Hey guys! Still trying to get my car dialed in. During a data logging session tonight my car was in open loop for quite a while starting out, well into 185+ degrees. It finally went into closed loop but whenever I came to a stop it would shift back to open loop. Is this normal? The car has a 180 thermostat and runs around 190-192 for the most part with the temps we have right now. Is the entrance into closed loop adjustable by programing or is it a default factory setting? This is a 93 lt1 with the factory ecm.
Log to see what the O2 sensors are showing. If the PCM doesn't think they are sufficiently warmed up it's going to go open loop. If you're still running the original O2 sensors, replace them. They really aren't terribly accurate after 50,000 miles and continue to get worse as they put on miles. I bet it's running rich, right?
It is running rich for sure, fouls plugs on bank one. I replaced the o2 sensors last fall, they have maybe 2-300 miles on them. I believe I put ac Delco in. Reading the data log the o2 sensors do move throughout their range quickly. In open loop they just poke around, but I think that’s normal?
Ok. After evaluating my data log the tuner said the fuel trims are adding fuel and in some cases as much fuel as they possibly can. He tells me that can indicate several possible issues. A true lean condition An exhaust leak A misfire condition Can the computer control fuel for each cylinder bank individually or is the fueling the same from side to side? I was fouling plugs on the bank one side last year. I’m still wondering why just that side was fouling. Maybe misfire on bank one? or vacuum leak on bank 2? If there was a leak into bank 2 would the computer compensate by richening both banks?
The tuner also told me if he were to make changes to the data he would add fuel. Also mentioned I could add heated o2 sensors to stop the back and forth from open and closed loop. And my tps is sticking here and there causing some minor idle down issues. Unfortunately I am only able to email with him because I don’t have cell service where I am working this week.
93 is set in speed density and shouldn't have open and closed loops that I'm aware of. I have not done much on 93's though or eeprom for that matter so I could be wrong.
Sorry I didn't get back sooner to this thread, work is too busy these days. There isn't individual cylinder fuel changes, it's one bank or the other. O2's should switch up and down, but not too fast. Every second or so, or slower is normal. I'd get a can of maf cleaner, and spray around various areas. If the idle changes, you have a vacuum leak. Does the car have headers? That can cause the O2 sensors to not get enough heat.
The car does have long tube headers and the o2 sensors are farther from the engine than they used to be. Hopefully I can do some diagnostics this weekend if I get time, Spring yard cleanup is is in full swing at the moment.
