Guys and Gals new to the forum so please bear with me, I recently purchased a 2006 Vert with Z-51 package, 6 speed, the problem is when I press the accelerator the throttle responses well but when I take my foot off the accelerater it does not throttle down. It will gradually throttle down after several seconds. Had my trusty Vette Mechanic look at it and he said everything was fine, any ideas as to what is causing this?

 

Vettes wind up faster than they wind down - careful if u're not used to.

 

Has the car been tuned? If the throttle follower or minimum idle air tables have been "adjusted", the "roll off" where the engine RPMs fall will be slowed. It is usually referred to as "cruise control" effect. You lift, and it takes it's sweet a$$ed time to slow down.

Elmer

 

Whoa... that could be an interesting problem!

Something sticking, peddle, etc.??

 

Yep, my 05 does the same thing. It's ok if you wind it up a little before shifting as it makes a smoother transition. It is worse when cold, better when warmed up.

 

Car has not been tuned, and accelerator is not sticking it just takes time for it to throttle down, I previously had a C-5 and throttle response was instant.

 

I've noticed the same thing, however, I noticed that if you are moving, then it throttles down quickly as it should. When its stopped and you rev the engine, it takes longer.

 

The throttle is completely fly-by-wire. No matter how abruptly you release the pedal, it won't allow the throttle plate to snap shut quickly. It may seem similar to an older car with a slightly sticky linkage. It definitely isn't instant.

You might compare to another C6 to confirm that yours isn't taking an extra-long time, but I suspect your car is normal.

 

Drove other Vette similiar to mine and there is a distinct and notable differance. I may add that the Tech who checked the car said that all fly by wire parameters were within spec. Thanks for all the responses but I'm still baffled.

 

Not sure whether your are referring to the rpms sometimes dropping to idle "normally" and sometimes only slowly returning to idle and/or seeming to slightly "hang up" for a second or so on the way back to idle (at ~1.5-2K +/- rpm).

If this is what you are describing, it's "normal," in the sense that it is programmed into the computer for emissions reasons -- in certain engine states, an instant drop to idle would be detrimental to emissions and/or equipment (like the cats), so the GM engineers program in an rpm drop delay to extend the drop and thereby keep EPA happy.

 

It's like a three second delay and then it starts to slowly drop. I drove other Vetts and this different. On both my C-4 and C-5 the throttle response was instant both ways

 

Sounds like it could be the throttle position sensor is going bad. Any codes from a Tech II?

 

I've observed the same thing with my '08 'vert -- emissions issue.

I do patent work in the automotive emissions field -- you'd be amazed at hte complexity of some of the control schemes for shifting fuel and air mixtures between lean, rich, and stoichimetric (as well as other during- and post-combustion injection tricks) for the purposes of precisely controlling the amount of exhaust products build up on, and purged from, the downstream emissions absorption and conversion devices. Let off the throttle when one of these processes is in progress, or even just let off in a way that will result in insufficient amounts of a component being present at the right time (e.g, insufficient unburned hydrocarbons, excess oxygen), and you can screw up the balance and get a short-term undesired emission exceedance. Delay of drop to idle rpm eliminates this issue to maintain the EPA certification compliance.

 

have you taken your tech out for back to back drives in the two different presenting C6s? if not, that's one way to demonstrate the difference. and if he is actually a Chevy dealer tech, maybe a suggestion would be for him to reprogram the computer in your car (or swtich out the throttle position sensor) to see if this helps. if he does it in his position, it won't be counted as a "tune" per se but an authorized repair procedure. anyone else doing it will affect (potentially) your warranty going forward on certain parts of your powertrain.

 

A full 3 second delay in throttle closing is not normal, 3 seconds is a long time. do you really mean a true 3 seconds, or was that just a very rough guesstimate?

I also have a 2006 Z51 6-speed manual. I would definitely describe my throttle closing behavior as having a "delay" and I don't like it but have learned to deal with it.

When the engine is cold there is little throttle closing delay. In some cases, when cold, especially at lower rpm, the throttle drops so fast that I cannot shift fast enough to rev match. Delay increases once the engine is hot. Delay is also greater at higher rpms. Like, if I shift from 2 to 3 at 2500 rpm, the delay is there but not too bad, but if I make the same shift instead at 3500 rpm or higher, the delay will be noticeably greater. It almost appears that the throttle is "stuck" open right after you release it, then starts dropping maybe a second later (or probably less than a full second, but in a shift situation, even three-quarters of a second is a long time).

This somewhat inconsistent throttle return behavior has proven to be a bit annoying, especially for those with a "quiet" stock exhaust like me. I literately have to glance at the tach in many cases in order to perform a perfect rev-matched shift because I can't really hear the engine, especially with the top off. And since the throttle return behavior is inconsistent, it's impossible to "memorize" it, you never quite know if you're gonna get the "big delay" or just the "medium delay", etc, and needless to say this is all happening very fast while you're burning through the twisties at 75mph with most of your attention on the road, it's not like you can sit back and study what's going on.

I once spoke to a tuner about having the car tuned so the throttle return response would be faster and consistent. The general answer was that the delay in the throttle closing has something to do with keeping the cats from overheating and by quickening the return the cats could be harmed. It was also suggested that it might be hard or impossible to tune the car so that the throttle would return fast and consistent at all times, at least not without causing issues with other aspects of tuning / emissions etc to the point where it would not be worth even trying.

It was hard at first, but I've now gotten used to quickly glancing at the tach when upshifting to observe roughly what kind of delay is going to happen with the throttle return so that I can make smooth rev-matched shifts. I've considered and still considering getting a louder exhaust so I can just use my ears to monitor rpms, but when I'm cruising on the highway on a long trip I much enjoy how quiet the car is and I'd hate to toss that aspect out the window.

All in all though, you do get used to the overall behavior of the car and at that point none of this is really a problem. I've driven other cars that were way worse in this regard.

 

Lots of great suggestion which I really appreciate. It really is a three second delay when the engine is cold and improves as it heats up and with Corsa Extremes it's easy to tell. Will try a different Tech along with the numerous helpful suggestions, Thanks!!!!! SEVETGO

 

I have to out and try my pedal again, David. I don't recall this happening in mine, but maybe I just got used to it.

 

try to find the complete service history of this car. the reason for this is if someone changed the flywheel to a diffrent weight. if your car is a 6-spd manual trans. if the previous owner had a clutch installed, they may have also installed a lighter flywheel thinking it would give it a performance edge. i went through this with someone with the same problem. the flywheel was'nt stock, so the rpms would not come down normally. we changed to the correct flywheel, and it worked fine. hope this may help. cranky

 

Todays car engines have a mind of their own; don't expect them to respond the same as when the accelerator pedal was connected by linkage directly to a throttle plate. In case you haven't noticed, their is a distict pause in everything you command the car to do while the computers check the status on a whole host of items before it allows the command to be executed. You push the "start" button and the computer thinks about it a while before actually signaling the starter to engage and start the engine.