Dynamic airflow, and the predictive algorithms, apply universally to gen 3-5. You should know that.
Dynamic airflow, and the predictive algorithms, apply universally to gen 3-5. You should know that.
Look at what's going on 0:36 to 1:36. That's the TB acting up, unless you've got really bad shakes. Any change in TPS is reflected in both MAP and MAF perfectly. The fluttering is due to the TB trying to match commanded based on inaccurate TPS readings. You need a new TB. DBW TB isn't servicable, so you can't just replace TPS.
That's why the TPS code. The REP because a problem is detected, and it prevents unsafe conditions like runaway.
MAF sensor...
You think it leaned out the eq ratio as a result of REP? Might make sense of the TB got stuck open and the ECU has no choice but to lean it out to lower RPMs and prevent runaway. Just trying to follow the logic.Originally Posted by SiriusC1024
No shakes...
I do not know the specific method REP is implemented, so I can't say. If this was mine I'd change the throttle body.
As far as leaning out, there's something going on at 21:03 and 23:10. That's in actual EQ, but commanded is still 1.0. Inj DC drops way down despite commanded, along with Spark Advance, so could be related. I think that's just DFCO though.
Last edited by SiriusC1024; 11-25-2023 at 01:18 AM.
With you on the DFCO at that timestamp. Duty drops to near-zero, consistent with other times where it did the same thing and the TCC mode was set to "coast," which is what it does in DFCO most of the time from what I can tell.
I'm going to replace the TB today and see if that doesn't fix ail my woes. TB isn't more than a couple years old, but had to use a parts store replacement due to schedule when it was replaced last. Thinking I'll go back to OEM this time, if it's an option. Will report on my results for documentation's sake.
Update after today. Re-installed the original MAF this morning; noticed a couple of the warm air intake hose clamps were stripped and wouldn't hold super tight downstream of the MAF sensor. Not ideal at all. Bought new clamps and will install tomorrow before I do anything with the replacement TB I picked up at the today... could a gross vacuum leak cause the issues I'm seeing?
Ran around town in the truck today for several hours with the wife, and no issues arose. After running around, I finally felt like I could quit logging. Immediately afterwards, it went back into REP. I was able to reset with my phone over bluetooth and it ran fine after clearing the codes, but using my phone to clear the codes with the MVPI3 must have somehow jacked up my data channels so the log of a follow-on REP occurrance didn't log right.
Attached are three sets of logs: the long one from everything working fine, the one immediately after the REP symbology returned with the throttle position sensor code, and one from where I was out and about minutes later and the REP symbology came back again but the channels were way slimmed down.
From your long log
Timing pull at 7:23:43:208 appears to be torque management
Timing pull from 7:25:47:884 appears to me like a DFCO but its very slow. Finally turns off the injector at 7:25:54:xx I would speed that up. If you are not using DFCO then I would investigate this reduction behavior.
Your wideband seems way off. O2 switching but the wideband saying high 15's lean. So your wot wideband reading of 12.8 is probably more like 13.8 or 14:1, not good.
Could be exhaust leak or you don't have a proper AEM wideband at the right position.
Next log, 70KB at
7:01:08:144
You are super lean and down to 2* of timing. Needs tuning or problem solving. Log the timing influencers
You absolutely can change the TPS on a DBW throttle body. The TPS is a fraction of the cost of a replacement throttle body. I have changed many of them. It is an easy, quick procedure.
I know. The TPS I bought came with the mounting hardware you need to get the new one attached to the side of the TB, but the original attachment of the TPS to the TB is rivets I would have had to drill out. Couldn't find a good quality TPS (Delco, GM, Hitachi, etc.) so I made the call to just replace the whole thing with the Hitachi I could get at my local parts store and save myself the hassle.
Since this is my daily still, I can rationalize a $250 expense easily as this truck is saving me $800+/mo. in a car note. That's what I tell my wife, anyways. Lmao!
I'll throw the tune in here as an attachment tomorrow for you to take a look at. I have dabbled in the tuning aspect of the tool, but not enough to claim to be even an amateur. Your commentary on DFCO and the delay makes sense to me. What params do you suggest to log? "Timing influencers" is too general... gotta teach me like I'm five. Haha.
As far as the WB goes... I can say the WB has been slightly leaner than stoich since day 1. I didn't like the location of the bung on these headers (speed engineering long tubes for Chevy trucks) as it is right below the trans oil pan and doesn't allow for much of an upward tilt as they suggest in the literature, but it is what it is. I will say, the values have been consistent over time (no drift like the sensor is being fouled, etc.) and were consistent with the dyno WB used by my shop.
Yes sir I know. It's not serviceable in my opinion. I don't trust the TPS suppliers for something like that. I wouldn't be comfortable with it on my ride, so I don't recommend it to others. Look at the prices on RockAuto. Dubious TPS supplier, drilling rivets, no sure way the seal is still good once installed. Then when you're done you still have a stepper motor with close to a decade of use on it and a lot of scrubbing to do.
