Another problem.

[[ion] C2]

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.

[Alerosaint]

u and u gremlims ion....

[NickAlero2000]

yes...remember what the movie said at the end...
"when you lose power, maybe its not the fuse box...check under your counters, sinks, and your bed....because there may be a gremlin in your house"
lol

[[ion] C2]

Lol I know, Cliff says my engine's merely possessed... and the solution to this issue is simply drive like a maniac since it only happens at low throttle

Wednesday: Beat on it and kept doing near 10 PSI pulls on the highway for tuning and for fun afterward.
Thursday: The car seemed like it misfired under load like when you go from cruising to the point where it's about to downshift and the vacuum goes up near 0.
Friday: Really noticed it when I did a lot of highway driving with parts delivery for work.
Saturday: Still does it, it's like it stumbles just for one quick moment...

It's like it spikes to lean while cruising for a quick sec and you can feel it pull like you lose power for a sec and then it's back to normal. It is impossible for it to be my tune... it looks mechanical. It's probably just the engine finally going in some way... only 190,300 miles... lol

[Vinalero]

I suggest you offer that engine to science.

[[ion] C2]

This issue still exists even post-engine swap, so it's not related to the long block itself, but a supporting item. Figured it was a vacuum leak, hooked it up to a boost leak tester and found my brake booster hose elbow where it connects to the throttle body was badly torn. We 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 graph above from way back when, 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 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 cuts out and bogs and lean spikes.

- no codes
- fuel pressure/regulator/pump fine
- not O2 related
- cat's clear
- not ignition related
- no detectable vacuum/boost leaks

I'm replacing the TPS sometime today probably, I have a spare one. It has to be something at the throttle body. But I know there are no leaks anymore...

So what non-engine itself/fuel/ignition/exhaust/vacuum related item would cause <25% throttle lean spiking? But not at idle or coastdown whatsoever.

I'm 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.

[billytheman1188]

damn man......i have no idea what it is....but hopefully SOMEONE can help ya out. Seems like they are all stumped too

[01OldsAleroGt]

nothing new from Jan at Speed Industry ?

[surreal_awakening]

My buddy has a 92 Civic hatch with a B18C1 swap that has a Jackson supercharger on it. I drive the car from time to time, and for the longest time he had what sounds like the exact same issue, despite having the car tuned by a very reputable shop. It would happen just when the throttle lightly open, cruising at any speed. Scared the crap outta me the first time it happened to me. I drove it (very gently) back home and parked it and told him "I didn't do it!" After going back to the tuner a few times, and getting the shop guy in the car on the road to duplicate the issue with the laptop hooked up, they said it had to do with "throttle tip-in". I'm not sure about exactly what they altered at that point, but he hasn't had the problem since.

[[ion] C2]

tip-in's not my problem unfortunately

Originally Posted by 01OldsAleroGt

nothing new from Jan at Speed Industry ?

nah he was pretty busy last night when i was there, i had this other guy hook up the air and i listened for leaks then so did he and sprayed soapy water all over, that's when we decided to RTV the throttle body gasket, but the issue's still there

i didn't hear or feel any more leaks after that when the system was pressurized, but i do notice now when i let off the throttle i can hear a faint hiss while i'm driving, as if there's a vacuum leak somewhere

[Vinalero]

Could it be related to the supercharger intake's built in "BOV" (I call it that because I cant really think of the right name for it) You know, the device that is used to expel excess air pressure from the intake?

[[ion] C2]

it's a bypass valve, and i don't think so... wouldn't do this..

[Spilner521]

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.

[[ion] C2]

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.

I directed Jan @ Speed Industry to my corresponding thread on J-Body to hear his ideas. He tends to be super stubborn and wants things solved no matter what so I'm hoping he's got some good ideas.

[Spilner521]

Originally Posted by [ion] C2

If the IAC was bad it would definitely affect my idle, which it hasn't.

Very true...

Originally Posted by [ion] C2

I'd like to run some UV reactive smoke through my system to really see if there are any leaks I'm missing.

That's my only other idea, maybe there's still a leak somewhere that's so small it's undetectable with a normal pressure test.

[[ion] C2]

Well it's just that the leak is likely somewhere on the throttle body and you can't really hear a leak over the sound of the air entering the system from the air line.

[GA_turbo]

check and make sure the injector o-rings are sitted right, i ran into that problem before and i couldnt understand why so i checked everything that involved vaccum till i found it, i wasnt to happy about it either, it was so stupid.

[[ion] C2]

i replaced all of the o-rings a few days ago

if it's a leak it has to be pre-boost (like at the TB), as the lean spiking can occur while at 0 or 1 vac/boost too

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.

[[ion] C2]

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.


SUMMARY: Using my old 52mm throttle body and its sensors, the car does not lean out, and the throttle response is superior, TPS reads a lot higher than with the 62mm throttle body and its sensors. I will be swapping the TPS from the old 52mm to the preferred 62mm throttle body and trying it out tomorrow, as that is where I believe the problem may lie.

[[ion] C2]

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.