My car doesn't have cruise control...but it acts like it does.
Dear Car Talk | Jul 01, 1997
Dear Tom and Ray:
just discovered it has a feature I don't want: virtual cruise control! It
doesn't have cruise control, but it sometimes acts like it does. Sometimes when
I take my foot off the gas pedal, the car just keeps going. I can make it stop
by downshifting, and it only happens in very cold weather. It only occurs in
third or fourth gear on an open road after I've been driving for a while
(although that could be coincidence because it's only happened a couple of
times).
I brought it into my mechanic, but I couldn't get it to happen in front of him
(of course). He checked the cables and said they look OK. Any other suggestions?
-- Mary
RAY: Virtual cruise control, eh? I guess that means my brother's '63 Dart has
"virtual theft deterrent." Some mornings, it acts like it has a sophisticated
theft-deterrent system and refuses to start!
TOM: I think you've either got a sticking throttle or a problem with the idle
air control, Mary.
RAY: The throttle could be sticking in a number of places. It could be hanging
up right at the gas pedal, or somewhere in between the pedal and the throttle
body. You can check that by reaching your toe around behind the pedal next time
this happens, and see if you can "pull" the pedal toward you and stop the
acceleration.
TOM: Or, since it's only a cold-weather phenomenon, ice could be building up in
the throttle body and causing the throttle to stick in the open position.
RAY: If it's not something mechanical like that, it could be an electronic
problem. This car has an idle air control (IAC), which allows the computer to
increase the engine idle speed by sending more air into the cylinders.
TOM: The IAC itself could be faulty, or more likely something else is wrong
(like too rich a mixture), and the computer is telling the IAC to send in more
air because of that other problem.
RAY: So if your mechanic can't find evidence of a sticky throttle, ask him to
"scan," the engine and look for an IAC problem, or another problem which is
responsible for boosting the IAC.
TOM: And don't forget (and this is for everybody), if you ever find yourself in
a dangerous situation where the car is accelerating and you don't want it to
(where you have a "runaway car" or "unintended acceleration"), here's the proper
procedure to follow: First, depress the clutch and shift into Neutral (or just
shift into Neutral if you have an automatic transmission). The engine may be
revving like crazy at this point, but ignore it. Since it's revving in Neutral,
the car won't be accelerating anymore, and you should be able to slow down.
RAY: But don't shut off the engine yet. Without the engine running, you'll lose
your power steering and power brakes. Once you've safely pulled over and stopped
the car, then you can turn off the engine. At that point, you've avoided a
tragedy and you're ready for the final step in this procedure: thanking your
lucky stars and cursing out the manufacturer.
What's one secret of financial success? Driving a used car! Read How to Buy a
Used Car: Things Detroit and Tokyo Don't Want You to Know. You can order it by
sending $3 and a stamped (55 cents), self-addressed, No.10 envelope to Used Car,
PO Box 6420, Riverton, NJ 08077-6420.
just discovered it has a feature I don't want: virtual cruise control! It
doesn't have cruise control, but it sometimes acts like it does. Sometimes when
I take my foot off the gas pedal, the car just keeps going. I can make it stop
by downshifting, and it only happens in very cold weather. It only occurs in
third or fourth gear on an open road after I've been driving for a while
(although that could be coincidence because it's only happened a couple of
times).
I brought it into my mechanic, but I couldn't get it to happen in front of him
(of course). He checked the cables and said they look OK. Any other suggestions?
-- Mary
RAY: Virtual cruise control, eh? I guess that means my brother's '63 Dart has
"virtual theft deterrent." Some mornings, it acts like it has a sophisticated
theft-deterrent system and refuses to start!
TOM: I think you've either got a sticking throttle or a problem with the idle
air control, Mary.
RAY: The throttle could be sticking in a number of places. It could be hanging
up right at the gas pedal, or somewhere in between the pedal and the throttle
body. You can check that by reaching your toe around behind the pedal next time
this happens, and see if you can "pull" the pedal toward you and stop the
acceleration.
TOM: Or, since it's only a cold-weather phenomenon, ice could be building up in
the throttle body and causing the throttle to stick in the open position.
RAY: If it's not something mechanical like that, it could be an electronic
problem. This car has an idle air control (IAC), which allows the computer to
increase the engine idle speed by sending more air into the cylinders.
TOM: The IAC itself could be faulty, or more likely something else is wrong
(like too rich a mixture), and the computer is telling the IAC to send in more
air because of that other problem.
RAY: So if your mechanic can't find evidence of a sticky throttle, ask him to
"scan," the engine and look for an IAC problem, or another problem which is
responsible for boosting the IAC.
TOM: And don't forget (and this is for everybody), if you ever find yourself in
a dangerous situation where the car is accelerating and you don't want it to
(where you have a "runaway car" or "unintended acceleration"), here's the proper
procedure to follow: First, depress the clutch and shift into Neutral (or just
shift into Neutral if you have an automatic transmission). The engine may be
revving like crazy at this point, but ignore it. Since it's revving in Neutral,
the car won't be accelerating anymore, and you should be able to slow down.
RAY: But don't shut off the engine yet. Without the engine running, you'll lose
your power steering and power brakes. Once you've safely pulled over and stopped
the car, then you can turn off the engine. At that point, you've avoided a
tragedy and you're ready for the final step in this procedure: thanking your
lucky stars and cursing out the manufacturer.
What's one secret of financial success? Driving a used car! Read How to Buy a
Used Car: Things Detroit and Tokyo Don't Want You to Know. You can order it by
sending $3 and a stamped (55 cents), self-addressed, No.10 envelope to Used Car,
PO Box 6420, Riverton, NJ 08077-6420.
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