So what causes a lean spike at cruise, or cruise/slight load in closed loop? Car spikes to lean and you can feel it bog just for that moment and then it goes back to bouncing around close to 14.6 AFR.
Here's some graphs where you can see it happens.
http://www.ion-productions.com/leanSpike.JPG
http://www.ion-productions.com/leanSpike2.JPG
Doesn't seem to affect open loop any. Idle, wide open, and anything under Power Enrichment seems to work fine.
This issue began a day or two after I went and did some near-10 PSI WOT pulls, don't know how this issue resulted from it though. It still exists even post-engine swap (had a spare long block built with all new parts, forged bottom end, etc.), so it's not related to the long block itself, but a supporting item. I know it's not ignition related, that's all been recently replaced. Figured it was a vacuum leak, hooked it up to a pressurized air source and found my brake booster hose elbow where it connects to the throttle body was badly torn. Replaced that. Also, where the throttle body meets the supercharger, air was seeping through, so we RTV'd that (silicone gasket maker).
The issue remains. As you can see in the graphs above from a month ago, my TPS and such are a little jaggy... when the readings are smooth there's no problem (I noticed after we did the vacuum leak fixing the car ran seemingly fine for about 20 mins (graphs were smooth) and then it went back to normal (graphs slightly jaggy) and ran like crap).
Here's a recent crappy graph screenshot:
http://www.ion-productions.com/jaggy1.JPG
This leaning out only happens at low throttle/cruising. At idle and at 0% throttle coasting it runs perfect. Anything above about 25% throttle and it runs seemingly fine, but anything under it and it tends to cut out and bog and lean spike.
- no codes
- fuel pressure/regulator/pump fine
- not O2 related
- cat's clear
- not ignition related
- no detectable vacuum/boost leaks
So what non-engine itself/ignition/exhaust/vacuum related item would cause <25% throttle lean spiking? But not at idle or coastdown whatsoever.
Planned Attempts to Solve:
I'm replacing the TPS sometime today; I have a spare one. It has to be something at the throttle body. But I know there are no leaks anymore...
I'm also going to check for clogged injectors by doing a pressure drop test I guess. I did have an issue with these injectors when I first put them in (used Cobalt SS/SC injectors) and getting it to idle at the stock auto 550, so I just raised the idle RPM to 750. Maybe one's partially clogged or something.
Please help me fix my @!#$ gremlin problem.
I hate it. I hate breaking in a brand new built engine (only 380 miles on so far) with all of this leaning out @!#$ going on.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
I'm not sure if you can log it with your ecu, but maybe you can compare the pulse widths of your 4 injectors to see if any of them are screwy in comparison to the others (hopefully eliminating the possibility of a faulty injector).
also, can you log knock counts in individual cylinders? i can see you're not getting any kR, but it still counts knocks detected in each cylinder, and this may help point the finger at a faulty injector if that is whats causing the problem.
you could setup a histogram for the knock counts, for each cylinder, and setup a graph section for the mSec of all 4 injectors on your graph to see if any of them are seriously out of whack
Checked all pulsewidths a while back, all the same. Also I can only log knock as a whole.
Some ideas from Aleromod:
A member wrote:That is pretty strange. In each of those graphs the MAP value, TPS and IDC have almost identical curves, so I'm with you in assuming it's mechanical. Since the vacuum leaks were fixed, maybe it could be a freak thing with the IAC valve? Maybe even check to see if the sensors in the throttle body are tight.
I wrote:If the IAC was bad it would definitely affect my idle, which it hasn't. I looked at my old old scans, and my IAC position then is very similar to what it is under the same conditions now.
I'd like to run some UV reactive smoke through my system to really see if there are any leaks I'm missing.
I thought about the sensors on the throttle body being loose too. The IAC seems somewhat wiggly (not much though at all..), however the guy who sold it to me stripped the threads. I'll find a way to ensure its tightness though.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
My 02 has been that way since the reflashed PCM went in back in 05.
I'm going to swap to my old TB (has all the sensors and everything still) and see if anything changes (rules out sensors and sensor vacuum leaks).
Also will cap off all unnecessary vacuum ports on the TB.
