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Thread: LFX getting lots of KR

  1. #1
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    LFX getting lots of KR

    When I start to dip into the throttle the car falls on its face. Happens mostly at half to 75% throttle below 5k rpm. Only mods are Rotofab intake and Vmax TB. Tune is completely stock. Not sure what is causing all this KR. It seems to be worse when the ambient air temp is cooler. Any ideas on what the hell is going on? It's been going on for a while and I'm getting the general consensus that the intake is causing issues.
    CamaroHwy.hpl

  2. #2
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    My guess is that you need to modify your MAF table to account for the air intake differences. Your fuel trims seem to be very far off in place. You may also want to go into PE sooner than you do with the stock tune - but I wouldn't do that until you get your fuel trims in line - like I said, they are WAY off in places.

    Did you have this KR issue before you installed the Rotofab intake?

    I also have an LFX and just recently installed the VMax ported throttle body (I have a 2012 Impala - same engine though). The VMax didn't seem to affect fuel trims at all, which again points to the RotoFab as being the issue. Get your fuel trims in line first and then see where you stand.

    It also would help to log pedal position, current gear, TCC line pressure and Cylinder airmass (among other timing-related PIDs).


    EDIT: Acutally, I'm seeing a lot of misfires as well - and the "Fuel System #1 Status (SAE)" PID is reporting "OL - Fault", which I'm not familair with (see 9:56:26 in log). Something else going on here, I think, Don't think that the fuel trim issue would cause this issue - would like to hear what a more experienced tuner says too.

    Also - check for fault codes! May tell you exactly what the problem is...
    Last edited by jtrosky; 03-20-2016 at 08:04 AM.

  3. #3
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    Well I never logged with the stock intake. Didn't think there would be a problem
    I have a stick shift so TCC line pressure is out, and the two pulls I made were in 2nd and 3rd gear. It always did seem to hesitate a little during the cam profile changes but not to the point where the car completely fell on its face and threw codes. I did see the weird spikes in the fuel trims, leading me to validate others opinions about the intake messing me up.

    I have been battling issues with the car from almost day 1. took 2 different dealerships 4 times to correctly diagnose and repair a corroded main harness connection block at the firewall because water was leaking into it. It intermittently had random codes and intermittently ran rough. (Still smells musty around and in the HVAC blower). I was a f/i Cobalt tuning guru so I'm not a tuning newbie, just never worked with an LFX before, or anything newer than 2010 model year. Things have changed a LOT in these PCMs.

    Going to throw the stock intake back on, reset trims, and see if things get any better.
    2006 Cobalt SS Supercharged - 3xx whp. *Gone*
    2014 Camaro M6 - Too slow.

  4. #4
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    Stock intake back on and reset fuel trims. Even more KR now, and I get it lower in the rpm range too. Real tired of this thing...
    2006 Cobalt SS Supercharged - 3xx whp. *Gone*
    2014 Camaro M6 - Too slow.

  5. #5
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    I will say that these engins do have a lot of KR from the factory. Probably more concerning than the KR are the misfires and "Open Loop fault" issues that I saw in your original logs. Are you still seeing those two issues?

    My 2012 Impala (same 3.6L LFX engine) will show up to 9 degrees of KR and up to 6 or 7 degrees regularly during regular driving - my car is 100% stock mechanically. However, these engines do have a "Knock Learn" function which will reduce timing when KR is seen and then "remember" where the KR was (short term) so that it tries to avoid the KR from occurring again in the future. Can log Knock Learn to see this working.

    How many miles? Unless the KR is consant and repeatedly increasing once it starts, I woudn't worry too much about it (especially if you can't actually hear any knocking). It seems these engines come with VERY sensitive knock sensor settings from the factory. If you are just getting "spikes" where the KR jumps up to 6 degrees and then slowly goes down to 0, I wouldn't worry to much.

    But like i said, the misfires and "Open Loop fault" issues are a little concenring and may be a hint of a bigger problem here.

    Do you have a new log to post?

    Ive also noticed that KR seems worse for a few trips after rewrting the calibration. Make sure to review results over a few trips (cold starts).