Or for $50 more get a whole unit from an OEM supplier like Hitachi.
You got that backwards.
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All - Looks to me initially like replacing the TB/TPS and rewiring the harness did the trick. Took the truck for a test drive around the neighborhood afterwards and I see much less variation in eq ratio, which looked to me like the best indicator of where the issues were in previous logs. Was really trying to vary driving styles and listen/feel for the symptom I had before, to no avail. Good news initially.
Images from the TB replacement/rewiring and log file here (Google Photos link). I work in aero/defense and the harness looked... horrible... compared to what I am used to seeing on MIL-spec harnesses and assemblies at work. I gave some of the already-existing splices (blue butt-joint crimps) a tug and could feel some slop, indicating the crimp wasn't really holding on to the wires that well, prompting the re-wiring. Gave them a nice re-wrap when I was done re-stripping/crimping and have to say, it's the prettiest harness on the 370,000 mile truck. If this ends up fixing the problem, we'll never know if it was truly the TB or the wiring that was causing this headache.
Hope someone out there finds this useful some day! Thanks everyone for the help so far. I'll be back in here if the issue isn't solved!
Much better in the logStill a few spots where there's variation such as 8:15. Did you follow the relearn procedure yet?
https://www.youtube.com/watch?v=NAnEoMa80VY
There's also might be a Throttle Cleaned button in Scanner>Vehicle Controls & Special Functions.
I kind of wonder if just rewiring would've fixed it. What were those blue butt splices doing on there in the first place? Wires inevitably oxidize inside those. Figure out something more reliable.
Last edited by SiriusC1024; 11-26-2023 at 10:45 PM.
I kinda was wondering about the wiring being the problem myself, as I was doing it.Totally on the same page about the wires oxidizing, etc. given enough time and moisture which are givens in this environment. The pink splices are what I put on, which are 22-18 AWG. The old blue ones are for larger wires (18-14 AWG, I think) and were kinda heat shrunk like my new pink ones, but were too large to make any kind of seal on the wire insulation and prevent moisture ingress... even if they were completely shrunk and crimped right.
I was about to pull out the soldering iron and start doing it (what I consider to be) the right way with solder and good quality heat shrink, but I figured I didn't have a ton of time today. Butt splices can be good when done correctly and are a hell of a lot easier to get right while laying into the truck like I was.
I did do the relearn procedure, but am not super sure it was effective. Just the cycle of: run for 3 mins in park, off for 1 min, run for 3 min in park, off for 1 min... right? I followed the procedure that came with the TB but didn't notice any real difference between before and after. Might be worth retrying...
I plan to keep logging tomorrow to/from work (about 30 mins each way) so should have some additional info then, plus a lot more road time. Might circle back just to see what you think.
Meant to throw in there too... I didn't like the look of the un-marked TB/TPS that was on it anyways. I don't even see a part number or manufacturer on it... I figured I was already all the way in there and the TB was <$200 so I might as well throw it on.
Alright, all. So the new TB/TPS and rework of the connector failed to solve the problem. Where do I go from here? The TPS codes have cleared which is good, but the P0101 MAF code is persistant. In the attached log and relevant screenshot, you can see the stutter occur in both injector duty and spark adv, also reflected in WB reading. Initially I thought the rich condition reflected in the WB data was unburnt fuel in the exhaust from the timing being so out of whack... but now, I can see the inj duty spike as well in most of these stuttersmaking me question that assumption.
I just learned from another thread how to bump the polling rate of specific channels so I did that on inj duty, MAF/airmass, spark, and what little cam/crank sensor data I have access to. Ironically, I found that thread looking for answers on polling rate limitations, but in that same post (in the Gen IV forum) they seemed to be talking about this EXACT stutter issue. The symptoms sound like they are exactly the same to me, but the comments I got back when I asked about it occurring on my Gen III were that the issues they were referring to were strictly a Gen IV issue. Not sure what I think about that.
Would really appreciate some other input.
What next? Cam/crank sensors? MAF wiring issue? New OEM MAF?
I just realized. Where is the tune file?
The air mass spikes but maf and map don't move.
Where is the tune file? Nobody is looking in the file? *confused*
To me looks like either a corrupted memory or corrupted cell in the file, or a wrong value in the file somewhere like a keyboard oopsie.
I'd be reloading a stock file from known good and replacing the ECU if I saw that sort of behavior, outside of a polling interval related issue.
For example perhaps the tps or map voltage is spiking briefly that we dont see it in the log, because of a bad ground. Look at grounds. Look for freyed wires in the tps/map sensors. Look at shielded, an EMI issue with the MAP or TPS too close to some alternator wire perhaps. Sudden spike infinitesimal to see.
And you can disable the silly maf sensor to diagnose this issue. Disable that shit for diagnostic purposes. Simpler setups with fewer sensors dipping their fingers in the pool means easier to diagnose and easier to tune.
The yellow wire of the throttle body is always the failure........
Give it a pull....
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