Lazy throttle return problem.
#1
09-13-2006, 03:37 PM
Lazy throttle return problem.
When lifting off the throttle while cruising (about 60 mph), the throttle takes forever to return to a slower speed. I can place trans in neutral while lifting of the accelerator and the tack very slowly begins to a rpm drop off. It mite take 10 seconds to get back to idle RPM. Any suggestions what might be the problem or a cure?? Thank you for any input. 
#3
09-13-2006, 09:01 PM
RE: Lazy throttle return problem.
A quick question. Is the throttle pedal lazy, too? In other words, when you lift off, does it stay down and only gradually rise? If so, the spring inside the reostate (drive by wire) assembly has broken - about $225 in parts and less than 30 minutes to repair.
If this is not the problem, it could be a sticking throttle plate, although you ought to get an ECM code on that. Does you car report any codes when you query it? It could be the stepper motor, but it is unusual for them to fail "slow" in only one direction (if it took ten seconds when you floored the throttle, too, I'd think this was the case).
If this is not the problem, it could be a sticking throttle plate, although you ought to get an ECM code on that. Does you car report any codes when you query it? It could be the stepper motor, but it is unusual for them to fail "slow" in only one direction (if it took ten seconds when you floored the throttle, too, I'd think this was the case).
#4
09-14-2006, 09:01 AM
RE: Lazy throttle return problem.
Bill - I got your e-mail and sent the below in reply but your spam filter rejected it, so here it is:
Given it does not do this "trick" in neutral, as not there is a reason that the ECM (engine control module) is holding the throttle open on slow down. I dfoubt this is a mechanical ( sticky throttle or plate) issue, or a problem with the stepper motor.
Be prepared for your shop or dealer to spend $250 or so of your money replacing the throttle pedal - they nearly always do this first and there is a slight possibility this will fix it (about 5% is all, I think).
If it were my car I would take it to a local "tuner guru" and not the dealer or a mechanics shop -- someone with LS1 edit who knows what he is doing (lots of people have the former, few can claim the latter). Here in central NC, its Jeff Creech at Carolina Auto Masters, but there are others in other areas. A good sign to look for is: do they have a dyno and do they tune and re-program ECMs for modified corvettes and camaros?
Here is all I know. The ECM is programmed to let the throttle close slowly under some conditions, generally when the driver has let his foot off the throttle while the car is still moving and in gear (the reasons make sense but are beyond what I can cover here), other times for emissions reasons. Either way, it sounds to me like your car is overreacting to this. My car (heavily modified) used to over-react too and sometimes hold RPM at around 1500 even after it came to a full stop, etc. This feature can be re-programmed, so it can be fixed (I think the ECM can even be told to not do this at all, but you would not like how the car drives - a bit of this feature does make it behave more intuitively).
If your car has been even lightly modified (headers, new intake, or more) this could be the problem. What would concern me is why this just recently started happening. I would ask the shop to scan all codes, check all sensors, etc. If it is stock then something changed (broke?). Offhand, I would suspect O2 sensors or something, except you ought to get a check engine light on those, and you did not report that.
And, it is worth asking this lame question: have you switched gasoline brands or grades lately? My 'vette does not like one particular station'sgas. Don't know why. I just don't run it on that.
Given it does not do this "trick" in neutral, as not there is a reason that the ECM (engine control module) is holding the throttle open on slow down. I dfoubt this is a mechanical ( sticky throttle or plate) issue, or a problem with the stepper motor.
Be prepared for your shop or dealer to spend $250 or so of your money replacing the throttle pedal - they nearly always do this first and there is a slight possibility this will fix it (about 5% is all, I think).
If it were my car I would take it to a local "tuner guru" and not the dealer or a mechanics shop -- someone with LS1 edit who knows what he is doing (lots of people have the former, few can claim the latter). Here in central NC, its Jeff Creech at Carolina Auto Masters, but there are others in other areas. A good sign to look for is: do they have a dyno and do they tune and re-program ECMs for modified corvettes and camaros?
Here is all I know. The ECM is programmed to let the throttle close slowly under some conditions, generally when the driver has let his foot off the throttle while the car is still moving and in gear (the reasons make sense but are beyond what I can cover here), other times for emissions reasons. Either way, it sounds to me like your car is overreacting to this. My car (heavily modified) used to over-react too and sometimes hold RPM at around 1500 even after it came to a full stop, etc. This feature can be re-programmed, so it can be fixed (I think the ECM can even be told to not do this at all, but you would not like how the car drives - a bit of this feature does make it behave more intuitively).
If your car has been even lightly modified (headers, new intake, or more) this could be the problem. What would concern me is why this just recently started happening. I would ask the shop to scan all codes, check all sensors, etc. If it is stock then something changed (broke?). Offhand, I would suspect O2 sensors or something, except you ought to get a check engine light on those, and you did not report that.
And, it is worth asking this lame question: have you switched gasoline brands or grades lately? My 'vette does not like one particular station'sgas. Don't know why. I just don't run it on that.
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