unintended acceleration

[mfj]

So, my car has always had this problem and I have been fussing and fighting it for some time. When accelerating from a dead stop if I give it more than 1/4 throttle the gas pedal will get sucked to the floor and will not return to the idle position for 5 seconds. During this time I loose oil pressure, IE the idiot light comes on. I have slowly been eliminating problem component like; carb, vacuum advance, ignition(didn't think it would change anything), throttle cable, linkage springs. I have normal vacuum and no manifold or carb leakage. So I am not quite sure what is going on... any suggestions?

 

[wookie77]

OK, I haven't done the research to see what year it is and what type of carb? Also the oil light might be coming on if you are on the edge of being low and the acceleration is pulling the oil away from the pump. I'm sure you have checked that but just in case... I have seen later year cars have problems with the choke pull off getting stuck and I know on some quadrajet carbs they have an idle solenoid that drops the idle slowly... Not that you would have a Q-Jet unless it were a truck or police car. But just some things to think about.

 

[wookie77]

Wait!!!! You wouldn't have named your car Christine by any chance would you?????? :rolling:

I couldn't help it... It is a serious problem that could get you or someone else hurt and I would probably consider not driving the car until you can trouble shoot it... Good luck.

 

[HitIt]

Is this only when you are driving or also when you are just sitting there revving the engine?

From what you describe it's something mechanical since the pedal gets physically stuck to the floor. It's not like the pedal comes up and the carb continues to dump fuel.

First have an assistant sit in the car with the engine off and depress the pedal while you look from the outside if something is sticking.

Then I'd try taking the throttle linkage or cable off the carb. Start it up, rev it by hand at the carb and see if it does the same thing.

If it works better, again check the throttle cable and pedal pivots / linkage itself for stickiness or binding. Check the kickdown cable if your car has an auto tranny.

If it's the same, check to see that your return spring is pulling the throttle closed properly. How about the choke plate, is it stationary or loose?

 

[HitIt]

Also, maybe post up a few pics of your throttle cable, gas pedal mechanism, return spring setup, and kickdown cable. You never know, something might just be hooked up wrong.

 

[mfj]

I have a holley 4160 carb on the car, I think you're right about the low oil pressure. through research I have found some people with the same problem. Their causes and solutions are...

1)Faulty linkage- check acc cable for binding or hang up (done and checked out just fine)

2)Carb butterflies are catching on intake- (I have put two different carbs on and same same)

3) bad motor mounts- I haven't been able to check yet...I need a bigger pry bar! but doesn't everyone?

What do you think? I have a hard time imagining my motor moving sooo far that it actuates the throttle, but I have been wrong before. It could though, if the motor movement actuates the throttle... the more the throttle moves the more the motor dose as well...so some wicked awesome circular problem.

 

[mfj]

Wait!!!! You wouldn't have named your car Christine by any chance would you?????? :rolling:

I couldn't help it... It is a serious problem that could get you or someone else hurt and I would probably consider not driving the car until you can trouble shoot it... Good luck.

Sorry Boss she is my daily driver... and her name is Belle. I am a little more original than that, not that she doesn't deserve the moniker. well played.

 

[mfj]

Also, maybe post up a few pics of your throttle cable, gas pedal mechanism, return spring setup, and kickdown cable. You never know, something might just be hooked up wrong.

I'll post pics tonight after work. Thanks for the input. The problem only presents itself under load, and the linkage is bind free, I questioned the integrity of the cable so I replaced it last night and then had the episode this morning. The return springs were replaced last week, and operate properly and the choke is adjusted and working properly.

 

[HitIt]

There is a redneck way to see if your engine is moving under load- get a couple peices of string and tape them to your air cleaner and the other ends to the fenderwells with a little tension on them. Go dirve it and if they've pulled free you might have figured out that the engine is moving too much.

Also, what happens if the pedal sticks and you try to pull it up off the floor?

 

[Joe mama]

If you are using the original throttle return spring bracket with a 4160, the return spring may be overcentering. That would cause the pedal to suck to the floor. Check the way the return spring is routed. When you post your pics it will be easier to see the problem.

 

[q-ship]

Sounds like a broken drivers side motor mount.

All the symptoms you describe will result from a broken mount, including the oil light, as the sender will ground against the wiper motor as the engine lifts.