  6. #6
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    Have'nt seen the logs but with the OL codes and all it sounds like something was broken, disconnected, or even overlooked on the sensor/wiring side of things with either the harness diagnoses or the intake swap or even the TB swap. Such an issue could definately affect fuel trims, and impropper fueling can easily cause knock. Probably not the intake, seeing as you've got it on and then off again twice I'd think you would've noticed something wrong there. The TB swap is even simpler so the same goes for that one. I would look closer at that harness & associated wiring, try to log other sensors untill you find a PID with "missing" data or data waay out of spec, or if you finally give up and have to throw in the towell go back to that dealership (after returning all parts & tuning back to stock OEM) that "fixed" the harness issue and tell them you think the issue still persists and what they repaired may have only been part of the problem or solved it temporarily.
    Last edited by Dr. Nopps; 03-22-2016 at 02:47 PM.

  7. #7
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    After not finding any sensors, fuses, or data out of spec, I began to suspect something internal. I decided to pull the intake manifold and valve covers. Didn't need to mess with the valve covers since pulling the manifold revealed everything covered in oil with the intake and exhaust valves coked with carbon/oil deposits.

    I do run the elite catch can on the passenger side PCV, but nothing on the driver side PCV. That tube coming into the intake is wet with oil, the tube coming from the elite catch can is dry.

    Since it's still warrantied i took it to the dealer and they did the top end cleaning. It feels like a new car again.

    Anyone run 2 catch cans? I have to stop this oil. ... ..

    I hate Direct Injection.
    2006 Cobalt SS Supercharged - 3xx whp. *Gone*
    2014 Camaro M6 - Too slow.

  8. #8
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    It's strange - was justing talking to someone on the ImpalaForums with a 3.6L direct-injected Impala (2012). He has over 150k miles and the intake valves aren't even that bad after all of those miles - with out a catch can. I also haven't heard any other Impala owners complain about issues related to direct-injection - not one. It's really strange how this "valve coking" issue affects some cars and not others - even with the same engine.

  9. #9
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    I do mostly city driving... maybe that makes a difference? I have no idea really. GM uses this engine in a LOT of cars, trucks, and utility vehicles so idk why the camaros seem to be affected worse than others.
    2006 Cobalt SS Supercharged - 3xx whp. *Gone*
    2014 Camaro M6 - Too slow.

  10. #10
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    you went from a cobalt to a v6 camaro? aawww mmannn. Put he stock tb back on it. put the roto fab on it. I can help. PM me.
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  11. #11
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    Hahah. Yes I took a step backwards on that one but desperate times called for desperate measures. The ss/sc needed an engine rebuild among many other things. More money to fix than the car was ever gonna be worth and I got the Camaro dirt cheap, and parted out/sold the cobalt.

    I don't have the stock TB, had to send it back as a core. Although the VMAX TB really doesn't seem to make a bit of difference as it's not a bigger bore just the inlet smoothed and honed (spiral). The Rotofab is going back on as well as some kind of clean side oil separator to go along with my dirty side catch can.

    I'm locked out of my CSS.net account, not that anyone goes there anymore LOL. lost the password to my moderator account and the admins won't get back to me. Whatever though.
    2006 Cobalt SS Supercharged - 3xx whp. *Gone*
    2014 Camaro M6 - Too slow.

  12. #12
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    Quote Originally Posted by jtrosky View Post
    I will say that these engins do have a lot of KR from the factory. Probably more concerning than the KR are the misfires and "Open Loop fault" issues that I saw in your original logs. Are you still seeing those two issues?

    My 2012 Impala (same 3.6L LFX engine) will show up to 9 degrees of KR and up to 6 or 7 degrees regularly during regular driving - my car is 100% stock mechanically. However, these engines do have a "Knock Learn" function which will reduce timing when KR is seen and then "remember" where the KR was (short term) so that it tries to avoid the KR from occurring again in the future. Can log Knock Learn to see this working.

    How many miles? Unless the KR is consant and repeatedly increasing once it starts, I woudn't worry too much about it (especially if you can't actually hear any knocking). It seems these engines come with VERY sensitive knock sensor settings from the factory. If you are just getting "spikes" where the KR jumps up to 6 degrees and then slowly goes down to 0, I wouldn't worry to much.

    But like i said, the misfires and "Open Loop fault" issues are a little concenring and may be a hint of a bigger problem here.

    Do you have a new log to post?

