So I found this doing homework on my problem so I started looking at my PCV system and the purge line. No change disconnecting anything....figures right. I noticed though on the pcv system that depending on how I moved the hard plastic line I could hear an audible change in the airflow going in. Noticed that the angles of how it leaves the valve cover and goes into the intake manifold are similar. Detached the line and flipped it. Could tell it was sucking so much more air. So here's my new trims at idle and it holds that, I also introduced vacuum and ltft instantly responded into the positives which I took as a good sign. I also remember vaguely messing with that line, can't remember flipping it but that's when it turned off almost a year ago so idk if I flipped it then
Persistent p0172 and p0175
- Thread starter MBS1994
- Start date
I do too but I've said that about 9 times on this thread haha.....I'm gonna give it a drive tomorrow but I haven't seen trims respond like this once. Fingers crossed
Negatory ghost rider. There's a tear in the soft plastic line that connects the valve cover to the plastic line that runs into the manifold. It was a vacuum leak I was hearing. When I put my finger over the tear my numbers go rich again.
?? I don't understand this. picture of the line / area maybe... the L6 doesn't have a pcv valve. Perhaps your valve is stuck open.
I was probably a bit optimistic and didn't look close enough at the your graphs. The idle one appears better than previous posted "vacuum open" graphs. It shows a constant LTFT and a waggling STFT as expected. The "run" graph appears to indicate an issue but opposite to earlier "problem report" where you were indicating "high negative value". My comment at the front of this post still applies... I don't understand your previous post.
One other thing, are you getting any codes currently?
I am still thinking you have a MAP problem.
I was probably a bit optimistic and didn't look close enough at the your graphs. The idle one appears better than previous posted "vacuum open" graphs. It shows a constant LTFT and a waggling STFT as expected. The "run" graph appears to indicate an issue but opposite to earlier "problem report" where you were indicating "high negative value". My comment at the front of this post still applies... I don't understand your previous post.
One other thing, are you getting any codes currently?
I am still thinking you have a MAP problem.
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So where I'm pointing is where it starts and then it goes directly into the top middle of my intake manifold. I put a brand new map in this weekend, no more junk yard parts, and no change so maybe I need to check the voltage again. That picture I posted that had me on this path also mentioned oil so i might try that as it probably needs to be done anyway but don't expect any result. Was also debating on new plugs.
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OK... thanks. I am still unsure of where you are at. Look at the title... it indicates that you have p0172, p0175 codes. However your last post of trims don't appear to be anywhere near those types of codes as the "tail end" of the third graph show that your system is presently running lean and is trying to correct with more fueling. This is the opposite IF I understand your data, hence my confusion.
The last post of trims is when I thought I found it but that was a vacuum leak on the pcv line so it was false
ok... but still confusing... post a graph of your current trims at idle and at constant throttle with everything properly connected.
Sorry works been busy and by time I'm off it's dark and cold so I haven't been to eager to mess with the trailblazer. It crossed my mind though that when I did my headers like I said it was rushed for a move. I didn't connect my front o2s right away and right after we moved the ignition switch went bad so I replaced that and mailed off the ecu to tune it and delete vats. Obviously since there was no o2s hooked up I couldn't get trim levels to set the current codes. I'm really leaning towards the tune at this point since I am pretty confident I never had these codes before I messed with the exhaust.
that's ok... where ever you head, I hope it gets resolved ... and since you don't have cats, there really isn't a worry, just a thorn in the side.
I have 2 hi flow cats. I'm gonna take them up on dialing back the tune and see what it does and if not then mechanic time
Just a random update. Went to pull the ecm out today and found two yellow wires that were broken. Gonna try to see if I can figure out that problem before I mail it out
I'm running errands at the moment but it's two wires where the harness attaches to the ecm.
the MAF sensor signal is on pin 11 of the C3 connector (bottom connector in the stack)... is that bundle that you found the yellow wire in?
No it was c1. I'm still planning to send the ecm back for a retune but will check the wires as I do it to make sure
its kind of unlikely that there is a "missing" MAF type connection as you would coded with a fault point at that particular unit.
Dropped the ecm off at UPS today. I will update when it comes back just incase someone else has a similar problem later down the road.
Still same codes....I don't think I can keep chasing this problem. As much as I enjoy the car I've put to much money into it as is let alone whatever else would be the next possible try.
:-( I think your problem is still associated with the MAP and wiring there in. I would suggest that you do a vacuum test on the sensor (kept attached to the harness and reading its output with the app). Then compare this with what your vacuum pump / gage is telling you. They should basically align for a wide range from no vacuum, to partial (ie. 10ish) to "full" (ie. 18-20 ish). Repeat the test a few times to confirm consistency.
NOTE: this is the great test the TJbaker57 used / stated.
NOTE: this is the great test the TJbaker57 used / stated.
