LS Swap Runs Bad In Closed Loop
07-09-2024, 11:53 PM
#1
LS Swap Runs Bad In Closed Loop I have just completed an LS Swap (2001 5.3) into my 1981 El Camino. When in Open Loop at first startup the car runs great and drives like a champ. As soon as it hits closed loop it absolutely falls on its face. Immediately in the Short Term Fuel Trims the passenger side (Bank 2) shoots up to +51% almost instantly. While the driver side (Bank 1) goes down to -31% in the same speed as Bank 2. I will separate my multiple concerns below in hopefully an easy way to read and answer to.
I put new 02 sensors in it on the upstream, they are AC Delco. The rears are not in the exhaust but still plugged in. They should not be able to effect the performance at all. When taking out the old ones the passenger side was dark black while the driver was just a little black which is because the car wants +51% more fuel on the passenger side for some reason.
Full exhaust system with hi flow cats and mufflers, problem occurs with and without exhaust on the car.
My theory right now is that it is something wrong with the tune in the computer. If there was a major vacuum leak or non firing sparkplug/fuel injector, to my understanding the car should run bad in open loop aswell but in open loop it runs completely fine. Please correct me if i am wrong on this and if I should be checkin all the plugs and injectors.
NO CODES AT ALL
The engine, transmission and PCM were taken from one donor truck that ran good in open and closed loop. The computer was sent out to get the wiring harness re-done and removed a lot of the unnecessary things that connecter to the car itself. Now it acts as a standalone computer. I did give the guy some info like tire size and rear end ratio so he could adjust the tune. Unfortunately he does not do the harnesses anymore and was hard to reach even when he did. I believe there is a chance something could have been messed up while he was in there and want other peoples opinions about it.
I know a few guys around that could possibly help me look at the tune but I wanted to share this here and get some other eyes on it.
Let me know if there is any info I am missing that is crucial to diagnose this.
I put new 02 sensors in it on the upstream, they are AC Delco. The rears are not in the exhaust but still plugged in. They should not be able to effect the performance at all. When taking out the old ones the passenger side was dark black while the driver was just a little black which is because the car wants +51% more fuel on the passenger side for some reason.
Full exhaust system with hi flow cats and mufflers, problem occurs with and without exhaust on the car.
My theory right now is that it is something wrong with the tune in the computer. If there was a major vacuum leak or non firing sparkplug/fuel injector, to my understanding the car should run bad in open loop aswell but in open loop it runs completely fine. Please correct me if i am wrong on this and if I should be checkin all the plugs and injectors.
NO CODES AT ALL
The engine, transmission and PCM were taken from one donor truck that ran good in open and closed loop. The computer was sent out to get the wiring harness re-done and removed a lot of the unnecessary things that connecter to the car itself. Now it acts as a standalone computer. I did give the guy some info like tire size and rear end ratio so he could adjust the tune. Unfortunately he does not do the harnesses anymore and was hard to reach even when he did. I believe there is a chance something could have been messed up while he was in there and want other peoples opinions about it.
I know a few guys around that could possibly help me look at the tune but I wanted to share this here and get some other eyes on it.
Let me know if there is any info I am missing that is crucial to diagnose this.
Today, 12:23 PM
#3
I wonder if your front and rear sensors are wired correctly in your new harness?
I would unplug your rear sensors and make sure you get the proper codes for that "problem," which would partially confirm the wiring for the sensors. (i.e. If you get a code back for one front sensor and one back sensor, that would confirm a wiring problem.)
I would unplug your rear sensors and make sure you get the proper codes for that "problem," which would partially confirm the wiring for the sensors. (i.e. If you get a code back for one front sensor and one back sensor, that would confirm a wiring problem.)