    Ive also noticed that KR seems worse for a few trips after rewrting the calibration. Make sure to review results over a few trips (cold starts).
    I haven't written anything to the ECM. Stock tune still. Waiting to get the issues straightened out before tuning. The car has 14,500 mi. The KR wasn't just a few random spikes. it was consistent. it would go up to 8* of KR which is the max the ECM can compensate, then it started misfiring horribly.
    2006 Cobalt SS Supercharged - 3xx whp. *Gone*
    2014 Camaro M6 - Too slow.

  13. #13
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    So did the top-end cleaning resolve your issues or are you still having the issues? I know that you mentioned that it felt like a new car after the top-end cleaning, so I had assumed that it was OK now - was that a bad assumption?

    I have substantially reduced both the severity and frequency of the KR issues on my 2012 Imapla (same LFX engine) - 48k miles. I did a few things:

    - Ran a fuel system cleaner through the tank (to hopefully cleanup the pistons a little)
    - Reduced the knock sensor sensitivity from 0-2000rpm. The reason that I did this is becuase I would see a lot of "false" KR at very low speed, low throttle, low-RPM situations and I found that the knock sensor "threshold" was set significantly lower than the LFX Camaro sensitivity threshold - only for the 0-2000rpm range (the rest of the sensitivity table was the same as the LFX Camaro). This got rid of a lot of the false KR at 1200-1600rpm. My knock sensor thresholds are still lower than the LFX Camaro thresholds from 0-2000rpm though.
    - Dialed my fuel trims in a little better for low-throttle, low-RPM situations
    - Modified my shift points to avoid "engine lugging" situations (high-speed, low-RPM situations when trying to accelerate slightly)

    I truly believe that the fuel system cleaner had a positive impact. I use to get 7-9 degrees of KR quite regularly (spikes, not constant KR), which I no longer get - now, the most I see is 4 or 5 degrees spikes and it's much less often. The shift point changes and Driver Demand part-throttle changes made a big difference as well - can is *so* much more responsive now.

    Anyway - did the top end cleaning resolve your issues or do they still exist, but the car still runs better??

  14. #14
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    The top end cleaning seems to have fixed everything for now. The techs also put in some sort of fuel additive.
    I wasn't getting low end kr. It was from about 2500 to 5000 rpm.
    The techs advised premium fuel, which I use anyways, and to spray the top end cleaner every 5k miles.
    I appreciate all the help.

  15. #15
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    these motors tend to link the richer side of the spectrum in terms of n/a afr. stops making power above 27-28 degree's of timing {pump gas} lack of tb tables cause the damn thing to ramp in and not open instantly.
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

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    So the reason why these LFX engines don't go to WOT until about 4500 RPM's is due to "missing" throttle-body-related tables?

    Just curious - I know that a lot of people have discussed that issue and I've never seen a solution to the problem...

  17. #17
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    Area, just curious, what is your reasoning for getting rid of the VMAX honed TB? Everyone swears by these things over on Camaro5 forums, although I can't see that it does a damn thing.
    I'll msg you so maybe you can help me make this thing not such a turd. I didn't buy it for speed, but ugh...

    Meh. This engine really makes me miss my old LSJ. Shoulda spent the cash to rebuild it. :-\
    2006 Cobalt SS Supercharged - 3xx whp. *Gone*
    2014 Camaro M6 - Too slow.

  18. #18
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    I recently added the Vmax ported throttle body to my 3.6L LFX Impala and honestl,y, I'm not so sure it makes any difference whatsoever... Like @Bika, I see people over on the Camaro forums swearing by it, but I'm just not "feeling" it (literally!).

    Personally, I love the LFX engine though - but the Camaro is a much larger car than a Cobalt and it's obviously not superchanged. That being said, I would take a Camaro over a Colbt any day! :-)

  19. #19
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    I regret wasting my $ on the vmax.
    As some may know, my cobalt was not exactly stock lol. That being said, the camaro is still fun to drive. Rwd is fun on the wet/ snowy roads. And the manual trans makes it much more lively than the automatic one I drove (snore). Although driving the 1LE had me grinning ear to ear. :-D Just wish I hadn't had so many problems with this car beginning with water leaks and a corroded main harness connector now the pcv..

  20. #20
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    @Bika - I'm curious - at what mileage was the Elite catch can installed? I thought that catch cans were supposed to avoid the carbon depoit issue completely?