Big Trouble while driving

[matthud]

As I was on my way home today in the 69, I made a turn then gave the car some gas, went to make the 3 to 4 shift, when I took my foot off the gas to make the shift, the engine didnt drop. As I continued down the road at 50 mph without my foot on the gas I quickly discovered that I could not slow the engine down. I tried to lift up on gas pedal with my toe, but the linkage was where it was supposed to be. I finally got a chance to pull off, and as soon as I pressed the clutch the engine revved to 2500. I could not get it to slow down. I shut the car down and the engine dieseled, which it never usually does. I first checked the throttle linkage at the carb to see if it was returning to the idle screw, it was. I had to slip the clutch in 3rd gear all the way home to keep the car under control. But it really bothered me to have it constantly running at 2500 when I pulled to a stop sign.

What could have gone wrong? I checked to see if the distributor rotated on me but it was tight. So I think this is a carb issue. What should I look for?

 

[67HEAVEN]

Did the accelerator return spring break, stretch or fall off?

Have someone else start the car while you hold the throttle linkage at the carb in the idle position. If the engine idles normally, it's the linkage or return spring, or something related to that.

 

[craig32]

I had a 68 Charger (I know, please forgive me!) pull that same stunt once. It was the throttle cable, frayed out on the carb end and wouldn't retract when I let off - it stuck wide open! I was on a twisty road at the time and thought I was gonna soil the seats til I banged it in neutral and shut it down. All it needed was a new cable, hope yours is that simple.

Craig

 

[JohnZ]

Check for separation of the driver's side engine mount; with the hood open, have a friend torque it up against the brakes and see if the left side of the engine raises up.

 

[matthud]

The return spring is fine, I actually have 2 on there and they are both in fine shape. From what I can tell the throttle is returning against the idle stop screw, but its still running at 2500 rpm.

 

[jim coulter]

Have you had any vacuum lines off? Hooked mine up wrong one time and the engine would take off and race like it had a mind of its own. I'd have to kill it and then it would diesel, kinda like yours is doing. Just a thought.

 

[matthud]

I haven't made any changes to the car in about 3 weeks. And it ran fine up until midway through my drive yesterday.

 

[waterboy1976]

Is the spring on the idle screw on the carb tight...meaning.... with the right frequency vibration the screw actually turns while you have the pedal pressed . If the spring on the screw is weak it potentially could turn in at the right frequency..

 

[matthud]

Screw seems pretty tight. The carb is only about a year old.

 

[L48]

Distributor thoughts:

The vacuum advance is stuck all the way forward
The centrifugal weights under the rotor are stuck forward
The distributor is loose and got moved forward

Any one of these could increase the timing and therefore the engine speed. If your carb is on the idle stop and not leaking in extra air or fuel then the distributor is where I would look next.

 

[matthud]

The distributor isnt loose, I checked that. But could the advance or the weights really advance the engine up to 2500rpm, seems too high to be just advance in the ignition.

 

[zgator]

Check for separation of the driver's side engine mount; with the hood open, have a friend torque it up against the brakes and see if the left side of the engine raises up.

I had that happen to me on a 69 GTO.Scared the crap out of me.Took me awhile to figure out that the engine mount broke.

 

[zgator]

How is your kick down cable?