Any other ideas on this? The above ones I posted were suggested by spyhunter. For reference, nothing changed in my tune that could've affected this. The only things that were changed in the tune from like a few weeks before this occured, and the tune I put on a few days before this occurred, were +/- 1-3 on the VE tables. I began noticing the issue after doing some post-high-RPM-tuning WOT runs on the highway. The next day on my way to work cruising at 50MPH and up to it I noticed the hesitation and lean spikes starting to occur, not as much as they are now.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
Curious question. I don't know what the stock ECU does with the MAP input, but in the second pic you posted you're showing 78kpa from the MAP. Granted I have MS-II, but when I'm at WOT I only see 99.x KPA (which you should be around 100 all motor when you're wide open). And you said this happens at cruise. Cruise and 78KPA doesn't sound right to me.
I'm assuming that even with a bypass valve some boost will still get by when you're at cruise, but that still sounds awfully high.
that was at 27% throttle and in a higher gear, so it begins to creep up to 0 boost/vac
my old wide-open was somewhere around 160 kPa or so
believe me, i've compared MAP readings between all of my logs i've ever done under various conditions, they're all the same :/
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
27% throttle at cruise? Is that normal on these cars? I was just going off of what I see on mine.... I got the 3400 thus quite a bit of low end so I see somewhere around 12% at cruise, i just figured the factory engines are probably about that since it doesn't take much to maintain speed. Just kinda threw me there.
look at the graphs.... the first one has me "cruising" at 12% throttle at 65mph.
the one graph you're talking about is me pushing the throttle more if you look at the TPS, it's not "cruise," it's slight throttle at 65mph
anyways i'll post what happens when i try stuff tomorrow
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
Oh, my bad. I thought this was all happening at cruise.
Results of throttle body and sensor swap:
52mm TB and its IAC/TPS
Graphs are smooth (no tiny jaggies). TPS percentage seems to go up a lot quicker per pedal position, far better throttle response. TPS reads 2, not 0, at idle though. Idle surges up and down slightly, sometimes gets too low and dies if revved at idle. No leaning out at cruise or light throttle. Shifting is ultra-quick and hard, as if the Abuse Mode that I turned off in my tune finally started working.
Spark advance at idle is static instead of the normal jumping around. This changes to the usual jittery advance if I disconnect the TPS while the car is running and then reconnect it.
62mm TB and its IAC/TPS
As seen above, the original data using my 62mm TB. Graphs have tiny jaggies. TPS is somewhat low per throttle position relative to the 52mm data above. Idle is smooth. Car will not die if revved at idle. Runs like crap (lean spikes) at low throttle situations such as cruise or takeoff, until around 25% throttle.
---
The idle issues with the 52mm and such could be merely due to that my tune is for the 62mm throttle body and the IAC is also not calibrated. I have a feeling that the problem with my 62mm is, in fact, the TPS, due to how drastic of a difference it seems to be from my 62mm to the 52mm one. My old original 52mm one seems to have a lot more response, oddly enough, and the TPS shows it. I will be putting the TPS from the 52mm (old) throttle body to my preferred 62mm throttle body and then putting the 62mm on the car tomorrow and see how it drives.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
Just swapped the TPS from the 52mm to the 62mm. Haven't driven yet. Here's some pictures:
RSM 62mm left, 52mm stock right
52mm intake side, notice how small the EVAP vacuum line hole is
62mm intake side, notice how big the EVAP vacuum line hole is. I think this is where the pshhhhh comes from with this throttle body when you open and close it.
52mm TPS removed
62mm TPS removed
52mm throttle plate bottom. Notice the metal ring seated right against the orange bushing or whatever it is.
62mm throttle plate bottom. The metal ring doesn't really want to budge, it sits out like that, contrasting the 52mm's perfectly seated position.
Dunno, we'll see what happens when I go drive it today.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
FIXED
Maybe only temporarily until the throttle plate wears down the TPS again but what the hell.
Using the 52mm's TPS on my RSM 62mm, now my car is extremely responsive. The TPS graph is a lot higher per pedal position now. All graphs are nice and smooth. My theory of what happened is that the TPS was reading too low. The throttle plate was open farther than the PCM thought, so there was a lot more air coming in. It tried to compensate, but failed at times, where the lean spikes occurred.
So now that the TPS is reading accurately again, it seems to have a lot more low end power and wants to enter PE a lot more (since the TPS reads higher, accurate again).
Oil change is happening tomorrow (nearing 500 miles on the new built engine) and then I'm off to tuning the low and high RPM tables and seeing what poundage I can make now.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
