Why is my motor running lean
Thread Starter
Teching In
Joined: Sep 2006
Posts: 22
Likes: 0
Why is my motor running lean Here is the background. I put a forged LS6, with a brute speed cam, LS6 intake, patriot 5.3 stage 3 heads, 60 lbs injectors and a P1SC into my 99 Trans AM. I had ordered a mail order tune to get my car started. The car would start right up but it would not idle unless I would tip into the pedal and bring the TPS up to 9% where the car would idle at 900 rpm and 14.5:1 AFR.
Today I pulled the the throttle body off and adjusted the set screw to allow more airflow at idle. I pulled off the IAT sensor, TPS sensor and the harness for the IAC motor. I then cycled the key to reset my TPS sensor to 0. I then plugged everything back. I tried to start my car and it barely stayed alive, my wideband was reading 18:1 and it was misfiring. I put everything back the way it was when I had it running, reset the TPS sensor again (it would read 0 in HP Tuners) and then tried again. I could barely get the engine started and it ran super lean then died.
I checked my fuel pressure which was 60 psi and I know the tune worked before. Does anyone have any ideas of what could be the problem? Think it might be related to the TPS?
Today I pulled the the throttle body off and adjusted the set screw to allow more airflow at idle. I pulled off the IAT sensor, TPS sensor and the harness for the IAC motor. I then cycled the key to reset my TPS sensor to 0. I then plugged everything back. I tried to start my car and it barely stayed alive, my wideband was reading 18:1 and it was misfiring. I put everything back the way it was when I had it running, reset the TPS sensor again (it would read 0 in HP Tuners) and then tried again. I could barely get the engine started and it ran super lean then died.
I checked my fuel pressure which was 60 psi and I know the tune worked before. Does anyone have any ideas of what could be the problem? Think it might be related to the TPS?
Your mail-order tune is not properly calibrated for your engine. You should not have to trick your PCM into idling by messing with the TB set screw. Back out all the changes and put it back to stock, add ~5% to your idle running airflow, VE, and MAF tables to get it in the ballpark, and tune from there.
LS1TECH Sponsor
Joined: Jun 2002
Posts: 636
Likes: 1
From: Cumming, GA
Here is the background. I put a forged LS6, with a brute speed cam, LS6 intake, patriot 5.3 stage 3 heads, 60 lbs injectors and a P1SC into my 99 Trans AM. I had ordered a mail order tune to get my car started. The car would start right up but it would not idle unless I would tip into the pedal and bring the TPS up to 9% where the car would idle at 900 rpm and 14.5:1 AFR.
Today I pulled the the throttle body off and adjusted the set screw to allow more airflow at idle. I pulled off the IAT sensor, TPS sensor and the harness for the IAC motor. I then cycled the key to reset my TPS sensor to 0. I then plugged everything back. I tried to start my car and it barely stayed alive, my wideband was reading 18:1 and it was misfiring. I put everything back the way it was when I had it running, reset the TPS sensor again (it would read 0 in HP Tuners) and then tried again. I could barely get the engine started and it ran super lean then died.
I checked my fuel pressure which was 60 psi and I know the tune worked before. Does anyone have any ideas of what could be the problem? Think it might be related to the TPS?
Today I pulled the the throttle body off and adjusted the set screw to allow more airflow at idle. I pulled off the IAT sensor, TPS sensor and the harness for the IAC motor. I then cycled the key to reset my TPS sensor to 0. I then plugged everything back. I tried to start my car and it barely stayed alive, my wideband was reading 18:1 and it was misfiring. I put everything back the way it was when I had it running, reset the TPS sensor again (it would read 0 in HP Tuners) and then tried again. I could barely get the engine started and it ran super lean then died.
I checked my fuel pressure which was 60 psi and I know the tune worked before. Does anyone have any ideas of what could be the problem? Think it might be related to the TPS?
Thread Starter
Teching In
Joined: Sep 2006
Posts: 22
Likes: 0
It could have nothing to do with the TPS, it was just something I was adjusting before the car ran like crap.
