BlazingTrails
Member
- Apr 27, 2014
- 19,409
do I need to reset the ECU or clear codes when replacing O2 sensor?
- Thread starter sunliner
- Start date
Welcome! For me, coils are on an "as needed" basis. They don't need changing out as a preventive maintenance item. I carry one only as a spare.
Thanks both. Will hold off then and see what the codes say after the sensor change and TB clean.
Back to OP's question in post # 24 ..
Sunliner, Was the AC running when you recorded those readings..Normal AFGS in N/P w/o AC s/b around 5.2 Gms/sec with TPS at 14.5 % and RPM at 610 with a vacuum of 33 Kpa. But with AC (compressor running) in N/P the PCM opens the TB to 16.1% to keep RPM constant at 610 that increase AFGS to 6.1 vacuum drops a bit to 39 Kpa everything else s/b the same.
NOW you readings showed RPM at 625 w/coolant at 208, and the other readings TPS %, AFGS and Kpa are close assuming the AC was on, if not then your AFGS, TPS are high and vacuum is low.
By the way my ST trims are -1.6% and LT trims are -1.5 at idle, I do run my engine 10* cooler than stock, could be why it's pulling a bit of fuel. Your trims show the PCM is adding 17% more fuel to keep things straight. And is is doing a good job as the ST trims are +0.7% just about a perfect burn.
I asked about fuel pressure a while back in your other post, what are you running at idle ? You eliminated the O2 so I believe you are either either getting un-metered air (not passing the MAS) or not enough fuel.
Sunliner, Was the AC running when you recorded those readings..Normal AFGS in N/P w/o AC s/b around 5.2 Gms/sec with TPS at 14.5 % and RPM at 610 with a vacuum of 33 Kpa. But with AC (compressor running) in N/P the PCM opens the TB to 16.1% to keep RPM constant at 610 that increase AFGS to 6.1 vacuum drops a bit to 39 Kpa everything else s/b the same.
NOW you readings showed RPM at 625 w/coolant at 208, and the other readings TPS %, AFGS and Kpa are close assuming the AC was on, if not then your AFGS, TPS are high and vacuum is low.
By the way my ST trims are -1.6% and LT trims are -1.5 at idle, I do run my engine 10* cooler than stock, could be why it's pulling a bit of fuel. Your trims show the PCM is adding 17% more fuel to keep things straight. And is is doing a good job as the ST trims are +0.7% just about a perfect burn.
I asked about fuel pressure a while back in your other post, what are you running at idle ? You eliminated the O2 so I believe you are either either getting un-metered air (not passing the MAS) or not enough fuel.
I honestly can't remember...I would bet that the A/C was on then. I will do another recording without AC on if that will help.
I have not checked fuel pressure yet...I know I should, and will but I'm a wuss...everytime I get the end of the gauge wedged in the tiny space allowed, gas sprays everywhere and I pull back before I get it threaded. I know a little spray is normal but it's just one of those things that spooks me.
The freeze frame I grabbed last night showed the MAF was reporting 6.75 GR/SE at the time the DTC last set...is that not too high? or is it a case where the system is pulling more air d/t a possible leak?
Of course, while driving today, the light went off today and the code has disappeared. it'll be back though. the truck is possessed.
I have not checked fuel pressure yet...I know I should, and will but I'm a wuss...everytime I get the end of the gauge wedged in the tiny space allowed, gas sprays everywhere and I pull back before I get it threaded. I know a little spray is normal but it's just one of those things that spooks me.
The freeze frame I grabbed last night showed the MAF was reporting 6.75 GR/SE at the time the DTC last set...is that not too high? or is it a case where the system is pulling more air d/t a possible leak?
Of course, while driving today, the light went off today and the code has disappeared. it'll be back though. the truck is possessed.
Mounce
Member
Hook up gauge, put relay back in, start her up!Here's another recording..went for about a 10 mile drive, then back to the house...AC off during recording.
http://vidmg.photobucket.com/albums/v280/sunliner/CAM00968_zps9f0d77a3.mp4
http://vidmg.photobucket.com/albums/v280/sunliner/CAM00968_zps9f0d77a3.mp4
bobdec said:
in case the link above doesn't work
http://smg.photobucket.com/user/sunliner/media/CAM00968_zps9f0d77a3.mp4.html
http://smg.photobucket.com/user/sunliner/media/CAM00968_zps9f0d77a3.mp4.html
Everything looks good, RPM around 600, air flow around 5 Gms/Sec , vac at 33 Kpa , TPS% around 14, coolant a bit hot at 215* F, but that is not a concern. LT trims say PCM is adding 18% fuel above what the fueling calculation has determined, at +20% it will throw the DTC. . Problem seems to be at 2500 RPM also. As I mentioned a small vac leak would disappear or get much better at higher RPM. At 2500 RPM your ST trims (actual burn at O2) went to + 1.5 from the -1.5 at idle. That says the 18% LT correction value over corrected a very small bit, but nothing significant . I'm still wrapped up on fueling, and staying away from injectors as a weak one would most likely throw a misfire code and not be as bad as 18% lean..
