Stutter/Hesitation between 1500-2000rpm's
05-02-2008, 12:22 PM
#1
Stutter/Hesitation between 1500-2000rpm's So im having a problem with my car right around 1500-2000rpm range. It has a slight stutter/hesitation that is not real bad but is really anoying. We tried adding about 6 degrees of timing in the surge zone, but there was no change. When the tune was in open loop, the problem didn’t exist but the car ran real rough. All my mods are in my sig below.
Thanks
Troy
Thanks
Troy
05-02-2008, 11:21 PM
#4
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So im having a problem with my car right around 1500-2000rpm range. It has a slight stutter/hesitation that is not real bad but is really anoying. We tried adding about 6 degrees of timing in the surge zone, but there was no change. When the tune was in open loop, the problem didn’t exist but the car ran real rough. All my mods are in my sig below.
Thanks
Troy
Thanks
Troy
Hi Troy. I'd like to help out but I am confused. A "slight stutter/hesitation" is really annoying and bad to me.
The car running "really ruff in OL" is a real big bag of door ***** banging against my temple as well.
Can you elaborate? What software are you using? What fueling / airflow measurement methods are you employing? (OLMAF, OLSD, CLMAF, CLSD) What bar MAP sensor are you running? What type of WB02?
I'd like to help, just need more info.
05-03-2008, 03:02 AM
#6
Nope! that MAF is clean and working properly
Nope! Everything is fine during WOT
I meant that it's not a Oh my god I cant drive the car problem. It just has this hesitation in it that I can feel and really annoys me.
Nope! Everything is fine during WOT
Hi Troy. I'd like to help out but I am confused. A "slight stutter/hesitation" is really annoying and bad to me.
The car running "really ruff in OL" is a real big bag of door ***** banging against my temple as well.
Can you elaborate? What software are you using? What fueling / airflow measurement methods are you employing? (OLMAF, OLSD, CLMAF, CLSD) What bar MAP sensor are you running? What type of WB02?
I'd like to help, just need more info.
The car running "really ruff in OL" is a real big bag of door ***** banging against my temple as well.
Can you elaborate? What software are you using? What fueling / airflow measurement methods are you employing? (OLMAF, OLSD, CLMAF, CLSD) What bar MAP sensor are you running? What type of WB02?
I'd like to help, just need more info.
05-03-2008, 09:59 AM
#7
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This car is runnign CLMAF, for now.
I haven't experienced the problem with this car first hand but based on his description (and the fact the issue didn't occur with OLMAF) it sounds like typical "cam surge". My Impala SS with LT4 HOT cam had this problem, and a cammed 2006 GTO I worked with had this problem. In both cases the car would shudder between 1500 and 2400 RPM during cruise conditions, almost like a misfire.
In both cases, I've spent a ton of time trying to tune this out to no avail (in CLMAF). Based on what I've read, the issue is that these "big" cams wreak havoc on the PCM's ability to manage the fuel mixture during closed loop operation. Due to the cam timing, the exhaust *looks* richer then it actually is (due to unburned fuel entering the exhaust), the PCM thinks it needs to lean the mixture out, starts subtracting fuel and the engine runs too lean, causing the shuddering.
In both the case of the Impala SS and the GTO, the employed solution was to convert it to OLMAF. In fact, the car this thread is about was running OLMAF for awhile, and it didn't have the surge when it was set up for OLMAF. OLMAF has its own set of challenges, though, which we'd like to avoid.
Currently, we are planning on enabling lean cruise on this car, and using it to enable open loop fueling during the surge conditions only. This should solve the surging problems while maintaining all of the other benefits of closed loop operation. I'd use the PE enable trick, but he's got a supercharger so this technique isn't safe to use.
I haven't experienced the problem with this car first hand but based on his description (and the fact the issue didn't occur with OLMAF) it sounds like typical "cam surge". My Impala SS with LT4 HOT cam had this problem, and a cammed 2006 GTO I worked with had this problem. In both cases the car would shudder between 1500 and 2400 RPM during cruise conditions, almost like a misfire.
In both cases, I've spent a ton of time trying to tune this out to no avail (in CLMAF). Based on what I've read, the issue is that these "big" cams wreak havoc on the PCM's ability to manage the fuel mixture during closed loop operation. Due to the cam timing, the exhaust *looks* richer then it actually is (due to unburned fuel entering the exhaust), the PCM thinks it needs to lean the mixture out, starts subtracting fuel and the engine runs too lean, causing the shuddering.
In both the case of the Impala SS and the GTO, the employed solution was to convert it to OLMAF. In fact, the car this thread is about was running OLMAF for awhile, and it didn't have the surge when it was set up for OLMAF. OLMAF has its own set of challenges, though, which we'd like to avoid.
Currently, we are planning on enabling lean cruise on this car, and using it to enable open loop fueling during the surge conditions only. This should solve the surging problems while maintaining all of the other benefits of closed loop operation. I'd use the PE enable trick, but he's got a supercharger so this technique isn't safe to use.
