LS swap driveability issues...
Thread Starter
Registered User
Joined: Dec 2014
Posts: 16
Likes: 0
Wow lot of random info in here.
Lets get to the heart of the matter.
You are running currently in SD mode since there is no MAF.
Speed Density requires two things (actually several things but for simplicity here) it needs to know the Manifold Absolute Pressure (MAP) and it needs to know the Intake Air Temp (IAT). It uses this information combined with a few other things to figure out fueling when running in SD mode.
You have no IAT connected. So the PCM is getting no reading from the IAT and when this happens it assumes that the car is in a cold environment and defaults to the bottom of the IAT fueling enrichment table for fueling requirements. I don't have my HPT in front of me to look but I know from memory it's well bellow -32 as I recall. This means your car will fuel based of this table which in cold environments makes the car run very rich.
So its able to idle but doing so in a rich afr most likely. Light throttle transitions work as it doesn't call in any other enrichment tables but as soon as you given it any real throttle it calls in different enrichment tables which only continue to add even more fuel. Your flooding the engine to a very rich Afr and it's dying out because of that.
That would be my guess based on the info your giving us.
SD mode needs the MAP sensor and the IAT sensor to function. With out the IAT the PCM can' not figure out the density of the air as air molecules get more dense the colder they are ... and less dense the warmer they are so for proper fueling it must have an idea what the temp of the air coming in is. It makes a big difference. And on the stock o/s if it does not see an IAT reading it assumes the coldest setting possible.
Wire in the IAT it' is a necessity for SD mode.
Lets get to the heart of the matter.
You are running currently in SD mode since there is no MAF.
Speed Density requires two things (actually several things but for simplicity here) it needs to know the Manifold Absolute Pressure (MAP) and it needs to know the Intake Air Temp (IAT). It uses this information combined with a few other things to figure out fueling when running in SD mode.
You have no IAT connected. So the PCM is getting no reading from the IAT and when this happens it assumes that the car is in a cold environment and defaults to the bottom of the IAT fueling enrichment table for fueling requirements. I don't have my HPT in front of me to look but I know from memory it's well bellow -32 as I recall. This means your car will fuel based of this table which in cold environments makes the car run very rich.
So its able to idle but doing so in a rich afr most likely. Light throttle transitions work as it doesn't call in any other enrichment tables but as soon as you given it any real throttle it calls in different enrichment tables which only continue to add even more fuel. Your flooding the engine to a very rich Afr and it's dying out because of that.
That would be my guess based on the info your giving us.
SD mode needs the MAP sensor and the IAT sensor to function. With out the IAT the PCM can' not figure out the density of the air as air molecules get more dense the colder they are ... and less dense the warmer they are so for proper fueling it must have an idea what the temp of the air coming in is. It makes a big difference. And on the stock o/s if it does not see an IAT reading it assumes the coldest setting possible.
Wire in the IAT it' is a necessity for SD mode.
Thread Starter
Registered User
Joined: Dec 2014
Posts: 16
Likes: 0
Yeah the trans am is the same way. Using parts from extra trans am I stuff I had, I wired up mass and IAT. Runs like a champ now. Thanks