+1 on Mounce's info in post #46, that will eliminate the fuel spillage concern. .
+1 on Mounce's info in post #46, that will eliminate the fuel spillage concern. .
The ambient temp is stupid hot last few days, it was probably still 101 outside. Just glad the fan clutch works!bobdec said:
I'm putting the fuel pressure gauge on when I get home from work; will post back with results. I believe the pump,regulator,filter and all are in the tank on this vehicle so if that's what it is, I gotta take it in as I'm not comfortable dropping the tank, but at least I'll know.
allrighty then.
Key on , engine off 52 Psi
Engine on...the needle flutters like crazy between about 58-62 (will put a short video up if you need to see it)
Engine off , held 56 psi for at least 5 minutes
goofed around another 5 minutes or so and relieved pressure via the gauge valve into a gas can. no more would run through the tube and still had a couple of spurts when I disconnected the line.
Key on , engine off 52 Psi
Engine on...the needle flutters like crazy between about 58-62 (will put a short video up if you need to see it)
Engine off , held 56 psi for at least 5 minutes
goofed around another 5 minutes or so and relieved pressure via the gauge valve into a gas can. no more would run through the tube and still had a couple of spurts when I disconnected the line.
bobdec said:
Mounce
Member
I would say fluttering due to the RPMs bouncing ever so slightly. (which they do)sunliner said:
ok...so normal then? I just remember testing this on my Blazer waay back when and I thought the needle stayed still then.Mounce said:
Mounce
Member
I'm no pro bud, but if I saw that on my ride I wouldn't be concerned and would blame it on the RPM fluctuation. Does it hold pressure with the engine off?
yep
Engine off , held 56 psi for at least 5 minutes
goofed around another 5 minutes or so and relieved pressure via the gauge valve into a gas can. no more would run through the tube and still had a couple of spurts when I disconnected the line.
once again, I managed to shoot sideways...but here's a short vid
http://smg.photobucket.com/user/sunliner/media/20140825_175056_zps09e91be5.mp4.html
Engine off , held 56 psi for at least 5 minutes
goofed around another 5 minutes or so and relieved pressure via the gauge valve into a gas can. no more would run through the tube and still had a couple of spurts when I disconnected the line.
once again, I managed to shoot sideways...but here's a short vid
http://smg.photobucket.com/user/sunliner/media/20140825_175056_zps09e91be5.mp4.html
Mounce
Member
Okay, I didn't realize that the needle was jumping that quick but I still feel like it's okay. Imagine an injector opening and releasing pressure in the line while the FPR is trying to keep it level so it'll dump a little extra fuel in the line then the injector closed and the pressure jumps back up to where it started or a little more and quickly followed by another injector opening. This all happens very quickly though, like the needle is moving. I hope one of the guys with more experience chimes in though, I don't have the experience to feel safe saying "yeah, you're good to go."
this truck will never be 'good to go". your explanation makes sense though. I'm going back to looking for air/vacuum leaks tomorrow. maybe clean the MAF sensor for the 100th time.
I did note that my resonator only has one bolt holding it on but it looks like the air passes through a closed section of the assembly so that shouldn't mean anything.
I did note that my resonator only has one bolt holding it on but it looks like the air passes through a closed section of the assembly so that shouldn't mean anything.
Mounce
Member
Only one bolt that holds it to the top of the motor? That should be fine. For the vacuum leak, mainly focus between the MAF and the throttle body. Also, don't forget about the crankcase breather hose under the resonator box, make sure it's connected. If it comes down that you're sure it's an air leak and you can't find anything between MAF and TB, the intake manifold bolts would be suspect as they have been known to back out on their own, but open that can of worms if it's the last idea, the bolts aren't easy to get to. Btw, most of this is assuming you have the 4.2, I'm on tapatalk and can't see vehicle info.
thanks. it is the 4.2. I checked the intake manifold bolts, but not sure if I got all of them. I keep thinking I can't have too much of a leak with the vacuum readings I get ,I guess it could be different when I'm driving vs idle, but the freeze data I have indicates that I was at idle last time the code set. going to recheck the EVAP side of the house too..that could be a case of having to catch it in the act.
Mounce said:
another question...grasping at straws probably....if I had an EVAP System Monitor test that was stuck in 'incomplete" status, would that make the evap sys hang open...maybe letting air in?
Mounce
Member
just the P0171.
my evap codes went away ever since I replaced the vent solenoid....but that's when the 0171 started.
my evap codes went away ever since I replaced the vent solenoid....but that's when the 0171 started.
Mounce said:
Mounce
Member
Okay, and have you replaced the O2 sensor(s) that the code is fussing about? If you have, next would be to check the exhaust manifold for cracks if you haven't. I mentioned this is another thread recently but I can't remember if it was this one or not and I don't have the time to read all 70 posts in this thread right now so I apologize if I'm barking down a road that you've already traveled.
no problem..thread IS getting long, but I think we're close to an end. to answer, I did replace the upstream O2 sensor. Have not yet looked at the exhaust manifold. I rechecked vacuum with a gauge and also doing the old carb cleaner test. only possibly weird thing I found was that, with the truck idling, if I pumped the brakes repeatedly (really way more that you normally ever would) I could make the engine momentarily speed up. I don't think that means much.
