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Old 11-20-2006, 10:19 PM   #1
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Default KR at Low RPM and High Load

Since getting my Aeroforce I've done a lot of observiing. I'm getting up to 6* of KR at low RPM'* and high engine load. It'* most noticeable while cruising on the highway and climbing hills or slowly accelerating, although it also happens at WOT in the LOWER RPM ranges of 1st and 2nd and tapers off to 0* above 4k RPM'* or so.
I think my long term fuel trims are definitely screwed up. While cruising at 75mph it stays around 5.0%. As I start to climb a hill or slowly accelerate it quickly climbs to 10.x, 15.x, and will peg at 16.4% while getting up to 6* of KR until I let off the gas or return to flat ground.
LTFT'* always peg at 16.4% at WOT, although at the top of the RPM range I don't see KR.
Here'* some more data with my Aeroforce at it'* fastest data reading speed.
IAC is at 30 idle, 60 cruising and will climb to 96 or so under load.
Manifold PSI is -9.0 at idle, -5 or so at cruise, and 0.0 at WOT.
Short term fuel trims fluctuate between -3.5 and 3.5% pretty consistently
My O2 will fluctuate between 50 and 900 mv, but it will sometimes stay at one reading for a second. It will only display as fast as 4 readings per second.

Is my O2 pretty high suspect at this point? I'm at 138k and I'm not sure that it'* been changed before. I thought I've heard abnormally high LTFT'* indicate a lean condition and could cause KR. A bad O2 could contribute to this right? Could a vacuum leak cause this at all? Are my manifold PSI and IAC readings normal?

Here'* some other info about the car:
- I'm running premium fuel with the Intense PCM + advanced timing, however I can duplicate these conditions on my stock PCM as well.
-My highway gas mileage is right around 30mpg right now.
-I have no DTC'* at this point.

Thanks for the help!
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Old 11-20-2006, 10:34 PM   #2
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When you see this next time, see if it goes away at WOT. If it does you have the "97 Knock syndrome". And this throws off readings accros the board while showing KR. KR should go away at WOT and sensor readings level out.

Do not gradually go WOT, PUNCH IT! If you ease into it, the PCM locks into "retard" mode, and will show what you've been seeing.

If that ends up being the case, then its time to move on a to fix for you....
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Old 11-20-2006, 10:42 PM   #3
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I know what you're saying about punching it vs rolling into it. I'll look closer next time, but if I remember, I almost ALWAYS get some KR at the lower part of 2nd - but maybe that'* another issue. Would the "fix" be getting my fueling tuned to just add more in those circumstances that are causing KR? Like I said before though, going WOT from a dead stop still causes my LTFT'* to peg at 16.4%.
I'm not sure if I'll drive the car again tonight, but I'll leep you updated when I do.
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Old 11-20-2006, 11:00 PM   #4
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i have seen up to 8* of KR on my L27
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Old 11-21-2006, 02:39 AM   #5
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Bob, I think I know what'* happening here. Sounds eerily similar to my problems in this thread. Your KR at part throttle might be torque management from your PCM trying to regulate power to the transmission. I was seeing up to 9 degrees of KR at low RPM under load, and the problem was fixed when I went to Intense and Scott Cook took some of the torque management out of my PCM. My engine wasn't knocking whatsoever, but the TM actually shows up as KR, and even gives false knock counts that some scantools read. I wonder if that'* what is happening to you. It didn't happen to me until after I had done my cam and heads, but the symptoms sound similar. Perhaps some of the '97s do this even in stock or lightly-modded form? Here'* a cut/paste from my link above where Foghorn describes what'* going on. It'* either from page 3 or page 4.

Quote:
Originally Posted by Foghorn
Quote:
Originally Posted by big_news_1
I'm seeing as high as 10-12 degrees of KR when my TC locks in 3rd gear, under high load and low RPM. Throttle position is typically in the 10%-20% range when this occurs, though I don't believe the throttle position sensor has anything to do with the problem. It seems that this is false KR, mainly because there is no KR at low RPM in the bottom of 1st, 2nd, or 3rd gear. The problem only occurs once the car is already in 3rd gear and locks the converter. Additionally, the KR decreases and disappears as the RPMs climb, and there is no KR at wide open throttle.
That'* a very typical situation described by many people in similar circumstances to you. It'* often referred to as Flash KR because, as you say, when accelerating from a stop you don't see KR, yet while accelerating on the highway with the TC locked you get oodles of KR.

