CAR STUTTERS AT HIGH RPM.. Why?

qws2000

Active Member
Joined
Jan 12, 2012
My car starts to stutter when it pulls into the high rpm's. I have a powerlogger scan master but cant get it to print... But here are some of the numbers im getting.. If anyone can can help, thank you
rpm; 5775
ECM AFR; 7.3:1
MAF; 256.0 G/S
TPS; 3.64 V
WASTEGATE; 89.8%
IAC;79 Cts
WB AFR; 10.69:1
MAP; 278.90 KPA
INTAKE AIR; 56.5 Deg
Ign Volts: 14.5 V
Boost: 25.8 Psi
02; 0.823 V
Advance; 24.7 Deg
Injector Pw; 13.32 mS
Injector Duty; 63.3%
I really need some help here.. The car has about 1200 miles on a total rebuilt motor and tranny, all new parts
 
You are flooding the motor at an AFR of 7.3 to 1. More than likely the stuttering you are talking about is so much fuel being added between the gas and alky that you are blowing out the spark. You should be shooting for an AFR of 10.5 to 1., 11 to 1 is ok with less timing. And back the timing down to 21 degrees, 24 is great for a dead on tune but if its not then you can pop a head gasket easily.
You have good voltage to everything, that is a plus. You dont list whether you have a single or double pump set up. If its a single you are fine, if its a double that would explain a couple of things. If you do have a double pumper, turn it off. You only need one good in tank pump, the alky takes care of the rest.

Back the boost off to 10 psi, i know it will feel slow right?, run at 10 psi and see what it does. If it is running well at that level then turn it up to 15, then 20 and so on. 26 psi with 25 degrees of timing is a bunch of power but you have to make sure it is tuned correctly.

Rules of thumb. Set the alky turn on point at 8 psi and leave it alone. Turn the gain knob to 6. Turn the timing down to 20 degrees so you dont blow it up. Ask me how I know. ;)

If you have a double pumper, turn off the second pump it is now overkill. What happens is the second pump kicks on at a set boost level and you double the volume of fuel going to the injectors. The ECM can only take out so much to try and compensate. It wont be enough. Add twice the amount of fuel and the alky on top and you get a pig rich motor that runs like crap and you cant figure out why.

Your TT chip can be changed up easily, grab the instruction sheet that came with it. If you dont have that go to Eric's website. Instructions are listed there. I am assuming you gave him all the info he needed to burn the chip correctly for your combo.

Hell I run mine at 21 psi and 20 degrees timing and there is not much that keeps up with me. Yours should be faster.

Good luck.
 
You are flooding the motor at an AFR of 7.3 to 1. More than likely the stuttering you are talking about is so much fuel being added between the gas and alky that you are blowing out the spark. You should be shooting for an AFR of 10.5 to 1., 11 to 1 is ok with less timing. And back the timing down to 21 degrees, 24 is great for a dead on tune but if its not then you can pop a head gasket easily.
You have good voltage to everything, that is a plus. You dont list whether you have a single or double pump set up. If its a single you are fine, if its a double that would explain a couple of things. If you do have a double pumper, turn it off. You only need one good in tank pump, the alky takes care of the rest.

Back the boost off to 10 psi, i know it will feel slow right?, run at 10 psi and see what it does. If it is running well at that level then turn it up to 15, then 20 and so on. 26 psi with 25 degrees of timing is a bunch of power but you have to make sure it is tuned correctly.

Rules of thumb. Set the alky turn on point at 8 psi and leave it alone. Turn the gain knob to 6. Turn the timing down to 20 degrees so you dont blow it up. Ask me how I know. ;)

If you have a double pumper, turn off the second pump it is now overkill. What happens is the second pump kicks on at a set boost level and you double the volume of fuel going to the injectors. The ECM can only take out so much to try and compensate. It wont be enough. Add twice the amount of fuel and the alky on top and you get a pig rich motor that runs like crap and you cant figure out why.

Your TT chip can be changed up easily, grab the instruction sheet that came with it. If you dont have that go to Eric's website. Instructions are listed there. I am assuming you gave him all the info he needed to burn the chip correctly for your combo.

Hell I run mine at 21 psi and 20 degrees timing and there is not much that keeps up with me. Yours should be faster.

Good luck.

ECM AFR is not the true AFR it's commanded. His true AFR is 10.69
 
reggie..... Thanks for all the time you spent tryn to help me... I do hav a Double Pumper, the chip is set for 100/25-28psi, and alky, it is set at 6, I thought the AFR is 10.69????
 
I think Aminga is right. I did not catch that looking through your numbers.

I use a FAST system but I dont know if 10.69 AFR equates to the O2 voltage reading .863, you may still be rich. If you are running both pumps and the alky you are definitely running rich. If you decide to turn off the second pump make certain you turn the boost down to 10 psi and work your way back up. I dont want you to blow a head gasket.

I would also have a look at your spark plug gap on the plugs. You can blow out the spark at higher boost levels, the fix is to set the gap at .025.

Hope that helps.
 
reg.. I just noticed the powerlogger stated at that time the spark dial was reading 24.7 deg..... Does that sound right?? thanks AL
 
I would back it down to 21 degrees and leave it there. Without having the fuel tables dialed in just right I would play it safe. After the AF ratios are correct you can see if more timing helps or not. Small steps will get your tune just right.
 
not to hijack but what exactly is a free air calibration for a wideband?

Innovate LC1 widebands have to be periodically calibrated using free air as a reference gas. AFAIK only the innovate widebands require this.
 
WE2,.. Im not sure if that is a bad reading....Kid,..The coil pack is AC Delco (This my 2nd one) and wires MSD 8.5mm super conductor and plugs not sure... Chuck; I am new to GN scene and not a motor head guy, but love these car's and eager to learn, with that said I have no idea what you are asking.... I have mor numbers if someone thinks it will help.....
 
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