I'm going to recheck one evap solenoid...wondering if it's opening sporadically when it shouldn't, but closing up at the times I'm checking vacuum. and will look at the exhaust manifold. after that...I'm surrendering and taking it to the shop. Thanks everyone for the advice. Really, if nothing else I have learned quite a bit during this little adventure.
I'm going to recheck one evap solenoid...wondering if it's opening sporadically when it shouldn't, but closing up at the times I'm checking vacuum. and will look at the exhaust manifold. after that...I'm surrendering and taking it to the shop. Thanks everyone for the advice. Really, if nothing else I have learned quite a bit during this little adventure.
Mounce said:
Mounce
Member
I'd get to checking the exhaust manifold soon. It's a pretty common problem and tends to lead people on a wild goose chase like you're on now lol.
And you're welcome, we don't mind, we're here to help! Also, pardon my spelling mistakes, I've never seen myself make so many typos in one day throughout my last few posts lol.
And you're welcome, we don't mind, we're here to help! Also, pardon my spelling mistakes, I've never seen myself make so many typos in one day throughout my last few posts lol.
I don't know if anyone is still following this...but I pulled the MAF sensor to replace. I disconnected the neg battery cable during this. after I reconnected the battery, the AC compressor would not come on. I drove the truck around , made a few stops and probably the fifth time I started the truck again, the AC comes on just like nothing ever happened. Never noticed this happening before...
BlazingTrails
Member
- Apr 27, 2014
- 19,409
IllogicTC
Member
- Dec 30, 2013
- 3,452
If the P0171 showed up right after replacing the vent solenoid... have you verified your fix was complete? As in both surfaces clean before installation, and bolts tightened to spec? The wiring should be one-way with the usual connector, so I wouldn't think that'd be involved.
Agreed..one electrical connection and one vapor line from the solenoid to the canister. checked and rechecked. drives me nuts that the problem started right after that work was done, but everything looks tight.
IllogicTC said:
Just to make sure , you said ".one electrical connection and one vapor line from the solenoid to the canister." Assume you also connected vacuum source hose from TB.
there's only one hose:http://shop.advanceautoparts.com/p/bwd-vapor-canister-vent-solenoid-cp512/20470245-P
bobdec said:
pulled the throttle body off today... was gonna change the intake gasket but decided not to. found a nice layer of what looks like oil on the inside of the intake manifold. this just gets better and better!
BlazingTrails
Member
- Apr 27, 2014
- 19,409
regarding LT fuel trims...let's say that I get the problem fixed. will the LTFTRM start going close to zero immediately, or might it take a few drive cycles and/or miles to trend down to normal?
IllogicTC said:I've read threads where people are saying it's impossible, as the higher-than-atmospheric pressure in the exhaust manifold would push gases OUT not draw them in. But to that, I say it's acting on a sort of Venturi Effect, the draft of the exhaust gases passing down the manifold may be pulling some fresh air in, or not all the exhaust gas is getting accounted for if it is indeed escaping.
IllogicTC
Member
- Dec 30, 2013
- 3,452
It is. There is no actual PCV valve, it's just a hose that runs to the manifold and breathes deep. I can't remember, but there was an explanation for what would be considered "excess" floating around here or at the OS at some point, I believe the top hose that plugs into the resonator on the bottom front had something to do with it, something like if water vapor collects in the air and cools over time it can pretty much act like a plumbing "P-trap" not allowing gases to flow or something.BlazingTrails said:that's pretty normal bro.
update...could not see any obvious manifold problems.
This past Sunday, I replaced the MAF sensor and figuring nothing to loose I replaced the throttle body gasket. pulled power to the computer during the change. Even said a prayer that the thing would start acting right. Went out Monday for a long drive and started the usual home-school-job routine on Tuesday. As of today (Thursday 4 September,) the check engine light is off.
I plugged in the scanner today after driving around town maybe 25-30 miles just to see the data. At idle, LT trims are around 8 or lower, ST trims look to be constantly negative...during the time I watched they ranged from -5 up to +0.2.
My theory...tell me if I'm wrong..maybe the PCM is still learning the new set up with the sensor (?). Truck drives well, and remember my LT trims had been as high as 20-25% when I was throwing other parts at the thing, so something's improving.
This past Sunday, I replaced the MAF sensor and figuring nothing to loose I replaced the throttle body gasket. pulled power to the computer during the change. Even said a prayer that the thing would start acting right. Went out Monday for a long drive and started the usual home-school-job routine on Tuesday. As of today (Thursday 4 September,) the check engine light is off.
I plugged in the scanner today after driving around town maybe 25-30 miles just to see the data. At idle, LT trims are around 8 or lower, ST trims look to be constantly negative...during the time I watched they ranged from -5 up to +0.2.
My theory...tell me if I'm wrong..maybe the PCM is still learning the new set up with the sensor (?). Truck drives well, and remember my LT trims had been as high as 20-25% when I was throwing other parts at the thing, so something's improving.