Crank position sensor? I found a old one in the glove box and who knows when it was replaced. Anyone think maybe that could be it?
Mooseman
Moderator
Maf, map, retuned, o2 sensors, vapor purge and vent solenoids, repaired some wire on the map, cleaned throttle body and swapped for a known good one, cleaned injectors, replaced intake manifold gaskets, replaced a vacuum hose I found torn, verified fuel rail pressure at 58. I replaced the the crank position sensor this morning because I was reading it can mess with timing if it's bad because it says the crank is in a different position than it really is but still nope. Might be a thing or two I'm forgetting because it's been a lot
Mooseman
Moderator
I hate just throwing parts at it but the only thing left is the injectors themselves unless someone else has any ideas? Sorry if we've asked this before, what do the spark plugs look like? If it was just one bank running rich I'd believe one bad injector but to have several on both banks would be unusual.
If it's running rich, two things might affect it. Too much fuel or not enough air or the PCM thinks it's running rich because of wrong parts being used or bad data it's receiving. What brand/type spark plugs are you using. Same for the O2 sensors.
Another hail Mary, is the exhaust in good condition? Blocked exhaust or cats might be throwing the sensors off. Tried a backpressure test?
If it's running rich, two things might affect it. Too much fuel or not enough air or the PCM thinks it's running rich because of wrong parts being used or bad data it's receiving. What brand/type spark plugs are you using. Same for the O2 sensors.
Another hail Mary, is the exhaust in good condition? Blocked exhaust or cats might be throwing the sensors off. Tried a backpressure test?
I believe the o2s are Bosch amd spark plugs I d9nt remember but something about triple platinum is ringing a bell. Only thing I can think at this point that I did to both banks is spark plugs and idk if it would impact it but I remember taking out my pushrods and rocker arms a while back because I was anticipating pulling the heads, I can't remember if that was around the same time I first got the codes or not. Maybe spark plugs? I have a buyer lined up for it but I'd hate to not solve it and keep it
Mooseman
Moderator
The LS engines are less finicky than the 4.2 however I would still favour OEM parts over aftermarket. OEM spark plugs are supposed to be ACDelco iridium. Haven't heard anything about Bosch O2 sensors but again, ACDelco are favoured here.
As mentioned, you should concentrate on the MAP, MAF and check your exhaust.
As mentioned, you should concentrate on the MAP, MAF and check your exhaust.
They (spark plugs) are ac delco 41-962. Some places say they don't fit and others say they do. I keep seeing debates on 962s or 110s.
Mooseman
Moderator
The 41-110 aren't even listed for any vehicle the same year as yours (2015+). For your 2006, should be 41-162, which is listed as the GM original part. I'd stick with those when in doubt.
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you need to post new graphs of your trims (especially LTFT) as there has been so much time and things done that I for one don't really understand what you are "chasing" at this point.
ok thanks... :-( still ugly. I see the ltft has a "plateau" of about -10ish which seems like some richness that the system is trying to take out most of the time.... BUT the spikes are disturbing and are likely causing the coding. During those "spike times", do you recall what is happening with the engine... meaning, are you changing throttle, gearing (neutral / park) or are these just idle charts? IF nothing is happening in terms of engine / driver "activity", that is your problem.... I don't believe ltft move that significantly and it likely points bad things around the sensor, my guess again is the MAP. Either itself is bad (my experience says it is possible to have bad parts ... that's why the suggestion of doing the vacuum test on the sensor) or the wiring to it is "marginal".... again, the test may show something.
You appear to be getting pretty good at the data app. You might want to plot the ltft on one graph and the vacuum (absolute) on the other to see if there is correlation. Not sure how fast things will be polled but potentially it costs you nothing to try.
You appear to be getting pretty good at the data app. You might want to plot the ltft on one graph and the vacuum (absolute) on the other to see if there is correlation. Not sure how fast things will be polled but potentially it costs you nothing to try.
It improves under throttle, seems like it goes down also when it does go into park and up when it first goes into drive. The random dip downs are while it sits stationary but its quick. I pulled my plugs, cleaned them, and regapped them (a few gaps were wrong). I noticed some wires I had to fight to get off while others would pop right off so gotta make sure they are all tight when i reinstall. I need to check out a vacuum gauge to test the map but it's been frustrating buying more things to test when I've already spent a decent amount already and haven't made progress.
don't buy any more... do the "free test" that suggested... graph your ltft and the absolute vacuum and see if anything shows correlation.
Oil smells like gas real bad. I've read that can cause a rich condition but can also be caused by a rich condition amongst other things.
Mooseman
Moderator
I've seen that in '90's cars that would fail to start in damp weather and would have to change the oil because it got so full of gas from trying to start it. If you can smell a definite gas smell in the oil, I would change it to eliminate this as a source of any extra fuel vapours causing rich conditions.