Try putting a floor jack under the drivers side of the engine, edge of oil pan (use a length of 2X4 to help distribute the weight over a larger area of the pan so you don't dent it), gently lift it about an inch or so, and you should be instantly able to see if the mount is broken. ----

---- Another way (definitely not recommended) is to open the hood so you can see the motor from the drivers seat, put the trans in low, and torque stand the car while watching the engine. if you do this, PLEASE do it on/in an open area that can accommodate several seconds of flat out acceleration with no danger. Definitely don't try it in your driveway, and keep one hand on the key so you can shut it off if it takes off, as you may very well discover that the hood is stopping it from running away for far more than 5 seconds.

If so, it will need replaced, and a torque strap will have to be installed in order to limit travel and stop the lift before the new mount breaks.

Should it not be the mount, check that you have the proper throttle cable on it, and that it is well lubed.

 

[khryslerkid]

Here is a way to check you motor mount but you have to use extreme caution! Park the car pointing away from anything you don't want to run into. With the car running hold your foot on the brake place it in gear, press on the gas gradually and have someone watch from the side of the car, not in front! to see if the engine raises up. Be prepaired to shut the car off! The fan could hit the fan shroud, the car could take off even though you are on the brakes so be ready to shut it down!

 

[khryslerkid]

q-ship you owe me a coke

 

[q-ship]

q-ship you owe me a coke

Sorry, but it's a BEER or nothing!

 

[khryslerkid]

Sorry, but it's a BEER or nothing!

:beerchug: Sounds good to me!
I had an insident with a '72 Lincoln Continental, 460ci, customers car, complained that the gas pedal was sticking. Dropped the guy off at his work place, was bringing his car back to the shop to check it out. Stopped at a intersection, waiting for the red light thought I would play around with the gas pedal. Wrong thing to do! That pedal went right to the floor, I had both feet on the brake pedal, tires smoking, I'm creeping out into the middle of the intersection, finally it hit me to reach for the key! Wow don't want to go through that again...

 

[Joe Mopar]

:beerchug: Sounds good to me!
I had an insident with a '72 Lincoln Continental, 460ci, customers car, complained that the gas pedal was sticking. Dropped the guy off at his work place, was bringing his car back to the shop to check it out. Stopped at a intersection, waiting for the red light thought I would play around with the gas pedal. Wrong thing to do! That pedal went right to the floor, I had both feet on the brake pedal, tires smoking, I'm creeping out into the middle of the intersection, finally it hit me to reach for the key! Wow don't want to go through that again...

Did you do one of these :grin: to the people staring at you from other cars, or just look for the nearest rest room? :rolling::rolling:

 

[khryslerkid]

I didn't need a restroom anymorep:

 

[mfj]

If you are using the original throttle return spring bracket with a 4160, the return spring may be overcentering. That would cause the pedal to suck to the floor. Check the way the return spring is routed. When you post your pics it will be easier to see the problem.

Sorry guy's, I couldn't get my hands on a camera last night. But I do have some pictures of the old 2 barrel carter that I took off last month. The car did it then as well, the linkage setup didn't change when I put on the Holley. except that the throttle linkage is now 1/2 an inch more towards the left. I have check the linkage again last night and we are all good, kick down works great and the throttle cable has no binding. If the car is off I can give it a quick WOT action and the throttle returns very nice and all the way. notice the spring setup on the 2-bbl, I have the same setup for the 4-bbl. Thanks for all the help guys I really appreciate it!!!!

 

[Redpolara]

It seems pretty consistant no matter what you try soooo....Is the kickdown linkage binding on something?, Have you tried it with the kickdown disconnected.

 

[mfj]

It seems pretty consistant no matter what you try soooo....Is the kickdown linkage binding on something?, Have you tried it with the kickdown disconnected.

I have drove it with the kickdown dis-connected...NOT THE THING TO DO!!! With the 727 the kickdown is very, very important. The pressure of the throttle dictates the shifting point of the trans through the kickdown linkage. If you drive it without the kickdown you will scatter your trans...it just a matter of time. I have checked and re checked the linkage for binding or hang ups and it is on the up and up. I do have an excess amount of drive line travel when I put her in gear(she clunks rather loud.) So my money is on the motor/trans mount, however I have been wrong before.