Ok, been trying to figure this out for about a year now. My car runs real real sluggish after it goes into closed loop. Mainly on highway trips though. The car has extrememely poor acceleration only after a long highway trip. Feels like some kind of heat soak? Ok, it runs awesome in open loop. I mean really good. Now this is the thing. My car started doing this only after it was driven last year for a 50 mile trip with the radiator cap loose and the radiator empty. I did manage to add water ,but only after we got off of the expressway. This is because the cool air at highway speeds showed my temp gauge at 150, that is where it should be at 150 or lower all the time. Now, it went up to 250 after i finally came to my first stop off of the freeway and that is when i added water finally. SO, ever since then my car has been feeling a little slower, and ONLY after a long highway trip. So, it is basically like this. I am going down the highway after a LONG trip and then come to my first stop at a light. The car bogs, feels like something is clogged and has really really really poor off the line acceleration all of a sudden. After the engine cools down it runs awesome again! until it heats up or after about 30 min of continuous driving, then it runs like total **** again. So, is something expanding due to heat ? I need opinions on this please. I may have a bent valve? I dont think it is a head gasket. Oh, and the car has new fuel press regulator, dist cap, rotor, fuel injectors, no codes, no clogged converters, fuel injection cleaner ran on a regular basis, oil always changed every 3000 miles.

 

Could use a bit more information. There are a few differences between how the system works in open and closed loop mode. From a input sensor perspective the 02 sensor is used or ignored many of the emissions controls also are either used or not depending on weather its in open or closed loop. So seeing as how according your cars info you have a vette TPI set up swapped in I'm curious if you've retained all emissions controls or other mods ect. The other thing that confuses me is you say it runs bad when it goes into closed loop. Ideally the car should just about always be in closed loop except for when first starting so how did you come to the conclusion that the car is actually dropping out of closed loop operation when it runs good?

 

Hey man, I figured it out finally. My timing was set at 0 degrees . Been that way ever since I bought the car. Just set it to 6 degrees btdc. Never been faster!