Quote:
Originally Posted by big_news_1
To sum up, this isn't just an RPM/load related issue. It only happens when the converter is locked. This issue also has nothing to do with the EGR or the cam timing, because we already reinstalled the EGR and changed the cam timing. Results are exactly the same as before we made those changes. Something really goofy is happening.
It IS an RPM/Load issue and you comments above validate the circumstances.

Quote:
Originally Posted by big_news_1
Foghorn, you might be on to something when you say I should have the PCM reprogrammed to unlock the converter sooner. But I don't want a band-aid if this is a symptom of a larger problem.

Please help, guys. I'm due at Intense on April 14th for a dyno tune, and I don't want to drive 8 hours to Ohio to find out that it would be pointless to dyno my car because I have worn-out parts installed on it. I need to get this figured out, and if I need Intense to work on the car a little bit, so be it. But it is crucial that I get this issue isolated and repaired.
The guys from Intense should be able to help you out with some custom tuning. Call Todd or Scott and explain what'* going on, I'm positive some transmission parameter changes along with Acceleration Enrichment (AE) adjustments will clear up your issues, it has for dozens of others like you.

Cheers,

Your O2 sensor voltage is supposed to bounce around from what I've been told. That sounds normal, though it wouldn't hurt to replace it if you don't think it has ever been done.

Also, are your LTFTs positive or negative 16.4%?
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Old 11-21-2006, 05:04 AM   #6
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Yes TM is normaly one of the issues, however there is NO fact to say that'* what it is.

The 97 PCM is very picky and get pickier with age.

1- a stock reflash can fix the issue
2-LT4 knock module is the best/safest fix
3-engine rebuild/inspection sometimes fixes the issue
4 full head tear down
5-a case learn sometimes fixes it

Removing TM, or upping the limits is a bad idea unless your building an all out race car, or dont care if **** breaks.

I have had this issue in ALL 13 97'* I've owned! And have solved everyone of them, personally I like the LT4 knock module with a reprog PCM and case learn. This will fix the issue 99% of the time.

-Jeremiah
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Old 11-21-2006, 04:16 PM   #7
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I agree, Jeremiah. A CASE learn or PCM reflash should be tried before removing TM from the computer. In my case, the added power from my cam/heads was probably exceeding the stock torque limits. Bob hasn't done anything radical to increase his horsepower, so it'* a different situation than what I had on my hands.

Still, if all else fails, removing TM from the PCM would probably do the trick.
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Old 11-21-2006, 04:45 PM   #8
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Can someone please explain what TM and LTFT means?
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Old 11-21-2006, 04:55 PM   #9
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Quote:
Originally Posted by MACDRIVE
Can someone please explain what TM and LTFT means?
Torque Management and Long Term Fuel Trim
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Old 11-21-2006, 09:18 PM   #10
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Ben, thanks for the link. I spent a lot of time looking over that thread before too.
Sounds like you guys have a pretty good diagnosis going. I just wanted to let you know what I "tested" for since my last post.
It seems like even after I "Punch it" as GTPboy suggested, I have to get out of low RPM'* ASAP otherwise I see KR. This means that from a dead stop and going WOT I still get some because I can't get out of the lower RPM'* quickly enough. However, if I start from a 10-15mph roll and floor it, the RPM'* jump high enough that I see NO KR until the bottom of 2nd gear again. LTFT'* are also stuck at POSITIVE 16.4% the whole time I'm WOT.

I'm already running the Intense PCM, so I was hoping that they'd have this " '97-specific issue" covered. I would have the ability to send it back in since I still have my stocker. I haven't done a case learn at this point since I was able to just switch knock modules. What would be the cost/effort of getting an LT4 module?
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