I just had a question to whom maybe could give me a solution to my problem, I am not too savvy when to comes to classic cars, but do own one. I have a 68 SS totaly restored, but I was not the one whom did the restoration. My problem is when I go to lightly press my accelerator its sometimes goes to the floor, by itself! I def was frightened the first time it happend, but it seems to release after about a couple seconds. I checked the return springs leading to the carebutor to make sure nothing was catching under the hood. Only thing that I could imagine it could be is the carebutor, but it appears to be a new one, nor did I have this problem since I owned the car for at least 3 months now. I have asked other people and they can't imagine what the problem could be. Just seeing if I could get some idea's as to what it could be, or has it ever happened to anyone?

If it's what I think it is you have a broken motor mount on the driver side of the engine... This allows the engine to lift up and push on the throttle linkage.

So having this broken motor mount would cause it to take off like that with the slightest touch? Also is there a way I can visually check to see if the motor mount is broken or not?

So having this broken motor mount would cause it to take off like that with the slightest touch? Also is there a way I can visually check to see if the motor mount is broken or not?


:yes: Yes, you step on the gas, the motor lifts and it pulls the pedal to the floor. You can verify a broken mount by opening the hood and holding your foot on the brake with the car in gear and give it a little throttle. if the motor lifts way up on the drivers side the mount is broken.

It does have the symptoms of a broken engine mount, just not sure how that would be overlooked in a car that is said to have been totally restored. Maybe a defective part.

When the 1st gens came out there where a couple accidents, and a recall....a wire rope was hooked either side of the mount bolts thru the manifold to stop this happening...since then mounts have been redesigned so is not an issue...
It sounds like broken mount...
Put a jack under the engine, lift up slowly and watch the mount see if it is broken...
The other thing could be is the linkage spline on the engine side of the firewall... right up against the fire wall....is worn or loose..

Thanks, I will definitely check it out, hopefully that will be the problem, becasue of right now she is garaged indefinitely (I'm too scared to drive her) :confused:

Back in 1969 my 68 developed that sudden acceleration and it was the motor mount.
Dealership did the wire rope as a recall and later I used the redesigned motor mounts.
Steptoe describes the safest way to check to see if the mount is broken.

becasue of right now she is garaged indefinitely (I'm too scared to drive her)
Sensable guy 10 out of 10 m8

I had the exact same thing happen to me. Yes, very scary. I was sitting at a light and took off when the light turned green. Next thing I know the pedal started to move by itself and I am squealing tires through the middle of the intersection. I was very lucky there was no one in front of me. My guess is (as others have already suggested) it's a broken engine mount on the drivers' side. I verified that it was broken engine mount on a back road with the hood open...

...since then mounts have been redesigned so is not an issue...
..

I'll definately disagree with this one. When I rebuilt my motor I put the new style mounts in. The drivers side broke last year while I was on my way to work. I was stopped at a light making a left turn. when the light changed I went to make the turn and ended up spinning doughnuts in the intersection until I could kill the ignition. Was not a fun time! This may be an isolated incident, but it can happen with the new style. I took it back to NPD when I got a replacement set and even they were surprised.

I do wonder if there are several 'versions' in the market..espec with the adventof chinese quality crap parts on the market
The new style has lugs which catch, so if broken the lift of the engine is limitted.
And when just driving around, one doesnt notice anything...till u put your boot in...
I just wonder how manty do regular maintaince and of those check thing like engine/trans mounts, brakes, brake hoses, ball joints, tie rod ends etc at each oil change....or just ass-u-me ?

I had that happen to me with a 68 327 CDN Pontiac right in front a a Police Station. I had to put a Cop in the drivers seat and told him to be prepared to turn off the ignition or I would have been charged with careless and unnecessary noise.

I knew a guy with a Straight 6 in a Pontiac Station Wagon (CDN) during the 60's with broken motor mounts and rather then replace the mounts he installed longer rad hoses so when the motor fell over it wouldn't break the hoses - One day at an intersection during rush hour a Cop directing traffic because of failed lights, waved at John to proceed and the motor jumped up and fell over - right in the middle of the intersection and stopping traffic in every direction. We immediately got out, opened the hood. When the cop saw the motor laying on its side, he started to swear. John said no problem, we will be out of your hair in a second Officer. We reached down and lifted the motor upright. I can still see the Cop waving at us to get out of his work space - LOL

GM designed a locking Motor mount and went to a Throttle Cable rather then a linkage bar to minimize the effect if mounts let go.

Wow I would have not put the two together. I had a pedal sticking to the floor problem back in the 80s. Kindof frightening until you get used to it. Now thinking about it if the motor twisted a bit the linkege would not return. I am always learning on this site. Thanks. Brian.

Well, I checked the motor mount by putting the car in gear and stomping on the accelerator and sure enough the driver side of the motor would come up a good couple of iches vice the passenger side which stayed still. Changed out the mount and did the same test and the engine stay put, then took it on a road test, and I was not friendly with the car while doing it. Sure enough it seems the problem has been rectified. I appreciate all the advice, it truly helped out a lot. I do have one more question, how come it's the driver side mount that goes bad? It seems like a few of people told me to check the driver side.

Good to hear, Dre :thumbsup:

Due to the direction of which the motor twists, it stresses the driver's side.

how come it's the driver side mount that goes bad?

Looking at the engine when you blip the throttle will answer your question - NOTE the torque force attempting to rotate the engine against the motor mounts.

Well hopefully the new mount I put it will last for some time to come, because I definitely do not want the same problem again. Thanks to everyone that gave me such great advice! I am sure I will be back again....

just a thought...If you dont want continually replace/repair...or at least reduce such things to a minumim, replace both mounts, or in the case of tie rod ends, ball joints replace in pairs..

I'd also suggest switching your throttle linkage over to cables in the near future. That way if a mount breaks, it won't pin the throttle like it does now. Either that, or get an engine strap and bolt it to the frame.

I still run my orginal factory strap..not because of orginality or safety, but that way I will not misplace or loose it lol