Turning off your car at 55 mph


#41

See we have lots of OMG alarmists here. It is no big deal.

Think about it, engines can say - run out of gas. What happens then? Well - you slow down and stop, all without the world ending (unlike! the! thoughts! of! the! first! poster!) :smiley: Amazing the manufacturers thought about that possibility eh?

Transmission: Automatic, semi-manual, or stick manual?
Stick - no problem at all.
For the other two - if won’t harm anything if you just turn it off and not back on.

Steering wheel lock:
Q: Is there another position until it locks? If so, again no problem.

Brakes:
You should have 1-2 pumps of vacuum assisted brakes (you always have brakes - just have to push harder). Maybe more if the throttle body closes (DBW) or you keep your foot off the gas peddle.

Power steering:
Electric or hydraulic assist - yes that will go away (no big deal on a straight road). You can still turn, just more work.

Engine:
No problem. The engine moving without being “on” is a normal state that happens every time you let off the gas with the gear engaged (no fuel is injected).

Self experience - I’ve done this countless times while tuning the car with the laptop. If you push the parameters just a little too far, you go into limp mode (very limited power). The only way to clear it is to turn the engine off and back on.

No big deal - on a manual where the steering does not lock. Just turn it off, wait a second, and turn the ignition back on (not to start). The engine is already turning, it just fires up and goes on…

I also routinely coast about 75 feet into my parking spot at work with the engine off. Guess that’s my part on being green. :smiley:


#42

I do this often when road testing a vehicle to determine noises or other problems.

Don’t turn the key in lock position.Put transmission in neutral before turning off key.

Don’t attempt this unless you are experienced driver who can handle no power.


#43

I said engine off/stalled, not key turned off. I agree that if you turn the key off, the transmission will stop turning the engine.


#44

I did that once (left switch “on”) on a long trip that included lots of long hills on the interstate, with more down than up. Got 47 mpg for the trip when my normal average was 34.


#45

No, it can’t be bump started. You couldn’t get the transmission in gear and the converter locked without the hydraulic pump already running. In the case of a stall on the highway, the pump would already be turning. Since there was already pressure there, then the hydraulics stay engaged and running. For a bump start, there wouldn’t be any pressure to begin with, so no way to get things started.

Yes, there would still be engine braking function, because turning the engine is a load on the transmission. There would also still be vacuum for power brakes since the engine would be turning and pumping air.

If you want to test this, you can if your car has an fuel pump inertia cut off switch. Just tap the switch with a hammer while at speed. It will cut off fuel to the engine and you can see what happens.


#46

Question. If the converter is locked via the pump then this means a bump start should be possible as it should be locked to the flexplate which is bolted to the converter???

Since I don’t normally get into something like this I’m trying to remember any engine braking being involved with the engine off/key in the RUN position.
I’ve done this a number of times on the open road while fishing around for an answer to a problem on various cars and I don’t remember any engine braking occurring.

I’ll run my Lincoln up to about 60 or so tomorrow, kill the engine, and turn the key back to RUN and see what happens.


#47

The AT will indeed “reverse drive” the engine…and it doesn’t even have to be a terribly “modern” car.

Tried it last night in my '88 Dakota. Once at 30MPH (in 2nd gear) and at 40MPH (in “D”…i.e. 3rd).

Both times, the engine remained turning. Flooring the throttle had no effect (other than to make the exhaust note somewhat louder). Continued to have PS+PB. Turning the key back to IGN ON (no starter actuation) caused the engine to resume normal operations.

I think transman618 is confusing whether or not an AT can be “bump started” with whether the engine would remain running after having been brought up to speed. It turns out that they are two different scenarios.


#48

That test won’t work because the transmission will depower. You need to kill power to the fuel pump or something like that.
Key off = PCM off = transmission disengage.


#49

Transman618,

You are incorrect. Tried it last night in my '88 Dakota. Engine keeps turning, PS,PB keep working, engine fires up (w/o starter) when turned to ON.


#50

Back in the 1950s, most automatic transmission cars could be push started. There were instructions in the owner’s manual of my dad’s 1954 Buick on push starting the Dynaflow automatic. It didn’t apply to his car, because his had a manual transmission. In 1959, GM omitted the pump on the Hydramatic transmission, so cars equipped with this automatic (Pontiac, Oldsmobile and Cadillac) could not be push started.


#51

I hate to come across as dense but I don’t get it at this point.
In the scenario of coasting at 60 MPH with the key in RUN and the engine off what is causing the fuel pump to operate?
As far as I know the pump is inoperative at that point as a non-rotating engine is not providing an ignition pulse to the ECM.

???


#52

Just take your automatic out to a big hill and as you start down put it in 2nd or 1st and see if the engine doesn’t keep turning and holding back the vehicle.


#53

Thank Your Majesty!!


#54

QUOTE "Back in the 1950s, most automatic transmission cars could be push started. There were instructions in the owner’s manual of my dad’s 1954 Buick on push starting the Dynaflow automatic. It didn’t apply to his car, because his had a manual transmission. In 1959, GM omitted the pump on the Hydramatic transmission, so cars equipped with this automatic (Pontiac, Oldsmobile and Cadillac) could not be push started. END QUOTE

If GM took out the rear pumps then why could my 60 Buick, 61 CHEVY and 64 CHEVY be Push-started as it states it in the manual…GM removed all rear pumps in 1965 except for the powerglide which was removed after 1966 ? I have the original owners manuals for these cars and each one states how to push start an automatic…

My 59 T-bird which I still have will fire the engine at 20MPH…ignition on…when speed reaches 20 MPH drop selector to L or D2…it still works, tried it a few times.


#55

Does the 88 Dakota have a electronically controlled transmission? A modern transmission’s line pressure may be determined by the engine’s computer. Shut off the engine and the computer and the transmission may let the line pressure drop.


#56

About 10 seconds or so on my 1994 LHS from a cruise speed of around 70 MPH…


#57

If you turn the key off, then yes the transmission will disengage and the engine will stop turning and the fuel pump will stop. However, this doesn’t demonstrate what I am talking about.
I’m talking about simulating an engine stall by stopping only the fuel pump and not by turning the key off. In this case, the engine will keep turning, but it won’t be running. If you reset the fuel pump switch before you coast down below 30 or so, the engine will restart itself, because it will still be turning.

Like EllyEllis, I’m done with this thread.


#58

I recall GM didn’t suddenly remove all the rear pumps at once. It must have been a phase out, both with GM and the rest of industry. There were still some automatics that could be push started well into the 60s.


#59

It seems that I am not he only one that dissagrees with Transman.


#60

True

transman