I've noticed in my T/A that when i let off the throttle, the engine doesn't respond very quickly. Like if i just rev the motor, it'll still rev up a little after i let off the throttle. Similarly, if i'm hard on the gas, and then let off and put the clutch in, the engine will actually rev up a bit. Is this a common thing with LS1s that I should just get used to or is there something I should adjust to fix it?

My gut tells me to check/adjust the TPS, which i could do on my old MX-6 with a paperclip and a phillips head driver, but with OBD-II and the LS1, I'm lost.

 

Its tuned that way.

 

both my 96 and my 99 have done the same thing....

always attributed it to lag in the throttle and computer.

 

Is there a reason for it to behave that way? Or is it something that can be reprogrammed with a tune? It's not really a huge deal, but it's a little unsettling sometimes. When I let off the gas, i want the thing to stop accelerating right then and there, not keep going for a little bit. Heh.

 

check to make sure the sping on your TB is in good shape. could be it's not pulling the blades closed fast enough.

also have you used any kind of carb cleaner or top end cleaner recently? i know years ago i cleaned my TPI throttle body with some carb cleaner to get all the buildup off...ended up dissolving all the lubriction. letting off the gas at 50mph+ would act like cruise control and hold a speed. i would have to brake HARD to get it to a stop since the blades were stuck open. little oil and it cured it right up

 

The tb response when you let off is under the PCM's control somewhat. There's a table in everyone's tune called "Throttle Follower" that actually keeps the throttle body open (different amounts at different speeds). The IAC motor is what physically moves the blade. If you have a friend with an IAC motor in good condition, I'd see about swapping/borrowing his for a test drive. If it feels better/different, it could be time for a new IAC motor. While you have the intake apart, check the spring/lubrication of the tb. The only other place I could think of a potential problem is either the actual cable is binding up somewhere or your gas pedal is sticking to the carpet somehow.

 

I've checked out the cable and throttle linkage and there's no binding or rubbing anywhere. It all moves freely. The car has always been this way, so it's not anything new really. It's just different. I'll see if I can dig up someone willing to swap IAC's.

I think mostly what I'm looking for is the possible reasoning for making it do that. The closest thing I can think is for emissions, ensuring that when you get off the gas quickly, you don't get a rich condition for a bit.

Along with that, is there a way to change that with a PCM tune?

 

That's my understanding of the throttle hold . . . It prevents the dumping of HC's (from a rich mixture) which would result if the throttle would close right away.

 

My car would do those things if I had my front defroster on. I know that sounds weird but I've tested it several times and it would surge when I put the clutch in until I either gave it awhile to calm down or if I clicked the HVAC off of defrost. It would return to normal right away. I always attributed this to an emissions thing too since the compressor is running with the front defroster.

 

Its like that for a reason.