much love on this forum for a blow-through maf, but I'm still not sure why. It's after the intercooler which is going to act like a decent flow straightener, it has it's own IAT sensor, being closer to the throttle should reduce the delay error that occurs normally with a draw-through setup, and this allows me to run a vent to atmosphere BOV. Where is the down side?
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